diff --git a/build-aux/m4/bitcoin_qt.m4 b/build-aux/m4/bitcoin_qt.m4
index 05df8621d..eb9ccbf61 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -138,6 +138,8 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
     AC_DEFINE(QT_QPA_PLATFORM_MINIMAL, 1, [Define this symbol if the minimal qt platform exists])
     if test "x$TARGET_OS" = xwindows; then
       _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)],[-lqwindows])
+      _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QMinimalIntegrationPlugin)],[-lqminimal])
++     _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QWindowsPrinterSupportPlugin)],[-lwindowsprintersupport])
       AC_DEFINE(QT_QPA_PLATFORM_WINDOWS, 1, [Define this symbol if the qt platform is windows])
     elif test "x$TARGET_OS" = xlinux; then
       _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)],[-lqxcb -lxcb-static])
@@ -359,6 +361,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_STATIC_PLUGINS],[
       if test -d "$qt_plugin_path/accessible"; then
         QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
       fi
+      QT_LIBS="$QT_LIBS -L$qt_plugin_path/printsupport"
      if test "x$use_pkgconfig" = xyes; then
      : dnl
      m4_ifdef([PKG_CHECK_MODULES],[
@@ -428,7 +431,7 @@ dnl Outputs: have_qt_test and have_qt_dbus are set (if applicable) to yes|no.
 AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
   m4_ifdef([PKG_CHECK_MODULES],[
     QT_LIB_PREFIX=Qt5
-    qt5_modules="Qt5Core Qt5Gui Qt5Network Qt5Widgets"
+    qt5_modules="Qt5Core Qt5Gui Qt5Network Qt5Widgets Qt5PrintSupport"
     BITCOIN_QT_CHECK([
       PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" have_qt=yes],[have_qt=no])
 
@@ -460,7 +463,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   TEMP_LIBS="$LIBS"
   BITCOIN_QT_CHECK([
     if test "x$qt_include_path" != x; then
-      QT_INCLUDES="-I$qt_include_path -I$qt_include_path/QtCore -I$qt_include_path/QtGui -I$qt_include_path/QtWidgets -I$qt_include_path/QtNetwork -I$qt_include_path/QtTest -I$qt_include_path/QtDBus"
+      QT_INCLUDES="-I$qt_include_path -I$qt_include_path/QtCore -I$qt_include_path/QtGui -I$qt_include_path/QtWidgets -I$qt_include_path/QtNetwork -I$qt_include_path/QtTest -I$qt_include_path/QtDBus -I$qt_include_path/QtPrintSupport"
       CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
     fi
   ])
@@ -502,6 +505,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Gui]    ,[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Gui not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Network],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Network not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Widgets],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Widgets not found)))
+  BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}PrintSupport],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}PrintSupport not found)))
   QT_LIBS="$LIBS"
   LIBS="$TEMP_LIBS"
 
diff --git a/depends/packages/bdb.mk b/depends/packages/bdb.mk
index 6c9876c2c..0b7142d9a 100644
--- a/depends/packages/bdb.mk
+++ b/depends/packages/bdb.mk
@@ -1,8 +1,8 @@
 package=bdb
-$(package)_version=4.8.30
+$(package)_version=5.1.29
 $(package)_download_path=http://download.oracle.com/berkeley-db
 $(package)_file_name=db-$($(package)_version).NC.tar.gz
-$(package)_sha256_hash=12edc0df75bf9abd7f82f821795bcee50f42cb2e5f76a6a281b85732798364ef
+$(package)_sha256_hash=08238e59736d1aacdd47cfb8e68684c695516c37f4fbe1b8267dde58dc3a576c
 $(package)_build_subdir=build_unix
 
 define $(package)_set_vars
@@ -13,8 +13,9 @@ $(package)_cxxflags=-std=c++11
 endef
 
 define $(package)_preprocess_cmds
-  sed -i.old 's/__atomic_compare_exchange/__atomic_compare_exchange_db/' dbinc/atomic.h && \
-  sed -i.old 's/atomic_init/atomic_init_db/' dbinc/atomic.h mp/mp_region.c mp/mp_mvcc.c mp/mp_fget.c mutex/mut_method.c mutex/mut_tas.c && \
+  sed -i.old 's/__atomic_compare_exchange/__atomic_compare_exchange_db/' src/dbinc/atomic.h && \
+  sed -i.old 's/atomic_init/atomic_init_db/' src/dbinc/atomic.h src/mp/mp_region.c src/mp/mp_mvcc.c src/mp/mp_fget.c src/mutex/mut_method.c src/mutex/mut_tas.c && \
+  sed -i.old 's/WinIoCtl\.h/winioctl\.h/g' src/dbinc/win_db.h && \
   cp -f $(BASEDIR)/config.guess $(BASEDIR)/config.sub dist
 endef
 
@@ -23,7 +24,7 @@ define $(package)_config_cmds
 endef
 
 define $(package)_build_cmds
-  $(MAKE) libdb_cxx-4.8.a libdb-4.8.a
+  $(MAKE) libdb_cxx-5.1.a libdb-5.1.a
 endef
 
 define $(package)_stage_cmds
diff --git a/depends/packages/openssl.mk b/depends/packages/openssl.mk
index db47113b2..e258bc222 100644
--- a/depends/packages/openssl.mk
+++ b/depends/packages/openssl.mk
@@ -1,8 +1,8 @@
 package=openssl
-$(package)_version=1.0.1k
+$(package)_version=1.0.1l
 $(package)_download_path=https://www.openssl.org/source
 $(package)_file_name=$(package)-$($(package)_version).tar.gz
-$(package)_sha256_hash=8f9faeaebad088e772f4ef5e38252d472be4d878c6b3a2718c10a4fcebe7a41c
+$(package)_sha256_hash=b2cf4d48fe5d49f240c61c9e624193a6f232b5ed0baf010681e725963c40d1d4
 
 define $(package)_set_vars
 $(package)_config_env=AR="$($(package)_ar)" RANLIB="$($(package)_ranlib)" CC="$($(package)_cc)"
diff --git a/depends/packages/qt.mk b/depends/packages/qt.mk
index 113b8dbc3..7a404e10f 100644
--- a/depends/packages/qt.mk
+++ b/depends/packages/qt.mk
@@ -7,7 +7,7 @@ $(package)_sha256_hash=eed620cb268b199bd83b3fc6a471c51d51e1dc2dbb5374fc97a0cc75f
 $(package)_dependencies=openssl zlib
 $(package)_linux_dependencies=freetype fontconfig libxcb libX11 xproto libXext
 $(package)_build_subdir=qtbase
-$(package)_qt_libs=corelib network widgets gui plugins testlib
+$(package)_qt_libs=corelib network widgets gui plugins testlib printsupport
 $(package)_patches=fix_qt_pkgconfig.patch mac-qmake.conf fix_configure_mac.patch fix_no_printer.patch fix_rcc_determinism.patch xkb-default.patch
 
 $(package)_qttranslations_file_name=qttranslations-$($(package)_suffix)
diff --git a/src/Makefile.am b/src/Makefile.am
index 0c57e6fc8..1653af522 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -92,6 +92,7 @@ endif
 BITCOIN_CORE_H = \
   addrdb.h \
   addrman.h \
+  auxpow.h \
   base58.h \
   bech32.h \
   bloom.h \
@@ -151,6 +152,7 @@ BITCOIN_CORE_H = \
   random.h \
   reverse_iterator.h \
   reverselock.h \
+  rpc/auxpow_miner.h \
   rpc/blockchain.h \
   rpc/client.h \
   rpc/mining.h \
@@ -241,6 +243,7 @@ libbitcoin_server_a_SOURCES = \
   policy/rbf.cpp \
   pow.cpp \
   rest.cpp \
+  rpc/auxpow_miner.cpp \
   rpc/blockchain.cpp \
   rpc/mining.cpp \
   rpc/misc.cpp \
@@ -353,6 +356,8 @@ libbitcoin_consensus_a_SOURCES = \
   prevector.h \
   primitives/block.cpp \
   primitives/block.h \
+  primitives/pureheader.cpp \
+  primitives/pureheader.h \
   primitives/transaction.cpp \
   primitives/transaction.h \
   pubkey.cpp \
@@ -377,6 +382,7 @@ libbitcoin_consensus_a_SOURCES = \
 libbitcoin_common_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libbitcoin_common_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_common_a_SOURCES = \
+  auxpow.cpp \
   base58.cpp \
   bech32.cpp \
   chainparams.cpp \
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 6f309f3d6..96fe2d4e6 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -32,6 +32,7 @@ BITCOIN_TESTS =\
   test/addrman_tests.cpp \
   test/amount_tests.cpp \
   test/allocator_tests.cpp \
+  test/auxpow_tests.cpp \
   test/base32_tests.cpp \
   test/base58_tests.cpp \
   test/base64_tests.cpp \
diff --git a/src/auxpow.cpp b/src/auxpow.cpp
new file mode 100644
index 000000000..208a54bec
--- /dev/null
+++ b/src/auxpow.cpp
@@ -0,0 +1,198 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2011 Vince Durham
+// Copyright (c) 2009-2014 The Bitcoin developers
+// Copyright (c) 2014-2017 Daniel Kraft
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+
+#include <auxpow.h>
+
+#include <compat/endian.h>
+#include <consensus/consensus.h>
+#include <consensus/merkle.h>
+#include <hash.h>
+#include <primitives/block.h>
+#include <script/script.h>
+#include <util.h>
+#include <utilstrencodings.h>
+
+#include <algorithm>
+#include <cassert>
+
+bool
+CAuxPow::check (const uint256& hashAuxBlock, int nChainId,
+                const Consensus::Params& params) const
+{
+    if (coinbaseTx.nIndex != 0)
+        return error("AuxPow is not a generate");
+
+    if (params.fStrictChainId && parentBlock.GetChainId () == nChainId)
+        return error("Aux POW parent has our chain ID");
+
+    if (vChainMerkleBranch.size() > 30)
+        return error("Aux POW chain merkle branch too long");
+
+    // Check that the chain merkle root is in the coinbase
+    const uint256 nRootHash
+      = CheckMerkleBranch (hashAuxBlock, vChainMerkleBranch, nChainIndex);
+    std::vector<unsigned char> vchRootHash(nRootHash.begin (), nRootHash.end ());
+    std::reverse (vchRootHash.begin (), vchRootHash.end ()); // correct endian
+
+    // Check that we are in the parent block merkle tree
+    if (CheckMerkleBranch(coinbaseTx.GetHash(), coinbaseTx.vMerkleBranch,
+                          coinbaseTx.nIndex)
+          != parentBlock.hashMerkleRoot)
+        return error("Aux POW merkle root incorrect");
+
+    const CScript script = coinbaseTx.tx->vin[0].scriptSig;
+
+    // Check that the same work is not submitted twice to our chain.
+    //
+
+    CScript::const_iterator pcHead =
+        std::search(script.begin(), script.end(), UBEGIN(pchMergedMiningHeader), UEND(pchMergedMiningHeader));
+
+    CScript::const_iterator pc =
+        std::search(script.begin(), script.end(), vchRootHash.begin(), vchRootHash.end());
+
+    if (pc == script.end())
+        return error("Aux POW missing chain merkle root in parent coinbase");
+
+    if (pcHead != script.end())
+    {
+        // Enforce only one chain merkle root by checking that a single instance of the merged
+        // mining header exists just before.
+        if (script.end() != std::search(pcHead + 1, script.end(), UBEGIN(pchMergedMiningHeader), UEND(pchMergedMiningHeader)))
+            return error("Multiple merged mining headers in coinbase");
+        if (pcHead + sizeof(pchMergedMiningHeader) != pc)
+            return error("Merged mining header is not just before chain merkle root");
+    }
+    else
+    {
+        // For backward compatibility.
+        // Enforce only one chain merkle root by checking that it starts early in the coinbase.
+        // 8-12 bytes are enough to encode extraNonce and nBits.
+        if (pc - script.begin() > 20)
+            return error("Aux POW chain merkle root must start in the first 20 bytes of the parent coinbase");
+    }
+
+
+    // Ensure we are at a deterministic point in the merkle leaves by hashing
+    // a nonce and our chain ID and comparing to the index.
+    pc += vchRootHash.size();
+    if (script.end() - pc < 8)
+        return error("Aux POW missing chain merkle tree size and nonce in parent coinbase");
+
+    uint32_t nSize;
+    memcpy(&nSize, &pc[0], 4);
+    nSize = le32toh (nSize);
+    const unsigned merkleHeight = vChainMerkleBranch.size ();
+    if (nSize != (1u << merkleHeight))
+        return error("Aux POW merkle branch size does not match parent coinbase");
+
+    uint32_t nNonce;
+    memcpy(&nNonce, &pc[4], 4);
+    nNonce = le32toh (nNonce);
+    if (nChainIndex != getExpectedIndex (nNonce, nChainId, merkleHeight))
+        return error("Aux POW wrong index");
+
+    return true;
+}
+
+int
+CAuxPow::getExpectedIndex (uint32_t nNonce, int nChainId, unsigned h)
+{
+  // Choose a pseudo-random slot in the chain merkle tree
+  // but have it be fixed for a size/nonce/chain combination.
+  //
+  // This prevents the same work from being used twice for the
+  // same chain while reducing the chance that two chains clash
+  // for the same slot.
+
+  /* This computation can overflow the uint32 used.  This is not an issue,
+     though, since we take the mod against a power-of-two in the end anyway.
+     This also ensures that the computation is, actually, consistent
+     even if done in 64 bits as it was in the past on some systems.
+
+     Note that h is always <= 30 (enforced by the maximum allowed chain
+     merkle branch length), so that 32 bits are enough for the computation.  */
+
+  uint32_t rand = nNonce;
+  rand = rand * 1103515245 + 12345;
+  rand += nChainId;
+  rand = rand * 1103515245 + 12345;
+
+  return rand % (1u << h);
+}
+
+uint256
+CAuxPow::CheckMerkleBranch (uint256 hash,
+                            const std::vector<uint256>& vMerkleBranch,
+                            int nIndex)
+{
+  if (nIndex == -1)
+    return uint256 ();
+  for (std::vector<uint256>::const_iterator it(vMerkleBranch.begin ());
+       it != vMerkleBranch.end (); ++it)
+  {
+    if (nIndex & 1)
+      hash = Hash (BEGIN (*it), END (*it), BEGIN (hash), END (hash));
+    else
+      hash = Hash (BEGIN (hash), END (hash), BEGIN (*it), END (*it));
+    nIndex >>= 1;
+  }
+  return hash;
+}
+
+std::unique_ptr<CAuxPow>
+CAuxPow::createAuxPow (const CPureBlockHeader& header)
+{
+  assert (header.IsAuxpow ());
+
+  /* Build a minimal coinbase script input for merge-mining.  */
+  const uint256 blockHash = header.GetHash ();
+  std::vector<unsigned char> inputData(blockHash.begin (), blockHash.end ());
+  std::reverse (inputData.begin (), inputData.end ());
+  inputData.push_back (1);
+  inputData.insert (inputData.end (), 7, 0);
+
+  /* Fake a parent-block coinbase with just the required input
+     script and no outputs.  */
+  CMutableTransaction coinbase;
+  coinbase.vin.resize (1);
+  coinbase.vin[0].prevout.SetNull ();
+  coinbase.vin[0].scriptSig = (CScript () << inputData);
+  assert (coinbase.vout.empty ());
+  CTransactionRef coinbaseRef = MakeTransactionRef (coinbase);
+
+  /* Build a fake parent block with the coinbase.  */
+  CBlock parent;
+  parent.nVersion = 1;
+  parent.vtx.resize (1);
+  parent.vtx[0] = coinbaseRef;
+  parent.hashMerkleRoot = BlockMerkleRoot (parent);
+
+  /* Construct the auxpow object.  */
+  std::unique_ptr<CAuxPow> auxpow(new CAuxPow (coinbaseRef));
+  assert (auxpow->vChainMerkleBranch.empty ());
+  auxpow->nChainIndex = 0;
+  assert (auxpow->coinbaseTx.vMerkleBranch.empty ());
+  auxpow->coinbaseTx.nIndex = 0;
+  auxpow->parentBlock = parent;
+
+  return auxpow;
+}
+
+CPureBlockHeader&
+CAuxPow::initAuxPow (CBlockHeader& header)
+{
+  /* Set auxpow flag right now, since we take the block hash below when creating
+     the minimal auxpow for header.  */
+  header.SetAuxpowFlag(true);
+
+  std::unique_ptr<CAuxPow> apow = createAuxPow (header);
+  CPureBlockHeader& result = apow->parentBlock;
+  header.SetAuxpow (std::move (apow));
+
+  return result;
+}
diff --git a/src/auxpow.h b/src/auxpow.h
new file mode 100644
index 000000000..a3280a19e
--- /dev/null
+++ b/src/auxpow.h
@@ -0,0 +1,204 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2014 The Bitcoin developers
+// Copyright (c) 2014-2016 Daniel Kraft
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_AUXPOW_H
+#define BITCOIN_AUXPOW_H
+
+#include <consensus/params.h>
+#include <primitives/pureheader.h>
+#include <primitives/transaction.h>
+#include <serialize.h>
+#include <uint256.h>
+
+#include <memory>
+#include <vector>
+
+class CBlock;
+class CBlockHeader;
+class CBlockIndex;
+class CValidationState;
+class UniValue;
+
+namespace auxpow_tests
+{
+class CAuxPowForTest;
+}
+
+/** Header for merge-mining data in the coinbase.  */
+static const unsigned char pchMergedMiningHeader[] = { 0xfa, 0xbe, 'm', 'm' };
+
+/* Because it is needed for auxpow, the definition of CMerkleTx is moved
+   here from wallet.h.  */
+
+/** A transaction with a merkle branch linking it to the block chain. */
+class CBaseMerkleTx
+{
+public:
+    CTransactionRef tx;
+    uint256 hashBlock;
+    std::vector<uint256> vMerkleBranch;
+
+    /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
+     * block in the chain we know this or any in-wallet dependency conflicts
+     * with. Older clients interpret nIndex == -1 as unconfirmed for backward
+     * compatibility.
+     */
+    int nIndex;
+
+    CBaseMerkleTx()
+    {
+        SetTx(MakeTransactionRef());
+        Init();
+    }
+
+    explicit CBaseMerkleTx(CTransactionRef arg)
+    {
+        SetTx(std::move(arg));
+        Init();
+    }
+
+    void Init()
+    {
+        hashBlock = uint256();
+        nIndex = -1;
+    }
+
+    void SetTx(CTransactionRef arg)
+    {
+        tx = std::move(arg);
+    }
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITE(tx);
+        READWRITE(hashBlock);
+        READWRITE(vMerkleBranch);
+        READWRITE(nIndex);
+    }
+
+    const uint256& GetHash() const { return tx->GetHash(); }
+};
+
+/**
+ * Data for the merge-mining auxpow.  This uses a merkle tx (the parent block's
+ * coinbase tx) and a manual merkle branch to link the actual Namecoin block
+ * header to the parent block header, which is mined to satisfy the PoW.
+ */
+class CAuxPow
+{
+
+private:
+
+  /**
+   * The parent block's coinbase tx, which is used to link the auxpow from
+   * the tx input to the parent block header.
+   */
+  CBaseMerkleTx coinbaseTx;
+
+  /** The merkle branch connecting the aux block to our coinbase.  */
+  std::vector<uint256> vChainMerkleBranch;
+
+  /** Merkle tree index of the aux block header in the coinbase.  */
+  int nChainIndex;
+
+  /** Parent block header (on which the real PoW is done).  */
+  CPureBlockHeader parentBlock;
+
+  /**
+   * Check a merkle branch.  This used to be in CBlock, but was removed
+   * upstream.  Thus include it here now.
+   */
+  static uint256 CheckMerkleBranch (uint256 hash,
+                                    const std::vector<uint256>& vMerkleBranch,
+                                    int nIndex);
+
+  friend UniValue AuxpowToJSON(const CAuxPow& auxpow);
+  friend class auxpow_tests::CAuxPowForTest;
+
+public:
+
+  /* Prevent accidental conversion.  */
+  inline explicit CAuxPow (CTransactionRef txIn)
+    : coinbaseTx (txIn)
+  {}
+
+  CAuxPow () = default;
+
+  ADD_SERIALIZE_METHODS;
+
+  template<typename Stream, typename Operation>
+    inline void
+    SerializationOp (Stream& s, Operation ser_action)
+  {
+    READWRITE (coinbaseTx);
+    READWRITE (vChainMerkleBranch);
+    READWRITE (nChainIndex);
+    READWRITE (parentBlock);
+  }
+
+  /**
+   * Check the auxpow, given the merge-mined block's hash and our chain ID.
+   * Note that this does not verify the actual PoW on the parent block!  It
+   * just confirms that all the merkle branches are valid.
+   * @param hashAuxBlock Hash of the merge-mined block.
+   * @param nChainId The auxpow chain ID of the block to check.
+   * @param params Consensus parameters.
+   * @return True if the auxpow is valid.
+   */
+  bool check (const uint256& hashAuxBlock, int nChainId,
+              const Consensus::Params& params) const;
+
+  /**
+   * Returns the parent block hash.  This is used to validate the PoW.
+   */
+  inline uint256
+  getParentBlockPoWHash () const
+  {
+    return parentBlock.GetPoWHash ();
+  }
+
+  /**
+   * Return parent block.  This is only used for the temporary parentblock
+   * auxpow version check.
+   * @return The parent block.
+   */
+  /* FIXME: Remove after the hardfork.  */
+  inline const CPureBlockHeader&
+  getParentBlock () const
+  {
+    return parentBlock;
+  }
+
+  /**
+   * Calculate the expected index in the merkle tree.  This is also used
+   * for the test-suite.
+   * @param nNonce The coinbase's nonce value.
+   * @param nChainId The chain ID.
+   * @param h The merkle block height.
+   * @return The expected index for the aux hash.
+   */
+  static int getExpectedIndex (uint32_t nNonce, int nChainId, unsigned h);
+
+  /**
+   * Constructs a minimal CAuxPow object for the given block header and
+   * returns it.  The caller should make sure to set the auxpow flag on the
+   * header already, since the block hash to which the auxpow commits depends
+   * on that!
+   */
+  static std::unique_ptr<CAuxPow> createAuxPow (const CPureBlockHeader& header);
+
+  /**
+   * Initialises the auxpow of the given block header.  This builds a minimal
+   * auxpow object like createAuxPow and sets it on the block header.  Returns
+   * a reference to the parent header so it can be mined as a follow-up.
+   */
+  static CPureBlockHeader& initAuxPow (CBlockHeader& header);
+
+};
+
+#endif // BITCOIN_AUXPOW_H
diff --git a/src/chain.cpp b/src/chain.cpp
index d462f94ab..5cb09f6fc 100644
--- a/src/chain.cpp
+++ b/src/chain.cpp
@@ -4,6 +4,34 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chain.h>
+#include <validation.h>
+
+using namespace std;
+
+/* Moved here from the header, because we need auxpow and the logic
+   becomes more involved.  */
+CBlockHeader CBlockIndex::GetBlockHeader(const Consensus::Params& consensusParams) const
+{
+    CBlockHeader block;
+
+    /* The CBlockIndex object's block header is missing the auxpow.
+       So if this is an auxpow block, read it from disk instead.  We only
+       have to read the actual *header*, not the full block.  */
+    if (block.IsAuxpow())
+    {
+        ReadBlockHeaderFromDisk(block, this, consensusParams);
+        return block;
+    }
+
+    block.nVersion       = nVersion;
+    if (pprev)
+        block.hashPrevBlock = pprev->GetBlockHash();
+    block.hashMerkleRoot = hashMerkleRoot;
+    block.nTime          = nTime;
+    block.nBits          = nBits;
+    block.nNonce         = nNonce;
+    return block;
+}
 
