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BIP32 derivation implementation

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This commit is contained in:
Pieter Wuille 2013-07-15 01:05:25 +02:00
parent 8388289eb6
commit eb2c999050
5 changed files with 258 additions and 0 deletions
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26
src/base58.h
View file

@ -390,4