 /**
  * CChain implementation
diff --git a/src/chain.h b/src/chain.h
index 34879d576..ca10f4449 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -213,9 +213,6 @@ public:
     uint32_t nBits;
     uint32_t nNonce;
 
-    // Dogecoin: Keep the Scrypt hash as well as SHA256
-    uint256 hashBlockPoW;
-
     //! (memory only) Sequential id assigned to distinguish order in which blocks are received.
     int32_t nSequenceId;
 
@@ -243,7 +240,6 @@ public:
         nTime          = 0;
         nBits          = 0;
         nNonce         = 0;
-        hashBlockPoW   = uint256();
     }
 
     CBlockIndex()
@@ -260,7 +256,6 @@ public:
         nTime          = block.nTime;
         nBits          = block.nBits;
         nNonce         = block.nNonce;
-        hashBlockPoW   = block.GetPoWHash();
     }
 
     CDiskBlockPos GetBlockPos() const {
@@ -281,29 +276,13 @@ public:
         return ret;
     }
 
-    CBlockHeader GetBlockHeader() const
-    {
-        CBlockHeader block;
-        block.nVersion       = nVersion;
-        if (pprev)
-            block.hashPrevBlock = pprev->GetBlockHash();
-        block.hashMerkleRoot = hashMerkleRoot;
-        block.nTime          = nTime;
-        block.nBits          = nBits;
-        block.nNonce         = nNonce;
-        return block;
-    }
+    CBlockHeader GetBlockHeader(const Consensus::Params& consensusParams) const;
 
     uint256 GetBlockHash() const
     {
         return *phashBlock;
     }
 
-    uint256 GetBlockPoWHash() const
-    {
-        return hashBlockPoW;
-    }
-
     int64_t GetBlockTime() const
     {
         return (int64_t)nTime;
@@ -367,6 +346,13 @@ public:
     //! Efficiently find an ancestor of this block.
     CBlockIndex* GetAncestor(int height);
     const CBlockIndex* GetAncestor(int height) const;
+
+    /* Analyse the block version.  */
+    inline int GetBaseVersion() const
+    {
+        return CPureBlockHeader::GetBaseVersion(nVersion);
+    }
+
 };
 
 arith_uint256 GetBlockProof(const CBlockIndex& block);
@@ -415,7 +401,6 @@ public:
         READWRITE(nTime);
         READWRITE(nBits);
         READWRITE(nNonce);
-        READWRITE(hashBlockPoW);
     }
 
     uint256 GetBlockHash() const
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 830dd2f91..ca0ed3982 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -109,7 +109,11 @@ public:
         // By default assume that the signatures in ancestors of this block are valid.
         consensus.defaultAssumeValid = uint256S("0x0000000000000000002e63058c023a9a1de233554f28c7b21380b6c9003f36a8"); //534292
 
-        /**
+        consensus.nAuxpowChainId = 0x0062; // 98 - Josh Wise!
+        consensus.nAuxpowStartHeight = 371337;
+        consensus.fStrictChainId = true;
+        consensus.nLegacyBlocksBefore = 371337;
+        /** 
          * The message start string is designed to be unlikely to occur in normal data.
          * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
          * a large 32-bit integer with any alignment.
@@ -122,6 +126,7 @@ public:
         nPruneAfterHeight = 100000;
 
         genesis = CreateGenesisBlock(1386325540, 99943, 0x1e0ffff0, 1, 88 * COIN);
+
         consensus.hashGenesisBlock = genesis.GetHash();
         assert(consensus.hashGenesisBlock == uint256S("0x1a91e3dace36e2be3bf030a65679fe821aa1d6ef92e7c9902eb318182c355691"));
         assert(genesis.hashMerkleRoot == uint256S("0x5b2a3f53f605d62c53e62932dac6925e3d74afa5a4b459745c36d42d0ed26a69"));
@@ -222,6 +227,10 @@ public:
         // By default assume that the signatures in ancestors of this block are valid.
         consensus.defaultAssumeValid = uint256S("0x0000000000000037a8cd3e06cd5edbfe9dd1dbcc5dacab279376ef7cfc2b4c75"); //1354312
 
+        consensus.nAuxpowStartHeight = 158100;
+        consensus.fStrictChainId = false;
+        consensus.nLegacyBlocksBefore = -1;
+
         pchMessageStart[0] = 0xfc;
         pchMessageStart[1] = 0xc1;
         pchMessageStart[2] = 0xb7;
@@ -312,6 +321,8 @@ public:
         // By default assume that the signatures in ancestors of this block are valid.
         consensus.defaultAssumeValid = uint256S("0x00");
 
+        consensus.fStrictChainId = true;
+        consensus.nLegacyBlocksBefore = 0;
         pchMessageStart[0] = 0xfa;
         pchMessageStart[1] = 0xbf;
         pchMessageStart[2] = 0xb5;
diff --git a/src/chainparams.h b/src/chainparams.h
index 722e52ff4..d95c471a3 100644
--- a/src/chainparams.h
+++ b/src/chainparams.h
@@ -81,6 +81,7 @@ public:
     const CCheckpointData& Checkpoints() const { return checkpointData; }
     const ChainTxData& TxData() const { return chainTxData; }
     void UpdateVersionBitsParameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout);
+
 protected:
     CChainParams() {}
 
diff --git a/src/consensus/params.h b/src/consensus/params.h
index 6c3a201f4..ff90b1304 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -75,6 +75,24 @@ struct Params {
     int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
     uint256 nMinimumChainWork;
     uint256 defaultAssumeValid;
+
+    /** Auxpow parameters */
+    int32_t nAuxpowChainId;
+    int nAuxpowStartHeight;
+    bool fStrictChainId;
+    int nLegacyBlocksBefore; // -1 for "always allow"
+
+    /**
+     * Check whether or not to allow legacy blocks at the given height.
+     * @param nHeight Height of the block to check.
+     * @return True if it is allowed to have a legacy version.
+     */
+    bool AllowLegacyBlocks(unsigned nHeight) const
+    {
+        if (nLegacyBlocksBefore < 0)
+            return true;
+        return static_cast<int> (nHeight) < nLegacyBlocksBefore;
+    }
 };
 } // namespace Consensus
 
diff --git a/src/dogecoin.cpp b/src/dogecoin.cpp
index 77a8a0093..396c4cbc4 100644
--- a/src/dogecoin.cpp
+++ b/src/dogecoin.cpp
@@ -5,7 +5,10 @@
 #include <boost/random/uniform_int.hpp>
 #include <boost/random/mersenne_twister.hpp>
 
-#include "dogecoin.h"
+#include <arith_uint256.h>
+#include <dogecoin.h>
+#include <pow.h>
+#include <util.h>
 
 int static generateMTRandom(unsigned int s, int range)
 {
@@ -14,6 +17,121 @@ int static generateMTRandom(unsigned int s, int range)
     return dist(gen);
 }
 
+// Dogecoin: Normally minimum difficulty blocks can only occur in between
+// retarget blocks. However, once we introduce Digishield every block is
+// a retarget, so we need to handle minimum difficulty on all blocks.
+bool AllowDigishieldMinDifficultyForBlock(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
+{
+    // check if the chain allows minimum difficulty blocks
+    if (!params.fPowAllowMinDifficultyBlocks)
+        return false;
+
+    // check if the chain allows minimum difficulty blocks on recalc blocks
+    if (pindexLast->nHeight < 157500)
+    // if (!params.fPowAllowDigishieldMinDifficultyBlocks)
+        return false;
+
+    // Allow for a minimum block time if the elapsed time > 2*nTargetSpacing
+    return (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2);
+}
+
+unsigned int CalculateDogecoinNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
+{
+    int nHeight = pindexLast->nHeight + 1;
+    bool fNewDifficultyProtocol = (nHeight >= 145000);
+    // bool fNewDifficultyProtocol = (nHeight >= params.GetDigiShieldForkBlock());
+    const int64_t retargetTimespan = fNewDifficultyProtocol ? 60 // params.DigiShieldTargetTimespan()
+                                                              :
+                                                              params.nPowTargetTimespan;
+
+    const int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
+    int64_t nModulatedTimespan = nActualTimespan;
+    int64_t nMaxTimespan;
+    int64_t nMinTimespan;
+
+    if (fNewDifficultyProtocol) //DigiShield implementation - thanks to RealSolid & WDC for this code
+    {
+        // amplitude filter - thanks to daft27 for this code
+        nModulatedTimespan = retargetTimespan + (nModulatedTimespan - retargetTimespan) / 8;
+
+        nMinTimespan = retargetTimespan - (retargetTimespan / 4);
+        nMaxTimespan = retargetTimespan + (retargetTimespan / 2);
+    } else if (nHeight > 10000) {
+        nMinTimespan = retargetTimespan / 4;
+        nMaxTimespan = retargetTimespan * 4;
+    } else if (nHeight > 5000) {
+        nMinTimespan = retargetTimespan / 8;
+        nMaxTimespan = retargetTimespan * 4;
+    } else {
+        nMinTimespan = retargetTimespan / 16;
+        nMaxTimespan = retargetTimespan * 4;
+    }
+
+    // Limit adjustment step
+    if (nModulatedTimespan < nMinTimespan)
+        nModulatedTimespan = nMinTimespan;
+    else if (nModulatedTimespan > nMaxTimespan)
+        nModulatedTimespan = nMaxTimespan;
+
+    // Retarget
+    const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
+    arith_uint256 bnNew;
+    arith_uint256 bnOld;
+    bnNew.SetCompact(pindexLast->nBits);
+    bnOld = bnNew;
+    bnNew *= nModulatedTimespan;
+    bnNew /= retargetTimespan;
+
+    if (bnNew > bnPowLimit)
+        bnNew = bnPowLimit;
+
+    /// debug print
+    LogPrintf("GetNextWorkRequired RETARGET\n");
+    LogPrintf("params.nPowTargetTimespan = %d    nActualTimespan = %d\n", params.nPowTargetTimespan, nActualTimespan);
+    LogPrintf("Before: %08x  %s\n", pindexLast->nBits, bnOld.ToString());
+    LogPrintf("After:  %08x  %s\n", bnNew.GetCompact(), bnNew.ToString());
+
+    return bnNew.GetCompact();
+}
+
+bool CheckAuxPowProofOfWork(const CBlockHeader& block, const Consensus::Params& params)
+{
+    /* Except for legacy blocks with full version 1, ensure that
+       the chain ID is correct.  Legacy blocks are not allowed since
+       the merge-mining start, which is checked in AcceptBlockHeader
+       where the height is known.  */
+    if (!block.IsLegacy() && params.fStrictChainId
+        && block.GetChainId() != params.nAuxpowChainId)
+        return error("%s : block does not have our chain ID"
+                     " (got %d, expected %d, full nVersion %d)",
+                     __func__, block.GetChainId(),
+                     params.nAuxpowChainId, block.nVersion);
+
+    /* If there is no auxpow, just check the block hash.  */
+    if (!block.auxpow) {
+        if (block.IsAuxpow())
+            return error("%s : no auxpow on block with auxpow version",
+                         __func__);
+
+        if (!CheckProofOfWork(block.GetPoWHash(), block.nBits, params))
+            return error("%s : non-AUX proof of work failed", __func__);
+
+        return true;
+    }
+
+    /* We have auxpow.  Check it.  */
+
+    if (!block.IsAuxpow())
+        return error("%s : auxpow on block with non-auxpow version", __func__);
+
+    if (!block.auxpow->check(block.GetHash(), block.GetChainId(), params))
+        return error("%s : AUX POW is not valid", __func__);
+    if (!CheckProofOfWork(block.auxpow->getParentBlockPoWHash(), block.nBits, params))
+        return error("%s : AUX proof of work failed", __func__);
+
+    return true;
+}
+
 CAmount GetDogecoinBlockSubsidy(int nHeight, const Consensus::Params& consensusParams, uint256 prevHash)
 {
     int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
diff --git a/src/dogecoin.h b/src/dogecoin.h
index d834372a0..403673da5 100644
--- a/src/dogecoin.h
+++ b/src/dogecoin.h
@@ -2,7 +2,18 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include "chainparams.h"
 #include "amount.h"
+#include "chain.h"
+#include "chainparams.h"
 
+bool AllowDigishieldMinDifficultyForBlock(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params);
 CAmount GetDogecoinBlockSubsidy(int nHeight, const Consensus::Params& consensusParams, uint256 prevHash);
+unsigned int CalculateDogecoinNextWorkRequired(const CBlockIndex* pindexLast, int64_t nLastRetargetTime, const Consensus::Params& params);
+
+/**
+ * Check proof-of-work of a block header, taking auxpow into account.
+ * @param block The block header.
+ * @param params Consensus parameters.
+ * @return True iff the PoW is correct.
+ */
+bool CheckAuxPowProofOfWork(const CBlockHeader& block, const Consensus::Params& params);
diff --git a/src/init.cpp b/src/init.cpp
index 88bfbcff0..9f9e47e78 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -29,6 +29,8 @@
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
+#include <rpc/auxpow_miner.h>
+#include <rpc/mining.h>
 #include <rpc/server.h>
 #include <rpc/register.h>
 #include <rpc/blockchain.h>
@@ -211,6 +213,10 @@ void Shutdown()
     if (g_connman) g_connman->Stop();
     if (g_txindex) g_txindex->Stop();
 
+    if (g_auxpow_miner != nullptr) {
+        g_auxpow_miner.reset();
+    }
+
     StopTorControl();
 
     // After everything has been shut down, but before things get flushed, stop the
@@ -1281,6 +1287,8 @@ bool AppInitMain()
     RegisterZMQRPCCommands(tableRPC);
 #endif
 
+    g_auxpow_miner.reset(new AuxpowMiner());
+
     /* Start the RPC server already.  It will be started in "warmup" mode
      * and not really process calls already (but it will signify connections
      * that the server is there and will be ready later).  Warmup mode will
diff --git a/src/miner.cpp b/src/miner.cpp
index 04476b037..04f43792b 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -36,6 +36,7 @@
 // its ancestors.
 
 uint64_t nLastBlockTx = 0;
+uint64_t nLastBlockSize = 0;
 uint64_t nLastBlockWeight = 0;
 
 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
@@ -88,6 +89,7 @@ void BlockAssembler::resetBlock()
     inBlock.clear();
 
     // Reserve space for coinbase tx
+    nBlockSize = 1000;
     nBlockWeight = 4000;
     nBlockSigOpsCost = 400;
     fIncludeWitness = false;
@@ -119,11 +121,15 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     assert(pindexPrev != nullptr);
     nHeight = pindexPrev->nHeight + 1;
 
-    pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
+    const int32_t nChainId = chainparams.GetConsensus ().nAuxpowChainId;
+    // FIXME: Active version bits after the always-auxpow fork!
+    //const int32_t nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
+    const int32_t nVersion = 4;
+    pblock->SetBaseVersion(nVersion, nChainId);
     // -regtest only: allow overriding block.nVersion with
     // -blockversion=N to test forking scenarios
     if (chainparams.MineBlocksOnDemand())
-        pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
+        pblock->SetBaseVersion(gArgs.GetArg("-blockversion", pblock->GetBaseVersion()), nChainId);
 
     pblock->nTime = GetAdjustedTime();
     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
@@ -150,6 +156,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     int64_t nTime1 = GetTimeMicros();
 
     nLastBlockTx = nBlockTx;
+    nLastBlockSize = nBlockSize;
     nLastBlockWeight = nBlockWeight;
 
     // Create coinbase transaction.
@@ -165,7 +172,8 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
     pblocktemplate->vTxFees[0] = -nFees;
 
-    LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
+    uint64_t nSerializeSize = GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION);
+    LogPrintf("CreateNewBlock(): total size: %u block weight: %u txs: %u fees: %ld sigops %d\n", nSerializeSize, GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 
     // Fill in header
     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
@@ -212,6 +220,8 @@ bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost
 // - transaction finality (locktime)
 // - premature witness (in case segwit transactions are added to mempool before
 //   segwit activation)
+// - serialized size (in case -blockmaxsize is in use)
+// - Namecoin maturity conditions
 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 {
     for (CTxMemPool::txiter it : package) {
diff --git a/src/miner.h b/src/miner.h
index 8cdcf7133..a2d6b6b5f 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -132,10 +132,12 @@ private:
     // Configuration parameters for the block size
     bool fIncludeWitness;
     unsigned int nBlockMaxWeight;
+    bool fNeedSizeAccounting;
     CFeeRate blockMinFeeRate;
 
     // Information on the current status of the block
     uint64_t nBlockWeight;
+    uint64_t nBlockSize;
     uint64_t nBlockTx;
     uint64_t nBlockSigOpsCost;
     CAmount nFees;
@@ -196,5 +198,6 @@ private:
 /** Modify the extranonce in a block */
 void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce);
 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev);
+bool ProcessBlockFound(const CBlock* pblock, const CChainParams& chainParams);
 
 #endif // BITCOIN_MINER_H
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 582d9fcad..bf6cb77c1 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -2180,7 +2180,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         LogPrint(BCLog::NET, "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), pfrom->GetId());
         for (; pindex; pindex = chainActive.Next(pindex))
         {
-            vHeaders.push_back(pindex->GetBlockHeader());
+            vHeaders.push_back(pindex->GetBlockHeader(chainparams.GetConsensus()));
             if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                 break;
         }
@@ -3423,14 +3423,14 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
                     pBestIndex = pindex;
                     if (fFoundStartingHeader) {
                         // add this to the headers message
-                        vHeaders.push_back(pindex->GetBlockHeader());
+                        vHeaders.push_back(pindex->GetBlockHeader(consensusParams));
                     } else if (PeerHasHeader(&state, pindex)) {
                         continue; // keep looking for the first new block
                     } else if (pindex->pprev == nullptr || PeerHasHeader(&state, pindex->pprev)) {
                         // Peer doesn't have this header but they do have the prior one.
                         // Start sending headers.
                         fFoundStartingHeader = true;
-                        vHeaders.push_back(pindex->GetBlockHeader());
+                        vHeaders.push_back(pindex->GetBlockHeader(consensusParams));
                     } else {
                         // Peer doesn't have this header or the prior one -- nothing will
                         // connect, so bail out.
diff --git a/src/policy/policy.h b/src/policy/policy.h
index 3d47ac126..7a45ec0f6 100644
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -16,8 +16,10 @@
 class CCoinsViewCache;
 class CTxOut;
 
+/** Default for -blockmaxsize, which controls the maximum size of block the mining code will create **/
+static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
 /** Default for -blockmaxweight, which controls the range of block weights the mining code will create **/
-static const unsigned int DEFAULT_BLOCK_MAX_WEIGHT = MAX_BLOCK_WEIGHT - 4000;
+static const unsigned int DEFAULT_BLOCK_MAX_WEIGHT = 3000000;
 /** Default for -blockmintxfee, which sets the minimum feerate for a transaction in blocks created by mining code **/
 static const unsigned int DEFAULT_BLOCK_MIN_TX_FEE = 1000;
 /** The maximum weight for transactions we're willing to relay/mine */
diff --git a/src/pow.cpp b/src/pow.cpp
index ab305649a..09e38cef0 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -5,8 +5,10 @@
 
 #include <pow.h>
 
+#include <auxpow.h>
 #include <arith_uint256.h>
 #include <chain.h>
+#include <dogecoin.h>
 #include <primitives/block.h>
 #include <uint256.h>
 #include <util.h>
@@ -16,8 +18,21 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     assert(pindexLast != nullptr);
     unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
 
+    // Dogecoin: Special rules for minimum difficulty blocks with Digishield
+    if (AllowDigishieldMinDifficultyForBlock(pindexLast, pblock, params))
+    {
+        // Special difficulty rule for testnet:
+        // If the new block's timestamp is more than 2* nTargetSpacing minutes
+        // then allow mining of a min-difficulty block.
+        return nProofOfWorkLimit;
+    }
+
     // Only change once per difficulty adjustment interval
-    if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
+    bool fNewDifficultyProtocol = (pindexLast->nHeight >= 145000);
+    const int64_t difficultyAdjustmentInterval = fNewDifficultyProtocol
+                                                 ? 1
+                                                 : params.DifficultyAdjustmentInterval();
+    if ((pindexLast->nHeight+1) % difficultyAdjustmentInterval != 0)
     {
         if (params.fPowAllowMinDifficultyBlocks)
         {
@@ -40,9 +55,9 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
 
     // Litecoin: This fixes an issue where a 51% attack can change difficulty at will.
     // Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
-    int blockstogoback = params.DifficultyAdjustmentInterval()-1;
-    if ((pindexLast->nHeight+1) != params.DifficultyAdjustmentInterval())
-        blockstogoback = params.DifficultyAdjustmentInterval();
+    int blockstogoback = difficultyAdjustmentInterval-1;
+    if ((pindexLast->nHeight+1) != difficultyAdjustmentInterval)
+        blockstogoback = difficultyAdjustmentInterval;
 
     // Go back by what we want to be 14 days worth of blocks
     int nHeightFirst = pindexLast->nHeight - blockstogoback;
@@ -50,7 +65,7 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     const CBlockIndex* pindexFirst = pindexLast->GetAncestor(nHeightFirst);
     assert(pindexFirst);
 
-    return CalculateNextWorkRequired(pindexLast, pindexFirst->GetBlockTime(), params);
+    return CalculateDogecoinNextWorkRequired(pindexLast, pindexFirst->GetBlockTime(), params);
 }
 
 unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
diff --git a/src/primitives/block.cpp b/src/primitives/block.cpp
index c61dc5fb5..f272347a3 100644
--- a/src/primitives/block.cpp
+++ b/src/primitives/block.cpp
@@ -6,21 +6,21 @@
 #include <primitives/block.h>
 
 #include <hash.h>
-#include <crypto/scrypt.h>
 #include <tinyformat.h>
 #include <utilstrencodings.h>
 #include <crypto/common.h>
 
-uint256 CBlockHeader::GetHash() const
+void CBlockHeader::SetAuxpow (std::unique_ptr<CAuxPow> apow)
 {
-    return SerializeHash(*this);
-}
-
-uint256 CBlockHeader::GetPoWHash() const
-{
-    uint256 thash;
-    scrypt_1024_1_1_256(BEGIN(nVersion), BEGIN(thash));
-    return thash;
+    if (apow != nullptr)
+    {
+        auxpow.reset(apow.release());
+        SetAuxpowFlag(true);
+    } else
+    {
+        auxpow.reset();
+        SetAuxpowFlag(false);
+    }
 }
 
 std::string CBlock::ToString() const
diff --git a/src/primitives/block.h b/src/primitives/block.h
index 9bc06ad6b..1c3243bb3 100644
--- a/src/primitives/block.h
+++ b/src/primitives/block.h
@@ -6,10 +6,14 @@
 #ifndef BITCOIN_PRIMITIVES_BLOCK_H
 #define BITCOIN_PRIMITIVES_BLOCK_H
 
+#include <auxpow.h>
 #include <primitives/transaction.h>
+#include <primitives/pureheader.h>
 #include <serialize.h>
 #include <uint256.h>
 
+#include <memory>
+
 /** Nodes collect new transactions into a block, hash them into a hash tree,
  * and scan through nonce values to make the block's hash satisfy proof-of-work
  * requirements.  When they solve the proof-of-work, they broadcast the block
@@ -17,16 +21,12 @@
  * in the block is a special one that creates a new coin owned by the creator
  * of the block.
  */
-class CBlockHeader
+class CBlockHeader : public CPureBlockHeader
 {
 public:
-    // header
-    int32_t nVersion;
-    uint256 hashPrevBlock;
-    uint256 hashMerkleRoot;
-    uint32_t nTime;
-    uint32_t nBits;
-    uint32_t nNonce;
+
+    // auxpow (if this is a merge-minded block)
+    std::shared_ptr<CAuxPow> auxpow;
 
     CBlockHeader()
     {
@@ -37,37 +37,29 @@ public:
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action) {
-        READWRITE(this->nVersion);
-        READWRITE(hashPrevBlock);
-        READWRITE(hashMerkleRoot);
-        READWRITE(nTime);
-        READWRITE(nBits);
-        READWRITE(nNonce);
+        READWRITE(*(CPureBlockHeader*)this);
+
+        if (this->IsAuxpow())
+        {
+            if (ser_action.ForRead())
+                auxpow = std::make_shared<CAuxPow>();
+            assert(auxpow != nullptr);
+            READWRITE(*auxpow);
+        } else if (ser_action.ForRead())
+            auxpow.reset();
     }
 
     void SetNull()
     {
-        nVersion = 0;
-        hashPrevBlock.SetNull();
-        hashMerkleRoot.SetNull();
-        nTime = 0;
-        nBits = 0;
-        nNonce = 0;
+        CPureBlockHeader::SetNull();
+        auxpow.reset();
     }
 
-    bool IsNull() const
-    {
-        return (nBits == 0);
-    }
-
-    uint256 GetHash() const;
-
-    uint256 GetPoWHash() const;
-
-    int64_t GetBlockTime() const
-    {
-        return (int64_t)nTime;
-    }
+    /**
+     * Set the block's auxpow (or unset it).  This takes care of updating
+     * the version accordingly.
+     */
+    void SetAuxpow (std::unique_ptr<CAuxPow> apow);
 };
 
 
@@ -115,6 +107,7 @@ public:
         block.nTime          = nTime;
         block.nBits          = nBits;
         block.nNonce         = nNonce;
+        block.auxpow         = auxpow;
         return block;
     }
 
diff --git a/src/primitives/pureheader.cpp b/src/primitives/pureheader.cpp
new file mode 100644
index 000000000..2dc33d738
--- /dev/null
+++ b/src/primitives/pureheader.cpp
@@ -0,0 +1,29 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2014 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "primitives/pureheader.h"
+
+#include "crypto/scrypt.h"
+#include "hash.h"
+#include "utilstrencodings.h"
+
+void CPureBlockHeader::SetBaseVersion(int32_t nBaseVersion, int32_t nChainId)
+{
+    assert(nBaseVersion >= 1 && nBaseVersion < VERSION_AUXPOW);
+    assert(!IsAuxpow());
+    nVersion = nBaseVersion | (nChainId * VERSION_CHAIN_START);
+}
+
+uint256 CPureBlockHeader::GetHash() const
+{
+    return SerializeHash(*this);
+}
+
+uint256 CPureBlockHeader::GetPoWHash() const
+{
+    uint256 thash;
+    scrypt_1024_1_1_256(BEGIN(nVersion), BEGIN(thash));
+    return thash;
+}
diff --git a/src/primitives/pureheader.h b/src/primitives/pureheader.h
new file mode 100644
index 000000000..34373bbb7
--- /dev/null
+++ b/src/primitives/pureheader.h
@@ -0,0 +1,157 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2013 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PRIMITIVES_PUREHEADER_H
+#define BITCOIN_PRIMITIVES_PUREHEADER_H
+
+#include "serialize.h"
+#include "uint256.h"
+
+/**
+ * A block header without auxpow information.  This "intermediate step"
+ * in constructing the full header is useful, because it breaks the cyclic
+ * dependency between auxpow (referencing a parent block header) and
+ * the block header (referencing an auxpow).  The parent block header
+ * does not have auxpow itself, so it is a pure header.
+ */
+class CPureBlockHeader
+{
+public:
+
+    /* Modifiers to the version.  */
+    static const int32_t VERSION_AUXPOW = (1 << 8);
+
+    /** Bits above are reserved for the auxpow chain ID.  */
+    static const int32_t VERSION_CHAIN_START = (1 << 16);
+
+    // header
+    int32_t nVersion;
+    uint256 hashPrevBlock;
+    uint256 hashMerkleRoot;
+    uint32_t nTime;
+    uint32_t nBits;
+    uint32_t nNonce;
+
+    CPureBlockHeader()
+    {
+        SetNull();
+    }
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITE(this->nVersion);
+        READWRITE(hashPrevBlock);
+        READWRITE(hashMerkleRoot);
+        READWRITE(nTime);
+        READWRITE(nBits);
+        READWRITE(nNonce);
+    }
+
+    void SetNull()
+    {
+        nVersion = 0;
+        hashPrevBlock.SetNull();
+        hashMerkleRoot.SetNull();
+        nTime = 0;
+        nBits = 0;
+        nNonce = 0;
+    }
+
+    bool IsNull() const
+    {
+        return (nBits == 0);
+    }
+
+    uint256 GetHash() const;
+    uint256 GetPoWHash() const;
+
+    int64_t GetBlockTime() const
+    {
+        return (int64_t)nTime;
+    }
+
+    /* Below are methods to interpret the version with respect to
+       auxpow data and chain ID.  This used to be in the CBlockVersion
+       class, but was moved here when we switched back to nVersion being
+       a pure int member as preparation to undoing the "abuse" and
+       allowing BIP9 to work.  */
+
+    /**
+     * Extract the base version (without modifiers and chain ID).
+     * @return The base version./
+     */
+    inline int32_t GetBaseVersion() const
+    {
+        return GetBaseVersion(nVersion);
+    }
+    static inline int32_t GetBaseVersion(int32_t ver)
+    {
+        return ver % VERSION_AUXPOW;
+    }
+
+    /**
+     * Set the base version (apart from chain ID and auxpow flag) to
+     * the one given.  This should only be called when auxpow is not yet
+     * set, to initialise a block!
+     * @param nBaseVersion The base version.
+     * @param nChainId The auxpow chain ID.
+     */
+    void SetBaseVersion(int32_t nBaseVersion, int32_t nChainId);
+
+    /**
+     * Extract the chain ID.
+     * @return The chain ID encoded in the version.
+     */
+    inline int32_t GetChainId() const
+    {
+        return nVersion >> 16;
+    }
+
+    /**
+     * Set the chain ID.  This is used for the test suite.
+     * @param ch The chain ID to set.
+     */
+    inline void SetChainId(int32_t chainId)
+    {
+        nVersion %= VERSION_CHAIN_START;
+        nVersion |= chainId * VERSION_CHAIN_START;
+    }
+
+    /**
+     * Check if the auxpow flag is set in the version.
+     * @return True iff this block version is marked as auxpow.
+     */
+    inline bool IsAuxpow() const
+    {
+        return nVersion & VERSION_AUXPOW;
+    }
+
+    /**
+     * Set the auxpow flag.  This is used for testing.
+     * @param auxpow Whether to mark auxpow as true.
+     */
+    inline void SetAuxpowFlag(bool auxpow)
+    {
+        if (auxpow)
+            nVersion |= VERSION_AUXPOW;
+        else
+            nVersion &= ~VERSION_AUXPOW;
+    }
+
+    /**
+     * Check whether this is a "legacy" block without chain ID.
+     * @return True iff it is.
+     */
+    inline bool IsLegacy() const
+    {
+        return nVersion == 1
+            // Dogecoin: We have a random v2 block with no AuxPoW, treat as legacy
+            || (nVersion == 2 && GetChainId() == 0);
+    }
+};
+
+#endif // BITCOIN_PRIMITIVES_PUREHEADER_H
diff --git a/src/qt/test/addressbooktests.cpp b/src/qt/test/addressbooktests.cpp
index 352584604..6760b0786 100644
--- a/src/qt/test/addressbooktests.cpp
+++ b/src/qt/test/addressbooktests.cpp
@@ -56,7 +56,7 @@ void EditAddressAndSubmit(
  */
 void TestAddAddressesToSendBook()
 {
-    TestChain100Setup test;
+    TestChain240Setup test;
     std::shared_ptr<CWallet> wallet = std::make_shared<CWallet>("mock", WalletDatabase::CreateMock());
     bool firstRun;
     wallet->LoadWallet(firstRun);
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index a5b9dd722..61c35b531 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -128,7 +128,7 @@ void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, st
 //     src/qt/test/test_bitcoin-qt -platform cocoa    # macOS
 void TestGUI()
 {
-    // Set up wallet and chain with 105 blocks (5 mature blocks for spending).
+    // Set up wallet and chain with 245 blocks (5 mature blocks for spending).
     TestChain240Setup test;
     for (int i = 0; i < 5; ++i) {
         test.CreateAndProcessBlock({}, GetScriptForRawPubKey(test.coinbaseKey.GetPubKey()));
diff --git a/src/rest.cpp b/src/rest.cpp
index b81a6f9c5..56ce83098 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -157,9 +157,10 @@ static bool rest_headers(HTTPRequest* req,
         }
     }
 
+    const CChainParams& chainparams = Params();
     CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
     for (const CBlockIndex *pindex : headers) {
-        ssHeader << pindex->GetBlockHeader();
+        ssHeader << pindex->GetBlockHeader(chainparams.GetConsensus());
     }
 
     switch (rf) {
diff --git a/src/rpc/auxpow_miner.cpp b/src/rpc/auxpow_miner.cpp
new file mode 100644
index 000000000..3d6e93bac
--- /dev/null
+++ b/src/rpc/auxpow_miner.cpp
@@ -0,0 +1,165 @@
+// Copyright (c) 2018 Daniel Kraft
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <rpc/auxpow_miner.h>
+
+#include <arith_uint256.h>
+#include <auxpow.h>
+#include <chainparams.h>
+#include <net.h>
+#include <rpc/protocol.h>
+#include <utilstrencodings.h>
+#include <utiltime.h>
+#include <validation.h>
+
+#include <cassert>
+
+namespace
+{
+
+void auxMiningCheck()
+{
+  if (!g_connman)
+    throw JSONRPCError (RPC_CLIENT_P2P_DISABLED,
+                        "Error: Peer-to-peer functionality missing or"
+                        " disabled");
+
+  if (g_connman->GetNodeCount (CConnman::CONNECTIONS_ALL) == 0
+        && !Params ().MineBlocksOnDemand ())
+    throw JSONRPCError (RPC_CLIENT_NOT_CONNECTED,
+                        "Dogecoin is not connected!");
+
+  if (IsInitialBlockDownload () && !Params ().MineBlocksOnDemand ())
+    throw JSONRPCError (RPC_CLIENT_IN_INITIAL_DOWNLOAD,
+                        "Dogecoin is downloading blocks...");
+
+  /* This should never fail, since the chain is already
+     past the point of merge-mining start.  Check nevertheless.  */
+  {
+    LOCK (cs_main);
+    const auto auxpowStart = Params ().GetConsensus ().nAuxpowStartHeight;
+    if (chainActive.Height () + 1 < auxpowStart)
+      throw std::runtime_error ("mining auxblock method is not yet available");
+  }
+}
+
+}  // anonymous namespace
+
+const CBlock*
+AuxpowMiner::getCurrentBlock (const CScript& scriptPubKey, uint256& target)
+{
+  AssertLockHeld (cs);
+
+  {
+    LOCK (cs_main);
+    if (pindexPrev != chainActive.Tip ()
+        || (mempool.GetTransactionsUpdated () != txUpdatedLast
+            && GetTime () - startTime > 60))
+      {
+        if (pindexPrev != chainActive.Tip ())
+          {
+            /* Clear old blocks since they're obsolete now.  */
+            blocks.clear ();
+            templates.clear ();
+            pblockCur = nullptr;
+          }
+
+        /* Create new block with nonce = 0 and extraNonce = 1.  */
+        std::unique_ptr<CBlockTemplate> newBlock
+            = BlockAssembler (Params ()).CreateNewBlock (scriptPubKey);
+        if (newBlock == nullptr)
+          throw JSONRPCError (RPC_OUT_OF_MEMORY, "out of memory");
+
+        /* Update state only when CreateNewBlock succeeded.  */
+        txUpdatedLast = mempool.GetTransactionsUpdated ();
+        pindexPrev = chainActive.Tip ();
+        startTime = GetTime ();
+
+        /* Finalise it by setting the version and building the merkle root.  */
+        IncrementExtraNonce (&newBlock->block, pindexPrev, extraNonce);
+        newBlock->block.SetAuxpowFlag (true);
+
+        /* Save in our map of constructed blocks.  */
+        pblockCur = &newBlock->block;
+        blocks[pblockCur->GetHash ()] = pblockCur;
+        templates.push_back (std::move (newBlock));
+      }
+  }
+
+  /* At this point, pblockCur is always initialised:  If we make it here
+     without creating a new block above, it means that, in particular,
+     pindexPrev == chainActive.Tip().  But for that to happen, we must
+     already have created a pblockCur in a previous call, as pindexPrev is
+     initialised only when pblockCur is.  */
+  assert (pblockCur);
+
+  arith_uint256 arithTarget;
+  bool fNegative, fOverflow;
+  arithTarget.SetCompact (pblockCur->nBits, &fNegative, &fOverflow);
+  if (fNegative || fOverflow || arithTarget == 0)
+    throw std::runtime_error ("invalid difficulty bits in block");
+  target = ArithToUint256 (arithTarget);
+
+  return pblockCur;
+}
+
+const CBlock*
+AuxpowMiner::lookupSavedBlock (const std::string& hashHex) const
+{
+  AssertLockHeld (cs);
+
+  uint256 hash;
+  hash.SetHex (hashHex);
+
+  const auto iter = blocks.find (hash);
+  if (iter == blocks.end ())
+    throw JSONRPCError (RPC_INVALID_PARAMETER, "block hash unknown");
+
+  return iter->second;
+}
+
+UniValue
+AuxpowMiner::createAuxBlock (const CScript& scriptPubKey)
+{
+  auxMiningCheck ();
+  LOCK (cs);
+
+  uint256 target;
+  const CBlock* pblock = getCurrentBlock (scriptPubKey, target);
+
+  UniValue result(UniValue::VOBJ);
+  result.pushKV ("hash", pblock->GetHash ().GetHex ());
+  result.pushKV ("chainid", pblock->GetChainId ());
+  result.pushKV ("previousblockhash", pblock->hashPrevBlock.GetHex ());
+  result.pushKV ("coinbasevalue",
+                 static_cast<int64_t> (pblock->vtx[0]->vout[0].nValue));
+  result.pushKV ("bits", strprintf ("%08x", pblock->nBits));
+  result.pushKV ("height", static_cast<int64_t> (pindexPrev->nHeight + 1));
+  result.pushKV ("target", HexStr (BEGIN (target), END (target)));
+
+  return result;
+}
+
+bool
+AuxpowMiner::submitAuxBlock (const std::string& hashHex,
+                             const std::string& auxpowHex) const
+{
+  auxMiningCheck ();
+
+  std::shared_ptr<CBlock> shared_block;
+  {
+    LOCK (cs);
+    const CBlock* pblock = lookupSavedBlock (hashHex);
+    shared_block = std::make_shared<CBlock> (*pblock);
+  }
+
+  const std::vector<unsigned char> vchAuxPow = ParseHex (auxpowHex);
+  CDataStream ss(vchAuxPow, SER_GETHASH, PROTOCOL_VERSION);
+  std::unique_ptr<CAuxPow> pow(new CAuxPow ());
+  ss >> *pow;
+  shared_block->SetAuxpow (std::move (pow));
+  assert (shared_block->GetHash ().GetHex () == hashHex);
+
+  return ProcessNewBlock (Params (), shared_block, true, nullptr);
+}
diff --git a/src/rpc/auxpow_miner.h b/src/rpc/auxpow_miner.h
new file mode 100644
index 000000000..159495730
--- /dev/null
+++ b/src/rpc/auxpow_miner.h
@@ -0,0 +1,95 @@
+// Copyright (c) 2018 Daniel Kraft
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_RPC_AUXPOW_MINER_H
+#define BITCOIN_RPC_AUXPOW_MINER_H
+
+#include <miner.h>
+#include <script/script.h>
+#include <sync.h>
+#include <uint256.h>
+#include <univalue.h>
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace auxpow_tests
+{
+class AuxpowMinerForTest;
+}
+
+/**
+ * This class holds "global" state used to construct blocks for the auxpow
+ * mining RPCs and the map of already constructed blocks to look them up
+ * in the submitauxblock RPC.
+ *
+ * It is used as a singleton that is initialised during startup, taking the
+ * place of the previously real global and static variables.
+ */
+class AuxpowMiner
+{
+
+private:
+
+  /** The lock used for state in this object.  */
+  mutable CCriticalSection cs;
+  /** All currently "active" block templates.  */
+  std::vector<std::unique_ptr<CBlockTemplate>> templates;
+  /** Maps block hashes to pointers in vTemplates.  Does not own the memory.  */
+  std::map<uint256, const CBlock*> blocks;
+
+  /**
+   * The block we are "currently" working on.  This does not own the memory,
+   * instead, it points into an element of templates.
+   */
+  CBlock* pblockCur = nullptr;
+  /** The current extra nonce for block creation.  */
+  unsigned extraNonce = 0;
+
+  /* Some data about when the current block (pblock) was constructed.  */
+  unsigned txUpdatedLast;
+  const CBlockIndex* pindexPrev = nullptr;
+  uint64_t startTime;
+
+  /**
+   * Constructs a new current block if necessary (checking the current state to
+   * see if "enough changed" for this), and returns a pointer to the block
+   * that should be returned to a miner for working on at the moment.  Also
+   * fills in the difficulty target value.
+   */
+  const CBlock* getCurrentBlock (const CScript& scriptPubKey, uint256& target);
+
+  /**
+   * Looks up a previously constructed block by its (hex-encoded) hash.  If the
+   * block is found, it is returned.  Otherwise, a JSONRPCError is thrown.
+   */
+  const CBlock* lookupSavedBlock (const std::string& hashHex) const;
+
+  friend class auxpow_tests::AuxpowMinerForTest;
+
+public:
+
+  AuxpowMiner () = default;
+
+  /**
+   * Performs the main work for the "createauxblock" RPC:  Construct a new block
+   * to work on with the given address for the block reward and return the
+   * necessary information for the miner to construct an auxpow for it.
+   */
+  UniValue createAuxBlock (const CScript& scriptPubKey);
+
+  /**
+   * Performs the main work for the "submitauxblock" RPC:  Look up the block
+   * previously created for the given hash, attach the given auxpow to it
+   * and try to submit it.  Returns true if all was successful and the block
+   * was accepted.
+   */
+  bool submitAuxBlock (const std::string& hashHex,
+                       const std::string& auxpowHex) const;
+
+};
+
+#endif // BITCOIN_RPC_AUXPOW_MINER_H
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 948553d9a..3309a9701 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -80,6 +80,42 @@ double GetDifficulty(const CBlockIndex* blockindex)
     return dDiff;
 }
 
+UniValue AuxpowToJSON(const CAuxPow& auxpow)
+{
+    UniValue result(UniValue::VOBJ);
+
+    {
+        UniValue tx(UniValue::VOBJ);
+        tx.pushKV("hex", EncodeHexTx(*auxpow.coinbaseTx.tx));
+        TxToUniv(*auxpow.coinbaseTx.tx, auxpow.parentBlock.GetHash(), tx);
+        result.pushKV("tx", tx);
+    }
+
+    result.pushKV("index", auxpow.coinbaseTx.nIndex);
+    result.pushKV("chainindex", auxpow.nChainIndex);
+
+    {
+        UniValue branch(UniValue::VARR);
+        for (const auto& node : auxpow.coinbaseTx.vMerkleBranch)
+            branch.push_back(node.GetHex());
+        result.pushKV("merklebranch", branch);
+    }
+
+    {
+        UniValue branch(UniValue::VARR);
+        for (const auto& node : auxpow.vChainMerkleBranch)
+            branch.push_back(node.GetHex());
+        result.pushKV("chainmerklebranch", branch);
+    }
+
+    CDataStream ssParent(SER_NETWORK, PROTOCOL_VERSION);
+    ssParent << auxpow.parentBlock;
+    const std::string strHex = HexStr(ssParent.begin(), ssParent.end());
+    result.pushKV("parentblock", strHex);
+
+    return result;
+}
+
 UniValue blockheaderToJSON(const CBlockIndex* blockindex)
 {
     AssertLockHeld(cs_main);
@@ -148,6 +184,9 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool tx
     result.pushKV("chainwork", blockindex->nChainWork.GetHex());
     result.pushKV("nTx", (uint64_t)blockindex->nTx);
 
+    if (block.auxpow)
+        result.pushKV("auxpow", AuxpowToJSON(*block.auxpow));
+
     if (blockindex->pprev)
         result.pushKV("previousblockhash", blockindex->pprev->GetBlockHash().GetHex());
     CBlockIndex *pnext = chainActive.Next(blockindex);
@@ -729,7 +768,7 @@ static UniValue getblockheader(const JSONRPCRequest& request)
     if (!fVerbose)
     {
         CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION);
-        ssBlock << pblockindex->GetBlockHeader();
+        ssBlock << pblockindex->GetBlockHeader(Params().GetConsensus());
         std::string strHex = HexStr(ssBlock.begin(), ssBlock.end());
         return strHex;
     }
@@ -1270,7 +1309,7 @@ UniValue getblockchaininfo(const JSONRPCRequest& request)
     softforks.push_back(SoftForkDesc("bip34", 2, tip, consensusParams));
     softforks.push_back(SoftForkDesc("bip66", 3, tip, consensusParams));
     softforks.push_back(SoftForkDesc("bip65", 4, tip, consensusParams));
-    for (int pos = Consensus::DEPLOYMENT_CSV; pos != Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++pos) {
+    for (int pos = Consensus::DEPLOYMENT_TESTDUMMY + 1; pos != Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++pos) {
         BIP9SoftForkDescPushBack(bip9_softforks, consensusParams, static_cast<Consensus::DeploymentPos>(pos));
     }
     obj.pushKV("softforks",             softforks);
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 0622e3b72..75c71a323 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -16,6 +16,7 @@
 #include <net.h>
 #include <policy/fees.h>
 #include <pow.h>
+#include <rpc/auxpow_miner.h>
 #include <rpc/blockchain.h>
 #include <rpc/mining.h>
 #include <rpc/server.h>
@@ -26,8 +27,9 @@
 #include <validationinterface.h>
 #include <warnings.h>
 
-#include <memory>
 #include <stdint.h>
+#include <string>
+#include <utility>
 
 unsigned int ParseConfirmTarget(const UniValue& value)
 {
@@ -126,14 +128,15 @@ UniValue generateBlocks(std::shared_ptr<CReserveScript> coinbaseScript, int nGen
             LOCK(cs_main);
             IncrementExtraNonce(pblock, chainActive.Tip(), nExtraNonce);
         }
-        while (nMaxTries > 0 && pblock->nNonce < nInnerLoopCount && !CheckProofOfWork(pblock->GetPoWHash(), pblock->nBits, Params().GetConsensus())) {
-            ++pblock->nNonce;
+        auto& miningHeader = CAuxPow::initAuxPow(*pblock);
+        while (nMaxTries > 0 && miningHeader.nNonce < nInnerLoopCount && !CheckProofOfWork(miningHeader.GetHash(), pblock->nBits, Params().GetConsensus())) {
+            ++miningHeader.nNonce;
             --nMaxTries;
         }
         if (nMaxTries == 0) {
             break;
         }
-        if (pblock->nNonce == nInnerLoopCount) {
+        if (miningHeader.nNonce == nInnerLoopCount) {
             continue;
         }
         std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(*pblock);
@@ -489,11 +492,10 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
         // TODO: Maybe recheck connections/IBD and (if something wrong) send an expires-immediately template to stop miners?
     }
 
-    const struct VBDeploymentInfo& segwit_info = VersionBitsDeploymentInfo[Consensus::DEPLOYMENT_SEGWIT];
     // If the caller is indicating segwit support, then allow CreateNewBlock()
     // to select witness transactions, after segwit activates (otherwise
     // don't).
-    bool fSupportsSegwit = setClientRules.find(segwit_info.name) != setClientRules.end();
+    bool fSupportsSegwit = setClientRules.find("segwit") != setClientRules.end();
 
     // Update block
     static CBlockIndex* pindexPrev;
@@ -533,7 +535,7 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
     pblock->nNonce = 0;
 
     // NOTE: If at some point we support pre-segwit miners post-segwit-activation, this needs to take segwit support into consideration
-    const bool fPreSegWit = (ThresholdState::ACTIVE != VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_SEGWIT, versionbitscache));
+    const bool fPreSegWit = !IsWitnessEnabled(pindexPrev, consensusParams);
 
     UniValue aCaps(UniValue::VARR); aCaps.push_back("proposal");
 
@@ -932,6 +934,68 @@ static UniValue estimaterawfee(const JSONRPCRequest& request)
     return result;
 }
 
+/* ************************************************************************** */
+/* Merge mining.  */
+
+std::unique_ptr<AuxpowMiner> g_auxpow_miner;
+
+UniValue createauxblock(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 1)
+        throw std::runtime_error(
+            "createauxblock <address>\n"
+            "\ncreate a new block and return information required to merge-mine it.\n"
+            "\nArguments:\n"
+            "1. address      (string, required) specify coinbase transaction payout address\n"
+            "\nResult:\n"
+            "{\n"
+            "  \"hash\"               (string) hash of the created block\n"
+            "  \"chainid\"            (numeric) chain ID for this block\n"
+            "  \"previousblockhash\"  (string) hash of the previous block\n"
+            "  \"coinbasevalue\"      (numeric) value of the block's coinbase\n"
+            "  \"bits\"               (string) compressed target of the block\n"
+            "  \"height\"             (numeric) height of the block\n"
+            "  \"target\"             (string) target in reversed byte order\n"
+            "}\n"
+            "\nExamples:\n"
+            + HelpExampleCli("createauxblock", "\"address\"")
+            + HelpExampleRpc("createauxblock", "\"address\"")
+            );
+
+    // Check coinbase payout address
+    const CTxDestination coinbaseScript
+      = DecodeDestination(request.params[0].get_str());
+    if (!IsValidDestination(coinbaseScript)) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
+                           "Error: Invalid coinbase payout address");
+    }
+    const CScript scriptPubKey = GetScriptForDestination(coinbaseScript);
+
+    return g_auxpow_miner->createAuxBlock(scriptPubKey);
+}
+
+UniValue submitauxblock(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 2)
+        throw std::runtime_error(
+            "submitauxblock <hash> <auxpow>\n"
+            "\nsubmit a solved auxpow for a previously block created by 'createauxblock'.\n"
+            "\nArguments:\n"
+            "1. hash      (string, required) hash of the block to submit\n"
+            "2. auxpow    (string, required) serialised auxpow found\n"
+            "\nResult:\n"
+            "xxxxx        (boolean) whether the submitted block was correct\n"
+            "\nExamples:\n"
+            + HelpExampleCli("submitauxblock", "\"hash\" \"serialised auxpow\"")
+            + HelpExampleRpc("submitauxblock", "\"hash\" \"serialised auxpow\"")
+            );
+
+    return g_auxpow_miner->submitAuxBlock(request.params[0].get_str(),
+                                          request.params[1].get_str());
+}
+
+/* ************************************************************************** */
+
 static const CRPCCommand commands[] =
 { //  category              name                      actor (function)         argNames
   //  --------------------- ------------------------  -----------------------  ----------
@@ -940,7 +1004,8 @@ static const CRPCCommand commands[] =
     { "mining",             "prioritisetransaction",  &prioritisetransaction,  {"txid","dummy","fee_delta"} },
     { "mining",             "getblocktemplate",       &getblocktemplate,       {"template_request"} },
     { "mining",             "submitblock",            &submitblock,            {"hexdata","dummy"} },
-
+    { "mining",             "createauxblock",         &createauxblock,         {"address"} },
+    { "mining",             "submitauxblock",         &submitauxblock,         {"hash", "auxpow"} },
 
     { "generating",         "generatetoaddress",      &generatetoaddress,      {"nblocks","address","maxtries"} },
 
diff --git a/src/rpc/mining.h b/src/rpc/mining.h
index 8d4627315..759d35e64 100644
--- a/src/rpc/mining.h
+++ b/src/rpc/mining.h
@@ -9,10 +9,17 @@
 
 #include <univalue.h>
 
+#include <memory>
+
+class AuxpowMiner;
+
 /** Generate blocks (mine) */
 UniValue generateBlocks(std::shared_ptr<CReserveScript> coinbaseScript, int nGenerate, uint64_t nMaxTries, bool keepScript);
 
 /** Check bounds on a command line confirm target */
 unsigned int ParseConfirmTarget(const UniValue& value);
 
+/** Singleton instance of the AuxpowMiner, created during startup.  */
+extern std::unique_ptr<AuxpowMiner> g_auxpow_miner;
+
 #endif
diff --git a/src/test/auxpow_tests.cpp b/src/test/auxpow_tests.cpp
new file mode 100644
index 000000000..6447ef9fd
--- /dev/null
+++ b/src/test/auxpow_tests.cpp
@@ -0,0 +1,591 @@
+// Copyright (c) 2014-2018 Daniel Kraft
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <arith_uint256.h>
+#include <auxpow.h>
+#include <chainparams.h>
+#include <coins.h>
+#include <consensus/merkle.h>
+#include <dogecoin.h>
+#include <validation.h>
+#include <pow.h>
+#include <primitives/block.h>
+#include <rpc/auxpow_miner.h>
+#include <script/script.h>
+#include <utilstrencodings.h>
+#include <utiltime.h>
+#include <uint256.h>
+#include <univalue.h>
+
+#include <test/test_bitcoin.h>
+
+#include <boost/test/unit_test.hpp>
+
+#include <algorithm>
+#include <vector>
+
+/* No space between BOOST_AUTO_TEST_SUITE and '(', so that extraction of
+   the test-suite name works with grep as done in the Makefile.  */
+BOOST_AUTO_TEST_SUITE(auxpow_tests)
+
+/* ************************************************************************** */
+
+/**
+ * Tamper with a uint256 (modify it).
+ * @param num The number to modify.
+ */
+static void
+tamperWith(uint256& num)
+{
+    arith_uint256 modifiable = UintToArith256(num);
+    modifiable += 1;
+    num = ArithToUint256(modifiable);
+}
+
+/**
+ * Helper class that is friend to CAuxPow and makes the internals accessible
+ * to the test code.
+ */
+class CAuxPowForTest : public CAuxPow
+{
+
+public:
+
+  explicit inline CAuxPowForTest (CTransactionRef txIn)
+    : CAuxPow (txIn)
+  {}
+
+  using CAuxPow::coinbaseTx;
+  using CAuxPow::vChainMerkleBranch;
+  using CAuxPow::nChainIndex;
+  using CAuxPow::parentBlock;
+
+  using CAuxPow::CheckMerkleBranch;
+
+};
+
+/**
+ * Utility class to construct auxpow's and manipulate them.  This is used
+ * to simulate various scenarios.
+ */
+class CAuxpowBuilder
+{
+public:
+
+    /** The parent block (with coinbase, not just header).  */
+    CBlock parentBlock;
+
+    /** The auxpow's merkle branch (connecting it to the coinbase).  */
+    std::vector<uint256> auxpowChainMerkleBranch;
+    /** The auxpow's merkle tree index.  */
+    int auxpowChainIndex;
+
+    /**
+   * Initialise everything.
+   * @param baseVersion The parent block's base version to use.
+   * @param chainId The parent block's chain ID to use.
+   */
+    CAuxpowBuilder(int baseVersion, int chainId);
+
+    /**
+   * Set the coinbase's script.
+   * @param scr Set it to this script.
+   */
+    void setCoinbase(const CScript& scr);
+
+    /**
+   * Build the auxpow merkle branch.  The member variables will be
+   * set accordingly.  This has to be done before constructing the coinbase
+   * itself (which must contain the root merkle hash).  When we have the
+   * coinbase afterwards, the member variables can be used to initialise
+   * the CAuxPow object from it.
+   * @param hashAux The merge-mined chain's block hash.
+   * @param h Height of the merkle tree to build.
+   * @param index Index to use in the merkle tree.
+   * @return The root hash, with reversed endian.
+   */
+    std::vector<unsigned char> buildAuxpowChain(const uint256& hashAux, unsigned h, int index);
+
+    /**
+   * Build the finished CAuxPow object.  We assume that the auxpowChain
+   * member variables are already set.  We use the passed in transaction
+   * as the base.  It should (probably) be the parent block's coinbase.
+   * @param tx The base tx to use.
+   * @return The constructed CAuxPow object.
+   */
+    CAuxPow get(const CTransactionRef tx) const;
+
+    /**
+   * Build the finished CAuxPow object from the parent block's coinbase.
+   * @return The constructed CAuxPow object.
+   */
+    inline CAuxPow
+    get() const
+    {
+        assert(!parentBlock.vtx.empty());
+        return get(parentBlock.vtx[0]);
+    }
+
+    /**
+   * Returns the finished CAuxPow object and returns it as std::unique_ptr.
+   */
+  inline std::unique_ptr<CAuxPow>
+  getUnique () const
+  {
+    return std::unique_ptr<CAuxPow>(new CAuxPow (get ()));
+  }
+
+  /**
+   * Build a data vector to be included in the coinbase.  It consists
+   * of the aux hash, the merkle tree size and the nonce.  Optionally,
+   * the header can be added as well.
+   * @param header Add the header?
+   * @param hashAux The aux merkle root hash.
+   * @param h Height of the merkle tree.
+   * @param nonce The nonce value to use.
+   * @return The constructed data.
+   */
+  static std::vector<unsigned char> buildCoinbaseData (bool header, const std::vector<unsigned char>& auxRoot,
+                                    unsigned h, int nonce);
+
+};
+
+CAuxpowBuilder::CAuxpowBuilder(int baseVersion, int chainId)
+    : auxpowChainIndex(-1)
+{
+    parentBlock.SetBaseVersion(baseVersion, chainId);
+}
+
+void
+CAuxpowBuilder::setCoinbase (const CScript& scr)
+{
+    CMutableTransaction mtx;
+    mtx.vin.resize(1);
+    mtx.vin[0].prevout.SetNull();
+    mtx.vin[0].scriptSig = scr;
+
+    parentBlock.vtx.clear();
+    parentBlock.vtx.push_back(MakeTransactionRef(std::move(mtx)));
+    parentBlock.hashMerkleRoot = BlockMerkleRoot(parentBlock);
+}
+
+std::vector<unsigned char>
+CAuxpowBuilder::buildAuxpowChain(const uint256& hashAux, unsigned h, int index)
+{
+    auxpowChainIndex = index;
+
+    /* Just use "something" for the branch.  Doesn't really matter.  */
+    auxpowChainMerkleBranch.clear();
+    for (unsigned i = 0; i < h; ++i)
+        auxpowChainMerkleBranch.push_back(ArithToUint256(arith_uint256(i)));
+
+  const uint256 hash
+    = CAuxPowForTest::CheckMerkleBranch (hashAux, auxpowChainMerkleBranch,
+                                         index);
+
+    std::vector<unsigned char> res = ToByteVector(hash);
+    std::reverse(res.begin(), res.end());
+
+    return res;
+}
+
+CAuxPow
+CAuxpowBuilder::get(const CTransactionRef tx) const
+{
+    LOCK(cs_main);
+
+  CAuxPowForTest res(tx);
+  res.coinbaseTx.hashBlock = parentBlock.GetHash ();
+  res.coinbaseTx.nIndex = 0;
+  res.coinbaseTx.vMerkleBranch
+      = merkle_tests::BlockMerkleBranch (parentBlock, res.coinbaseTx.nIndex);
+
+    res.vChainMerkleBranch = auxpowChainMerkleBranch;
+    res.nChainIndex = auxpowChainIndex;
+    res.parentBlock = parentBlock;
+
+    return res;
+}
+
+std::vector<unsigned char>
+CAuxpowBuilder::buildCoinbaseData (bool header, const std::vector<unsigned char>& auxRoot,
+                                   unsigned h, int nonce)
+{
+    std::vector<unsigned char> res;
+
+    if (header)
+        res.insert(res.end(), UBEGIN(pchMergedMiningHeader),
+            UEND(pchMergedMiningHeader));
+    res.insert(res.end(), auxRoot.begin(), auxRoot.end());
+
+    const int size = (1 << h);
+    res.insert(res.end(), UBEGIN(size), UEND(size));
+    res.insert(res.end(), UBEGIN(nonce), UEND(nonce));
+
+    return res;
+}
+
+/* ************************************************************************** */
+
+BOOST_FIXTURE_TEST_CASE (check_auxpow, BasicTestingSetup)
+{
+    const Consensus::Params& params = Params().GetConsensus();
+    CAuxpowBuilder builder(5, 42);
+    CAuxPow auxpow;
+
+    const uint256 hashAux = ArithToUint256(arith_uint256(12345));
+    const int32_t ourChainId = params.nAuxpowChainId;
+    const unsigned height = 30;
+    const int nonce = 7;
+    int index;
+
+    std::vector<unsigned char> auxRoot, data;
+    CScript scr;
+
+    /* Build a correct auxpow.  The height is the maximally allowed one.  */
+    index = CAuxPow::getExpectedIndex(nonce, ourChainId, height);
+    auxRoot = builder.buildAuxpowChain(hashAux, height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    scr = (CScript() << 2809 << 2013) + COINBASE_FLAGS;
+    scr = (scr << OP_2 << data);
+    builder.setCoinbase(scr);
+    BOOST_CHECK(builder.get().check(hashAux, ourChainId, params));
+
+    /* Check that the auxpow is invalid if we change either the aux block's
+     hash or the chain ID.  */
+    uint256 modifiedAux(hashAux);
+    tamperWith(modifiedAux);
+    BOOST_CHECK(!builder.get().check(modifiedAux, ourChainId, params));
+    BOOST_CHECK(!builder.get().check(hashAux, ourChainId + 1, params));
+
+    /* Non-coinbase parent tx should fail.  Note that we can't just copy
+     the coinbase literally, as we have to get a tx with different hash.  */
+    const CTransactionRef oldCoinbase = builder.parentBlock.vtx[0];
+    builder.setCoinbase(scr << 5);
+    builder.parentBlock.vtx.push_back(oldCoinbase);
+    builder.parentBlock.hashMerkleRoot = BlockMerkleRoot(builder.parentBlock);
+    auxpow = builder.get(builder.parentBlock.vtx[0]);
+    BOOST_CHECK(auxpow.check(hashAux, ourChainId, params));
+    auxpow = builder.get(builder.parentBlock.vtx[1]);
+    BOOST_CHECK(!auxpow.check(hashAux, ourChainId, params));
+
+    /* The parent chain can't have the same chain ID.  */
+    CAuxpowBuilder builder2(builder);
+    builder2.parentBlock.SetChainId(100);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+    builder2.parentBlock.SetChainId(ourChainId);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    /* Disallow too long merkle branches.  */
+    builder2 = builder;
+    index = CAuxPow::getExpectedIndex(nonce, ourChainId, height + 1);
+    auxRoot = builder2.buildAuxpowChain(hashAux, height + 1, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height + 1, nonce);
+    scr = (CScript() << 2809 << 2013) + COINBASE_FLAGS;
+    scr = (scr << OP_2 << data);
+    builder2.setCoinbase(scr);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    /* Verify that we compare correctly to the parent block's merkle root.  */
+    builder2 = builder;
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+    tamperWith(builder2.parentBlock.hashMerkleRoot);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    /* Build a non-header legacy version and check that it is also accepted.  */
+    builder2 = builder;
+    index = CAuxPow::getExpectedIndex(nonce, ourChainId, height);
+    auxRoot = builder2.buildAuxpowChain(hashAux, height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(false, auxRoot, height, nonce);
+    scr = (CScript() << 2809 << 2013) + COINBASE_FLAGS;
+    scr = (scr << OP_2 << data);
+    builder2.setCoinbase(scr);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+
+    /* However, various attempts at smuggling two roots in should be detected.  */
+
+  const std::vector<unsigned char> wrongAuxRoot
+    = builder2.buildAuxpowChain (modifiedAux, height, index);
+  std::vector<unsigned char> data2
+    = CAuxpowBuilder::buildCoinbaseData (false, wrongAuxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data << data2);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+    builder2.setCoinbase(CScript() << data2 << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    data2 = CAuxpowBuilder::buildCoinbaseData(true, wrongAuxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data << data2);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+    builder2.setCoinbase(CScript() << data2 << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data << data2);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+    builder2.setCoinbase(CScript() << data2 << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    data2 = CAuxpowBuilder::buildCoinbaseData(false, wrongAuxRoot,
+        height, nonce);
+    builder2.setCoinbase(CScript() << data << data2);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+    builder2.setCoinbase(CScript() << data2 << data);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+
+    /* Verify that the appended nonce/size values are checked correctly.  */
+
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+
+    data.pop_back();
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height - 1, nonce);
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce + 3);
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    /* Put the aux hash in an invalid merkle tree position.  */
+
+    auxRoot = builder.buildAuxpowChain(hashAux, height, index + 1);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(!builder2.get().check(hashAux, ourChainId, params));
+
+    auxRoot = builder.buildAuxpowChain(hashAux, height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder2.setCoinbase(CScript() << data);
+    BOOST_CHECK(builder2.get().check(hashAux, ourChainId, params));
+}
+
+/* ************************************************************************** */
+
+/**
+ * Mine a block (assuming minimal difficulty) that either matches
+ * or doesn't match the difficulty target specified in the block header.
+ * @param block The block to mine (by updating nonce).
+ * @param ok Whether the block should be ok for PoW.
+ * @param nBits Use this as difficulty if specified.
+ */
+static void
+mineBlock(CBlockHeader& block, bool ok, int nBits = -1)
+{
+    if (nBits == -1)
+        nBits = block.nBits;
+
+    arith_uint256 target;
+    target.SetCompact(nBits);
+
+    block.nNonce = 0;
+  while (true)
+    {
+        const bool nowOk = (UintToArith256(block.GetHash()) <= target);
+        if ((ok && nowOk) || (!ok && !nowOk))
+            break;
+
+        ++block.nNonce;
+    }
+
+    if (ok)
+        BOOST_CHECK(CheckProofOfWork(block.GetHash(), nBits, Params().GetConsensus()));
+    else
+        BOOST_CHECK(!CheckProofOfWork(block.GetHash(), nBits, Params().GetConsensus()));
+}
+
+BOOST_FIXTURE_TEST_CASE (auxpow_pow, BasicTestingSetup)
+{
+    /* Use regtest parameters to allow mining with easy difficulty.  */
+    SelectParams(CBaseChainParams::REGTEST);
+    const Consensus::Params& params = Params().GetConsensus();
+
+    const arith_uint256 target = (~arith_uint256(0) >> 1);
+    CBlockHeader block;
+    block.nBits = target.GetCompact();
+
+    /* Verify the block version checks.  */
+
+    block.nVersion = 1;
+    mineBlock(block, true);
+    BOOST_CHECK(CheckAuxPowProofOfWork(block, params));
+
+    // Dogecoin block version 2 can be both AuxPoW and regular, so test 3
+
+    block.nVersion = 3;
+    mineBlock(block, true);
+    BOOST_CHECK(!CheckAuxPowProofOfWork(block, params));
+
+    block.SetBaseVersion(2, params.nAuxpowChainId);
+    mineBlock(block, true);
+    BOOST_CHECK(CheckAuxPowProofOfWork(block, params));
+
+    block.SetChainId(params.nAuxpowChainId + 1);
+    mineBlock(block, true);
+    BOOST_CHECK(!CheckAuxPowProofOfWork(block, params));
+
+    /* Check the case when the block does not have auxpow (this is true
+     right now).  */
+
+    block.SetChainId(params.nAuxpowChainId);
+    block.SetAuxpowFlag(true);
+    mineBlock(block, true);
+    BOOST_CHECK(!CheckAuxPowProofOfWork(block, params));
+
+    block.SetAuxpowFlag(false);
+    mineBlock(block, true);
+    BOOST_CHECK(CheckAuxPowProofOfWork(block, params));
+    mineBlock(block, false);
+    BOOST_CHECK(!CheckAuxPowProofOfWork(block, params));
+
+    /* ****************************************** */
+    /* Check the case that the block has auxpow.  */
+
+    CAuxpowBuilder builder(5, 42);
+    CAuxPow auxpow;
+    const int32_t ourChainId = params.nAuxpowChainId;
+    const unsigned height = 3;
+    const int nonce = 7;
+    const int index = CAuxPow::getExpectedIndex(nonce, ourChainId, height);
+    std::vector<unsigned char> auxRoot, data;
+
+    /* Valid auxpow, PoW check of parent block.  */
+    block.SetAuxpowFlag(true);
+    auxRoot = builder.buildAuxpowChain(block.GetHash(), height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder.setCoinbase(CScript() << data);
+    mineBlock(builder.parentBlock, false, block.nBits);
+    block.SetAuxpow (builder.getUnique ());
+    BOOST_CHECK (!CheckAuxPowProofOfWork (block, params));
+    mineBlock(builder.parentBlock, true, block.nBits);
+    block.SetAuxpow (builder.getUnique ());
+    BOOST_CHECK (CheckAuxPowProofOfWork (block, params));
+
+    /* Mismatch between auxpow being present and block.nVersion.  Note that
+     block.SetAuxpow sets also the version and that we want to ensure
+     that the block hash itself doesn't change due to version changes.
+     This requires some work arounds.  */
+    block.SetAuxpowFlag(false);
+    const uint256 hashAux = block.GetHash();
+    auxRoot = builder.buildAuxpowChain(hashAux, height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder.setCoinbase(CScript() << data);
+    mineBlock(builder.parentBlock, true, block.nBits);
+  block.SetAuxpow (builder.getUnique ());
+    BOOST_CHECK(hashAux != block.GetHash());
+    block.SetAuxpowFlag(false);
+    BOOST_CHECK(hashAux == block.GetHash());
+    BOOST_CHECK(!CheckAuxPowProofOfWork(block, params));
+
+    /* Modifying the block invalidates the PoW.  */
+    block.SetAuxpowFlag(true);
+    auxRoot = builder.buildAuxpowChain(block.GetHash(), height, index);
+    data = CAuxpowBuilder::buildCoinbaseData(true, auxRoot, height, nonce);
+    builder.setCoinbase(CScript() << data);
+    mineBlock(builder.parentBlock, true, block.nBits);
+    block.SetAuxpow (builder.getUnique ());
+    BOOST_CHECK (CheckAuxPowProofOfWork (block, params));
+    tamperWith(block.hashMerkleRoot);
+    BOOST_CHECK (!CheckAuxPowProofOfWork (block, params));
+}
+
+/* ************************************************************************** */
+
+/**
+ * Helper class that is friend to AuxpowMiner and makes the tested methods
+ * accessible to the test code.
+ */
+class AuxpowMinerForTest : public AuxpowMiner
+{
+
+public:
+
+  using AuxpowMiner::cs;
+
+  using AuxpowMiner::getCurrentBlock;
+  using AuxpowMiner::lookupSavedBlock;
+
+};
+
+BOOST_FIXTURE_TEST_CASE (auxpow_miner_blockRegeneration, TestChain240Setup)
+{
+  AuxpowMinerForTest miner;
+  LOCK (miner.cs);
+
+  /* We use mocktime so that we can control GetTime() as it is used in the
+     logic that determines whether or not to reconstruct a block.  The "base"
+     time is set such that the blocks we have from the fixture are fresh.  */
+  const int64_t baseTime = chainActive.Tip ()->GetMedianTimePast () + 1;
+  SetMockTime (baseTime);
+
+  /* Construct a first block.  */
+  CScript scriptPubKey;
+  uint256 target;
+  const CBlock* pblock1 = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock1 != nullptr);
+  const uint256 hash1 = pblock1->GetHash ();
+
+  /* Verify target computation.  */
+  arith_uint256 expected;
+  expected.SetCompact (pblock1->nBits);
+  BOOST_CHECK (target == ArithToUint256 (expected));
+
+  /* Calling the method again should return the same, cached block a second
+     time (even if we advance the clock, since there are no new
+     transactions).  */
+  SetMockTime (baseTime + 240);
+  const CBlock* pblock = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock == pblock1 && pblock->GetHash () == hash1);
+
+  /* Mine a block, then we should get a new auxpow block constructed.  Note that
+     it can be the same *pointer* if the memory was reused after clearing it,
+     so we can only verify that the hash is different.  */
+  CreateAndProcessBlock ({}, scriptPubKey);
+  const CBlock* pblock2 = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock2 != nullptr);
+  const uint256 hash2 = pblock2->GetHash ();
+  BOOST_CHECK (hash2 != hash1);
+
+  /* Add a new transaction to the mempool.  */
+  TestMemPoolEntryHelper entry;
+  CMutableTransaction mtx;
+  mtx.vout.emplace_back (1234, scriptPubKey);
+  {
+    LOCK (mempool.cs);
+    mempool.addUnchecked (mtx.GetHash (), entry.FromTx (mtx));
+  }
+
+  /* We should still get back the cached block, for now.  */
+  SetMockTime (baseTime + 300);
+  pblock = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock == pblock2 && pblock->GetHash () == hash2);
+
+  /* With time advanced too far, we get a new block.  This time, we should also
+     definitely get a different pointer, as there is no clearing.  The old
+     blocks are freed only after a new tip is found.  */
+  SetMockTime (baseTime + 301);
+  const CBlock* pblock3 = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock3 != pblock2 && pblock3->GetHash () != hash2);
+}
+
+BOOST_FIXTURE_TEST_CASE (auxpow_miner_createAndLookupBlock, TestChain240Setup)
+{
+  AuxpowMinerForTest miner;
+  LOCK (miner.cs);
+
+  CScript scriptPubKey;
+  uint256 target;
+  const CBlock* pblock = miner.getCurrentBlock (scriptPubKey, target);
+  BOOST_CHECK (pblock != nullptr);
+
+  BOOST_CHECK (miner.lookupSavedBlock (pblock->GetHash ().GetHex ()) == pblock);
+  BOOST_CHECK_THROW (miner.lookupSavedBlock ("foobar"), UniValue);
+}
+
+/* ************************************************************************** */
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index 63b91b74c..0eb5b90da 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -21,15 +21,6 @@ void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, CTxUndo &txund
 
 namespace
 {
-//! equality test
-bool operator==(const Coin &a, const Coin &b) {
-    // Empty Coin objects are always equal.
-    if (a.IsSpent() && b.IsSpent()) return true;
-    return a.fCoinBase == b.fCoinBase &&
-           a.nHeight == b.nHeight &&
-           a.out == b.out;
-}
-
 class CCoinsViewTest : public CCoinsView
 {
     uint256 hashBestBlock_;
diff --git a/src/test/dogecoin_tests.cpp b/src/test/dogecoin_tests.cpp
index f1d60f709..b5d7716d5 100644
--- a/src/test/dogecoin_tests.cpp
+++ b/src/test/dogecoin_tests.cpp
@@ -83,7 +83,7 @@ BOOST_AUTO_TEST_CASE(subsidy_limit_test)
         CAmount nSubsidy = GetDogecoinBlockSubsidy(nHeight, params, prevHash);
         CAmount nExpectedSubsidy = (500000 >> (nHeight / 100000)) * COIN;
         BOOST_CHECK(MoneyRange(nSubsidy));
-        BOOST_CHECK(nSubsidy == nExpectedSubsidy);
+        BOOST_CHECK_EQUAL(nSubsidy, nExpectedSubsidy);
         nSum += nSubsidy * nStepSize;
     }
 
@@ -96,10 +96,99 @@ BOOST_AUTO_TEST_CASE(subsidy_limit_test)
 
     // Test reward at 600k+ is constant
     CAmount nConstantSubsidy = GetDogecoinBlockSubsidy(600000, params, prevHash);
-    BOOST_CHECK(nConstantSubsidy == 10000 * COIN);
+    BOOST_CHECK_EQUAL(nConstantSubsidy, 10000 * COIN);
 
     nConstantSubsidy = GetDogecoinBlockSubsidy(700000, params, prevHash);
-    BOOST_CHECK(nConstantSubsidy == 10000 * COIN);
+    BOOST_CHECK_EQUAL(nConstantSubsidy, 10000 * COIN);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_difficulty_limit)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1386474927; // Block # 1
+    
+    pindexLast.nHeight = 239;
+    pindexLast.nTime = 1386475638; // Block #239
+    pindexLast.nBits = 0x1e0ffff0;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1e00ffff);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_pre_digishield)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+    
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1386942008; // Block 9359
+
+    pindexLast.nHeight = 9599;
+    pindexLast.nTime = 1386954113;
+    pindexLast.nBits = 0x1c1a1206;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1c15ea59);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_digishield)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+    
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1395094427;
+
+    // First hard-fork at 145,000, which applies to block 145,001 onwards
+    pindexLast.nHeight = 145000;
+    pindexLast.nTime = 1395094679;
+    pindexLast.nBits = 0x1b499dfd;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1b671062);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_digishield_modulated_upper)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+    
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1395100835;
+
+    // Test the upper bound on modulated time using mainnet block #145,107
+    pindexLast.nHeight = 145107;
+    pindexLast.nTime = 1395101360;
+    pindexLast.nBits = 0x1b3439cd;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1b4e56b3);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_digishield_modulated_lower)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+    
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1395380517;
+
+    // Test the lower bound on modulated time using mainnet block #149,423
+    pindexLast.nHeight = 149423;
+    pindexLast.nTime = 1395380447;
+    pindexLast.nBits = 0x1b446f21;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1b335358);
+}
+
+BOOST_AUTO_TEST_CASE(get_next_work_digishield_rounding)
+{
+    SelectParams(CBaseChainParams::MAIN);
+    const Consensus::Params& params = Params().GetConsensus();
+    
+    CBlockIndex pindexLast;
+    int64_t nLastRetargetTime = 1395094679;
+
+    // Test case for correct rounding of modulated time - this depends on
+    // handling of integer division, and is not obvious from the code
+    pindexLast.nHeight = 145001;
+    pindexLast.nTime = 1395094727;
+    pindexLast.nBits = 0x1b671062;
+    BOOST_CHECK_EQUAL(CalculateDogecoinNextWorkRequired(&pindexLast, nLastRetargetTime, params), 0x1b6558a4);
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/merkle_tests.cpp b/src/test/merkle_tests.cpp
index 5e55ad662..5e88e8fee 100644
--- a/src/test/merkle_tests.cpp
+++ b/src/test/merkle_tests.cpp
@@ -116,7 +116,7 @@ static std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leav
     return ret;
 }
 
-static std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
+std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
 {
     std::vector<uint256> leaves;
     leaves.resize(block.vtx.size());
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index 4e88bd4c4..6dd0d8b22 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -197,3 +197,12 @@ CBlock getBlock13b8a()
     stream >> block;
     return block;
 }
+
+//! equality test
+bool operator==(const Coin &a, const Coin &b) {
+    // Empty Coin objects are always equal.
+    if (a.IsSpent() && b.IsSpent()) return true;
+    return a.fCoinBase == b.fCoinBase &&
+           a.nHeight == b.nHeight &&
+           a.out == b.out;
+}
diff --git a/src/test/test_bitcoin.h b/src/test/test_bitcoin.h
index 0643e6e04..82bf98da6 100644
--- a/src/test/test_bitcoin.h
+++ b/src/test/test_bitcoin.h
@@ -127,4 +127,12 @@ CBlock getBlock13b8a();
 // define an implicit conversion here so that uint256 may be used directly in BOOST_CHECK_*
 std::ostream& operator<<(std::ostream& os, const uint256& num);
 
+/* This is defined in merkle_tests.cpp, but also used by auxpow_tests.cpp.  */
+namespace merkle_tests {
+std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position);
+}
+
+// Define == for coin equality (used by multiple tests).
+bool operator==(const Coin &a, const Coin &b);
+
 #endif
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 998cf7264..2e9cc3d87 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -273,10 +273,11 @@ bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams,
                 pindexNew->nNonce         = diskindex.nNonce;
                 pindexNew->nStatus        = diskindex.nStatus;
                 pindexNew->nTx            = diskindex.nTx;
-                pindexNew->hashBlockPoW   = diskindex.hashBlockPoW;
 
-                if (!CheckProofOfWork(pindexNew->GetBlockPoWHash(), pindexNew->nBits, consensusParams))
-                    return error("%s: CheckProofOfWork failed: %s", __func__, pindexNew->ToString());
+                /* Bitcoin checks the PoW here.  We don't do this because
+                   the CDiskBlockIndex does not contain the auxpow.
+                   This check isn't important, since the data on disk should
+                   already be valid and can be trusted.  */
 
                 pcursor->Next();
             } else {
diff --git a/src/validation.cpp b/src/validation.cpp
index c14db2454..0086d3911 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -6,6 +6,7 @@
 #include <validation.h>
 
 #include <arith_uint256.h>
+#include <auxpow.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <checkpoints.h>
@@ -1074,7 +1075,11 @@ static bool WriteBlockToDisk(const CBlock& block, CDiskBlockPos& pos, const CMes
     return true;
 }
 
-bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus::Params& consensusParams)
+/* Generic implementation of block reading that can handle
+   both a block and its header.  */
+
+template<typename T>
+static bool ReadBlockOrHeader(T& block, const CDiskBlockPos& pos, const Consensus::Params& consensusParams)
 {
     block.SetNull();
 
@@ -1092,13 +1097,14 @@ bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus:
     }
 
     // Check the header
-    if (!CheckProofOfWork(block.GetPoWHash(), block.nBits, consensusParams))
+    if (!CheckAuxPowProofOfWork(block, consensusParams))
         return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
 
     return true;
 }
 
-bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
+template<typename T>
+static bool ReadBlockOrHeader(T& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
 {
     CDiskBlockPos blockPos;
     {
@@ -1106,7 +1112,7 @@ bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus
         blockPos = pindex->GetBlockPos();
     }
 
-    if (!ReadBlockFromDisk(block, blockPos, consensusParams))
+    if (!ReadBlockOrHeader(block, blockPos, consensusParams))
         return false;
     if (block.GetHash() != pindex->GetBlockHash())
         return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() doesn't match index for %s at %s",
@@ -1114,6 +1120,21 @@ bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus
     return true;
 }
 
+bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus::Params& consensusParams)
+{
+    return ReadBlockOrHeader(block, pos, consensusParams);
+}
+
+bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
+{
+    return ReadBlockOrHeader(block, pindex, consensusParams);
+}
+
+bool ReadBlockHeaderFromDisk(CBlockHeader& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
+{
+    return ReadBlockOrHeader(block, pindex, consensusParams);
+}
+
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& message_start)
 {
     CDiskBlockPos hpos = pos;
@@ -3080,7 +3101,7 @@ static bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos,
 static bool CheckBlockHeader(const CBlockHeader& block, CValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true)
 {
     // Check proof of work matches claimed amount
-    if (fCheckPOW && !CheckProofOfWork(block.GetPoWHash(), block.nBits, consensusParams))
+    if (fCheckPOW && !CheckAuxPowProofOfWork(block, consensusParams))
         return state.DoS(50, false, REJECT_INVALID, "high-hash", false, "proof of work failed");
 
     return true;
@@ -3231,6 +3252,22 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationSta
     assert(pindexPrev != nullptr);
     const int nHeight = pindexPrev->nHeight + 1;
 
+    // Disallow legacy blocks after merge-mining start.
+    if (!Params().GetConsensus().AllowLegacyBlocks(nHeight)
+        && block.IsLegacy())
+        return state.DoS(100, error("%s : legacy block after auxpow start",
+                                    __func__),
+                         REJECT_INVALID, "late-legacy-block");
+
+    // Dogecoin: Disallow AuxPow blocks before it is activated.
+    // TODO: Remove this test, as checkpoints will enforce this for us now
+    // NOTE: Previously this had its own fAllowAuxPoW flag, but that's always the opposite of fAllowLegacyBlocks
+    if (Params().GetConsensus().AllowLegacyBlocks(nHeight)
+        && block.IsAuxpow())
+        return state.DoS(100, error("%s : auxpow blocks are not allowed at height %d",
+                                    __func__, pindexPrev->nHeight + 1),
+                         REJECT_INVALID, "early-auxpow-block");
+
     // Check proof of work
     const Consensus::Params& consensusParams = params.GetConsensus();
     if (block.nBits != GetNextWorkRequired(pindexPrev, &block, consensusParams))
@@ -3257,10 +3294,10 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationSta
     // Reject outdated version blocks when 95% (75% on testnet) of the network has upgraded:
     // check for version 2, 3 and 4 upgrades
     // Dogecoin: Version 2 enforcement was never used
-    if((block.nVersion < 3 && nHeight >= consensusParams.BIP66Height) ||
-       (block.nVersion < 4 && nHeight >= consensusParams.BIP65Height))
-            return state.Invalid(false, REJECT_OBSOLETE, strprintf("bad-version(0x%08x)", block.nVersion),
-                                 strprintf("rejected nVersion=0x%08x block", block.nVersion));
+    if((block.GetBaseVersion() < 3 && nHeight >= consensusParams.BIP66Height) ||
+       (block.GetBaseVersion() < 4 && nHeight >= consensusParams.BIP65Height))
+            return state.Invalid(false, REJECT_OBSOLETE, strprintf("bad-version(0x%08x)", block.GetBaseVersion()),
+                                 strprintf("rejected nVersion=0x%08x block", block.GetBaseVersion()));
 
     return true;
 }
@@ -3276,6 +3313,7 @@ static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, c
     const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
 
     // Start enforcing BIP113 (Median Time Past) using versionbits logic.
+    // Dogecoin: We probably want to disable this
     int nLockTimeFlags = 0;
     if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_CSV, versionbitscache) == ThresholdState::ACTIVE) {
         nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
diff --git a/src/validation.h b/src/validation.h
index 4965ff152..acfbadd18 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -149,6 +149,7 @@ extern std::atomic_bool g_is_mempool_loaded;
 typedef std::unordered_map<uint256, CBlockIndex*, BlockHasher> BlockMap;
 extern BlockMap& mapBlockIndex;
 extern uint64_t nLastBlockTx;
+extern uint64_t nLastBlockSize;
 extern uint64_t nLastBlockWeight;
 extern const std::string strMessageMagic;
 extern CWaitableCriticalSection g_best_block_mutex;
@@ -393,6 +394,7 @@ bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus:
 bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& message_start);
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start);
+bool ReadBlockHeaderFromDisk(CBlockHeader& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
 
 /** Functions for validating blocks and updating the block tree */
 
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 193da7655..ce534a905 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -16,6 +16,7 @@
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
+#include <rpc/auxpow_miner.h>
 #include <rpc/mining.h>
 #include <rpc/rawtransaction.h>
 #include <rpc/server.h>
@@ -28,7 +29,6 @@
 #include <wallet/coincontrol.h>
 #include <wallet/feebumper.h>
 #include <wallet/rpcwallet.h>
-#include <wallet/wallet.h>
 #include <wallet/walletdb.h>
 #include <wallet/walletutil.h>
 
@@ -4759,6 +4759,75 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
     return result;
 }
 
+UniValue getauxblock(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    if (request.fHelp
+          || (request.params.size() != 0 && request.params.size() != 2))
+        throw std::runtime_error(
+            "getauxblock (hash auxpow)\n"
+            "\nCreate or submit a merge-mined block.\n"
+            "\nWithout arguments, create a new block and return information\n"
+            "required to merge-mine it.  With arguments, submit a solved\n"
+            "auxpow for a previously returned block.\n"
+            "\nArguments:\n"
+            "1. hash      (string, optional) hash of the block to submit\n"
+            "2. auxpow    (string, optional) serialised auxpow found\n"
+            "\nResult (without arguments):\n"
+            "{\n"
+            "  \"hash\"               (string) hash of the created block\n"
+            "  \"chainid\"            (numeric) chain ID for this block\n"
+            "  \"previousblockhash\"  (string) hash of the previous block\n"
+            "  \"coinbasevalue\"      (numeric) value of the block's coinbase\n"
+            "  \"bits\"               (string) compressed target of the block\n"
+            "  \"height\"             (numeric) height of the block\n"
+            "  \"_target\"            (string) target in reversed byte order, deprecated\n"
+            "}\n"
+            "\nResult (with arguments):\n"
+            "xxxxx        (boolean) whether the submitted block was correct\n"
+            "\nExamples:\n"
+            + HelpExampleCli("getauxblock", "")
+            + HelpExampleCli("getauxblock", "\"hash\" \"serialised auxpow\"")
+            + HelpExampleRpc("getauxblock", "")
+            );
+
+    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
+        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Private keys are disabled for this wallet");
+    }
+
+    std::shared_ptr<CReserveScript> coinbaseScript;
+    pwallet->GetScriptForMining(coinbaseScript);
+
+    /* If the keypool is exhausted, no script is returned at all.
+       Catch this.  */
+    if (!coinbaseScript)
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
+
+    /* Throw an error if no script was provided.  */
+    if (!coinbaseScript->reserveScript.size())
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "No coinbase script available (mining requires a wallet)");
+
+    /* Create a new block */
+    if (request.params.size() == 0)
+        return g_auxpow_miner->createAuxBlock(coinbaseScript->reserveScript);
+
+    /* Submit a block instead.  */
+    assert(request.params.size() == 2);
+    bool fAccepted
+        = g_auxpow_miner->submitAuxBlock(request.params[0].get_str(),
+                                         request.params[1].get_str());
+    if (fAccepted)
+        coinbaseScript->KeepScript();
+
+    return fAccepted;
+}
+
 extern UniValue abortrescan(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue dumpprivkey(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue importprivkey(const JSONRPCRequest& request);
@@ -4844,6 +4913,7 @@ static const CRPCCommand commands[] =
     { "wallet",             "setlabel",                         &setlabel,                      {"address","label"} },
 
     { "generating",         "generate",                         &generate,                      {"nblocks","maxtries"} },
+    { "mining",             "getauxblock",                      &getauxblock,                   {"hash", "auxpow"} },
 };
 
 void RegisterWalletRPCCommands(CRPCTable &t)
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 7b791ae41..ae5de3e85 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -7,6 +7,7 @@
 #define BITCOIN_WALLET_WALLET_H
 
 #include <amount.h>
+#include <auxpow.h> // contains CBaseMerkleTx
 #include <outputtype.h>
 #include <policy/feerate.h>
 #include <streams.h>
@@ -208,58 +209,21 @@ struct COutputEntry
 };
 
 /** A transaction with a merkle branch linking it to the block chain. */
-class CMerkleTx
+class CMerkleTx : public CBaseMerkleTx
 {
 private:
   /** Constant used in hashBlock to indicate tx has been abandoned */
     static const uint256 ABANDON_HASH;
 
 public:
-    CTransactionRef tx;
-    uint256 hashBlock;
 
-    /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
-     * block in the chain we know this or any in-wallet dependency conflicts
-     * with. Older clients interpret nIndex == -1 as unconfirmed for backward
-     * compatibility.
-     */
-    int nIndex;
-
-    CMerkleTx()
-    {
-        SetTx(MakeTransactionRef());
-        Init();
-    }
+    CMerkleTx() = default;
 
     explicit CMerkleTx(CTransactionRef arg)
-    {
-        SetTx(std::move(arg));
-        Init();
-    }
+      : CBaseMerkleTx(arg)
+    {}
 
-    void Init()
-    {
-        hashBlock = uint256();
-        nIndex = -1;
-    }
-
-    void SetTx(CTransactionRef arg)
-    {
-        tx = std::move(arg);
-    }
-
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        std::vector<uint256> vMerkleBranch; // For compatibility with older versions.
-        READWRITE(tx);
-        READWRITE(hashBlock);
-        READWRITE(vMerkleBranch);
-        READWRITE(nIndex);
-    }
-
-    void SetMerkleBranch(const CBlockIndex* pIndex, int posInBlock);
+    void SetMerkleBranch(const CBlockIndex* pindex, int posInBlock);
 
     /**
      * Return depth of transaction in blockchain:
@@ -274,7 +238,6 @@ public:
     bool isAbandoned() const { return (hashBlock == ABANDON_HASH); }
     void setAbandoned() { hashBlock = ABANDON_HASH; }
 
-    const uint256& GetHash() const { return tx->GetHash(); }
     bool IsCoinBase() const { return tx->IsCoinBase(); }
 };
 
diff --git a/test/functional/auxpow_mining.py b/test/functional/auxpow_mining.py
new file mode 100755
index 000000000..bb4568772
--- /dev/null
+++ b/test/functional/auxpow_mining.py
@@ -0,0 +1,188 @@
+#!/usr/bin/env python3
+# Copyright (c) 2014-2018 Daniel Kraft
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+# Test the merge-mining RPC interface:
+# getauxblock, createauxblock, submitauxblock
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import *
+
+from test_framework.auxpow import reverseHex
+from test_framework.auxpow_testing import (
+  computeAuxpow,
+  getCoinbaseAddr,
+  mineAuxpowBlockWithMethods,
+)
+
+class AuxpowMiningTest (BitcoinTestFramework):
+
+  def set_test_params (self):
+    self.num_nodes = 2
+
+  def add_options (self, parser):
+    parser.add_argument ("--segwit", dest="segwit", default=False,
+                         action="store_true",
+                         help="Test behaviour with SegWit active")
+
+  def run_test (self):
+    # Enable mock time to be out of IBD.
+    self.enable_mocktime ()
+
+    # Activate segwit if requested.
+    if self.options.segwit:
+      self.nodes[0].generate (500)
+      self.sync_all ()
+
+    # Test with getauxblock and createauxblock/submitauxblock.
+    self.test_getauxblock ()
+    self.test_create_submit_auxblock ()
+
+  def test_common (self, create, submit):
+    """
+    Common test code that is shared between the tests for getauxblock and the
+    createauxblock / submitauxblock method pair.
+    """
+
+    # Verify data that can be found in another way.
+    auxblock = create ()
+    assert_equal (auxblock['chainid'], 1)
+    assert_equal (auxblock['height'], self.nodes[0].getblockcount () + 1)
+    assert_equal (auxblock['previousblockhash'],
+                  self.nodes[0].getblockhash (auxblock['height'] - 1))
+
+    # Calling again should give the same block.
+    auxblock2 = create ()
+    assert_equal (auxblock2, auxblock)
+
+    # If we receive a new block, the old hash will be replaced.
+    self.sync_all ()
+    self.nodes[1].generate (1)
+    self.sync_all ()
+    auxblock2 = create ()
+    assert auxblock['hash'] != auxblock2['hash']
+    assert_raises_rpc_error (-8, 'block hash unknown', submit,
+                             auxblock['hash'], "x")
+
+    # Invalid format for auxpow.
+    assert_raises_rpc_error (-1, None, submit,
+                             auxblock2['hash'], "x")
+
+    # Invalidate the block again, send a transaction and query for the
+    # auxblock to solve that contains the transaction.
+    self.nodes[0].generate (1)
+    addr = self.nodes[1].getnewaddress ()
+    txid = self.nodes[0].sendtoaddress (addr, 1)
+    self.sync_all ()
+    assert_equal (self.nodes[1].getrawmempool (), [txid])
+    auxblock = create ()
+    target = reverseHex (auxblock['_target'])
+
+    # Compute invalid auxpow.
+    apow = computeAuxpow (auxblock['hash'], target, False)
+    res = submit (auxblock['hash'], apow)
+    assert not res
+
+    # Compute and submit valid auxpow.
+    apow = computeAuxpow (auxblock['hash'], target, True)
+    res = submit (auxblock['hash'], apow)
+    assert res
+
+    # Make sure that the block is indeed accepted.
+    self.sync_all ()
+    assert_equal (self.nodes[1].getrawmempool (), [])
+    height = self.nodes[1].getblockcount ()
+    assert_equal (height, auxblock['height'])
+    assert_equal (self.nodes[1].getblockhash (height), auxblock['hash'])
+
+    # Call getblock and verify the auxpow field.
+    data = self.nodes[1].getblock (auxblock['hash'])
+    assert 'auxpow' in data
+    auxJson = data['auxpow']
+    assert_equal (auxJson['index'], 0)
+    assert_equal (auxJson['chainindex'], 0)
+    assert_equal (auxJson['merklebranch'], [])
+    assert_equal (auxJson['chainmerklebranch'], [])
+    assert_equal (auxJson['parentblock'], apow[-160:])
+
+    # Also previous blocks should have 'auxpow', since all blocks (also
+    # those generated by "generate") are merge-mined.
+    oldHash = self.nodes[1].getblockhash (100)
+    data = self.nodes[1].getblock (oldHash)
+    assert 'auxpow' in data
+
+    # Check that it paid correctly to the first node.
+    t = self.nodes[0].listtransactions ("*", 1)
+    assert_equal (len (t), 1)
+    t = t[0]
+    assert_equal (t['category'], "immature")
+    assert_equal (t['blockhash'], auxblock['hash'])
+    assert t['generated']
+    assert_greater_than_or_equal (t['amount'], Decimal ("1"))
+    assert_equal (t['confirmations'], 1)
+
+    # Verify the coinbase script.  Ensure that it includes the block height
+    # to make the coinbase tx unique.  The expected block height is around
+    # 200, so that the serialisation of the CScriptNum ends in an extra 00.
+    # The vector has length 2, which makes up for 02XX00 as the serialised
+    # height.  Check this.  (With segwit, the height is different, so we skip
+    # this for simplicity.)
+    if not self.options.segwit:
+      blk = self.nodes[1].getblock (auxblock['hash'])
+      tx = self.nodes[1].getrawtransaction (blk['tx'][0], 1)
+      coinbase = tx['vin'][0]['coinbase']
+      assert_equal ("02%02x00" % auxblock['height'], coinbase[0 : 6])
+
+  def test_getauxblock (self):
+    """
+    Test the getauxblock method.
+    """
+
+    create = self.nodes[0].getauxblock
+    submit = self.nodes[0].getauxblock
+    self.test_common (create, submit)
+
+    # Ensure that the payout address is changed from one block to the next.
+    hash1 = mineAuxpowBlockWithMethods (create, submit)
+    hash2 = mineAuxpowBlockWithMethods (create, submit)
+    self.sync_all ()
+    addr1 = getCoinbaseAddr (self.nodes[1], hash1)
+    addr2 = getCoinbaseAddr (self.nodes[1], hash2)
+    assert addr1 != addr2
+    info = self.nodes[0].getaddressinfo (addr1)
+    assert info['ismine']
+    info = self.nodes[0].getaddressinfo (addr2)
+    assert info['ismine']
+
+  def test_create_submit_auxblock (self):
+    """
+    Test the createauxblock / submitauxblock method pair.
+    """
+
+    # Check for errors with wrong parameters.
+    assert_raises_rpc_error (-1, None, self.nodes[0].createauxblock)
+    assert_raises_rpc_error (-5, "Invalid coinbase payout address",
+                             self.nodes[0].createauxblock,
+                             "this_an_invalid_address")
+
+    # Fix a coinbase address and construct methods for it.
+    coinbaseAddr = self.nodes[0].getnewaddress ()
+    def create ():
+      return self.nodes[0].createauxblock (coinbaseAddr)
+    submit = self.nodes[0].submitauxblock
+
+    # Run common tests.
+    self.test_common (create, submit)
+
+    # Ensure that the payout address is the one which we specify
+    hash1 = mineAuxpowBlockWithMethods (create, submit)
+    hash2 = mineAuxpowBlockWithMethods (create, submit)
+    self.sync_all ()
+    addr1 = getCoinbaseAddr (self.nodes[1], hash1)
+    addr2 = getCoinbaseAddr (self.nodes[1], hash2)
+    assert_equal (addr1, coinbaseAddr)
+    assert_equal (addr2, coinbaseAddr)
+
+if __name__ == '__main__':
+  AuxpowMiningTest ().main ()
diff --git a/test/functional/interface_rest.py b/test/functional/interface_rest.py
index afa9de580..2ae7b7c94 100755
--- a/test/functional/interface_rest.py
+++ b/test/functional/interface_rest.py
@@ -14,6 +14,7 @@ from struct import pack, unpack
 import http.client
 import urllib.parse
 
+from test_framework import auxpow
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -175,7 +176,13 @@ class RESTTest (BitcoinTestFramework):
         assert_equal(len(json_obj['utxos']), 0)
 
         self.nodes[0].generate(1)
+
+        json_request = json_request.rstrip("/")
+        response = http_post_call(url.hostname, url.port, '/rest/getutxos'+json_request+self.FORMAT_SEPARATOR+'json', '', True)
+        assert_equal(response.status, 200) #must be a 200 because we are within the limits
+
         self.sync_all()
+        bb_hash = self.nodes[0].getbestblockhash()
 
         json_obj = self.test_rest_request("/getutxos/{}-{}".format(*spending))
         assert_equal(len(json_obj['utxos']), 1)
@@ -195,7 +202,7 @@ class RESTTest (BitcoinTestFramework):
         long_uri = '/'.join(['{}-{}'.format(txid, n_) for n_ in range(15)])
         self.test_rest_request("/getutxos/checkmempool/{}".format(long_uri), http_method='POST', status=200)
 
-        self.nodes[0].generate(1)  # generate block to not affect upcoming tests
+        mineAuxpowBlock(self.nodes[0])  # generate block to not affect upcoming tests
         self.sync_all()
 
         self.log.info("Test the /block and /headers URIs")
@@ -208,9 +215,10 @@ class RESTTest (BitcoinTestFramework):
 
         # Compare with block header
         response_header = self.test_rest_request("/headers/1/{}".format(bb_hash), req_type=ReqType.BIN, ret_type=RetType.OBJ)
-        assert_equal(int(response_header.getheader('content-length')), 80)
+        headerLen = int(response_header.getheader('content-length'))
+        assert_greater_than(headerLen, 80)
         response_header_bytes = response_header.read()
-        assert_equal(response_bytes[:80], response_header_bytes)
+        assert_equal(response_bytes[:headerLen], response_header_bytes)
 
         # Check block hex format
         response_hex = self.test_rest_request("/block/{}".format(bb_hash), req_type=ReqType.HEX, ret_type=RetType.OBJ)
@@ -221,8 +229,10 @@ class RESTTest (BitcoinTestFramework):
         # Compare with hex block header
         response_header_hex = self.test_rest_request("/headers/1/{}".format(bb_hash), req_type=ReqType.HEX, ret_type=RetType.OBJ)
         assert_greater_than(int(response_header_hex.getheader('content-length')), 160)
-        response_header_hex_bytes = response_header_hex.read(160)
-        assert_equal(binascii.hexlify(response_bytes[:80]), response_header_hex_bytes)
+        response_header_hex_bytes = response_header_hex.read().strip()
+        headerLen = len (response_header_hex_bytes)
+        assert_equal(binascii.hexlify(response_bytes[:headerLen]), response_header_hex_bytes)
+        assert_equal(encode(response_header_bytes, "hex_codec"), response_header_hex_bytes)
 
         # Check json format
         block_json_obj = self.test_rest_request("/block/{}".format(bb_hash))
diff --git a/test/functional/test_framework/auxpow.py b/test/functional/test_framework/auxpow.py
new file mode 100644
index 000000000..e145e7ce7
--- /dev/null
+++ b/test/functional/test_framework/auxpow.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+# Copyright (c) 2014-2018 Daniel Kraft
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+# Basic code for working with auxpow.  This is used for the regtests (e.g. from
+# auxpow_testing.py), but also for contrib/auxpow/getwork-wrapper.py.
+
+import binascii
+import codecs
+import hashlib
+
+def constructAuxpow (block):
+  """
+  Starts to construct a minimal auxpow, ready to be mined.  Returns the fake
+  coinbase tx and the unmined parent block header as hex strings.
+  """
+
+  block = codecs.encode (block, 'ascii')
+
+  # Start by building the merge-mining coinbase.  The merkle tree
+  # consists only of the block hash as root.
+  coinbase = b"fabe" + binascii.hexlify (b"m" * 2)
+  coinbase += block
+  coinbase += b"01000000" + (b"00" * 4)
+
+  # Construct "vector" of transaction inputs.
+  vin = b"01"
+  vin += (b"00" * 32) + (b"ff" * 4)
+  vin += codecs.encode ("%02x" % (len (coinbase) // 2), "ascii") + coinbase
+  vin += (b"ff" * 4)
+
+  # Build up the full coinbase transaction.  It consists only
+  # of the input and has no outputs.
+  tx = b"01000000" + vin + b"00" + (b"00" * 4)
+  txHash = doubleHashHex (tx)
+
+  # Construct the parent block header.  It need not be valid, just good
+  # enough for auxpow purposes.
+  header = b"01000000"
+  header += b"00" * 32
+  header += reverseHex (txHash)
+  header += b"00" * 4
+  header += b"00" * 4
+  header += b"00" * 4
+
+  return (tx.decode ('ascii'), header.decode ('ascii'))
+
+def finishAuxpow (tx, header):
+  """
+  Constructs the finished auxpow hex string based on the mined header.
+  """
+
+  blockhash = doubleHashHex (header)
+
+  # Build the MerkleTx part of the auxpow.
+  auxpow = codecs.encode (tx, 'ascii')
+  auxpow += blockhash
+  auxpow += b"00"
+  auxpow += b"00" * 4
+
+  # Extend to full auxpow.
+  auxpow += b"00"
+  auxpow += b"00" * 4
+  auxpow += header
+
+  return auxpow.decode ("ascii")
+
+def doubleHashHex (data):
+  """
+  Perform Bitcoin's Double-SHA256 hash on the given hex string.
+  """
+
+  hasher = hashlib.sha256 ()
+  hasher.update (binascii.unhexlify (data))
+  data = hasher.digest ()
+
+  hasher = hashlib.sha256 ()
+  hasher.update (data)
+
+  return reverseHex (hasher.hexdigest ())
+
+def reverseHex (data):
+  """
+  Flip byte order in the given data (hex string).
+  """
+
+  b = bytearray (binascii.unhexlify (data))
+  b.reverse ()
+
+  return binascii.hexlify (b)
+
+def getworkByteswap (data):
+  """
+  Run the byte-order swapping step necessary for working with getwork.
+  """
+
+  data = bytearray (data)
+  assert len (data) % 4 == 0
+  for i in range (0, len (data), 4):
+    data[i], data[i + 3] = data[i + 3], data[i]
+    data[i + 1], data[i + 2] = data[i + 2], data[i + 1]
+
+  return data
diff --git a/test/functional/test_framework/auxpow_testing.py b/test/functional/test_framework/auxpow_testing.py
new file mode 100644
index 000000000..f1ef056b8
--- /dev/null
+++ b/test/functional/test_framework/auxpow_testing.py
@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+# Copyright (c) 2014-2018 Daniel Kraft
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+# Utility routines for auxpow that are needed specifically by the regtests.
+# This is mostly about actually *solving* an auxpow block (with regtest
+# difficulty) or inspecting the information for verification.
+
+import binascii
+
+from test_framework import auxpow
+
+def computeAuxpow (block, target, ok):
+  """
+  Build an auxpow object (serialised as hex string) that solves
+  (ok = True) or doesn't solve (ok = False) the block.
+  """
+
+  (tx, header) = auxpow.constructAuxpow (block)
+  (header, _) = mineBlock (header, target, ok)
+  return auxpow.finishAuxpow (tx, header)
+
+def mineAuxpowBlock (node):
+  """
+  Mine an auxpow block on the given RPC connection.  This uses the
+  createauxblock and submitauxblock command pair.
+  """
+
+  def create ():
+    addr = node.getnewaddress ()
+    return node.createauxblock (addr)
+
+  return mineAuxpowBlockWithMethods (create, node.submitauxblock)
+
+def mineAuxpowBlockWithMethods (create, submit):
+  """
+  Mine an auxpow block, using the given methods for creation and submission.
+  """
+
+  auxblock = create ()
+  target = auxpow.reverseHex (auxblock['_target'])
+  apow = computeAuxpow (auxblock['hash'], target, True)
+  res = submit (auxblock['hash'], apow)
+  assert res
+
+  return auxblock['hash']
+
+def getCoinbaseAddr (node, blockHash):
+    """
+    Extract the coinbase tx' payout address for the given block.
+    """
+
+    blockData = node.getblock (blockHash)
+    txn = blockData['tx']
+    assert len (txn) >= 1
+
+    txData = node.getrawtransaction (txn[0], 1)
+    assert len (txData['vout']) >= 1 and len (txData['vin']) == 1
+    assert 'coinbase' in txData['vin'][0]
+
+    addr = txData['vout'][0]['scriptPubKey']['addresses']
+    assert len (addr) == 1
+    return addr[0]
+
+def mineBlock (header, target, ok):
+  """
+  Given a block header, update the nonce until it is ok (or not)
+  for the given target.
+  """
+
+  data = bytearray (binascii.unhexlify (header))
+  while True:
+    assert data[79] < 255
+    data[79] += 1
+    hexData = binascii.hexlify (data)
+
+    blockhash = auxpow.doubleHashHex (hexData)
+    if (ok and blockhash < target) or ((not ok) and blockhash > target):
+      break
+
+  return (hexData, blockhash)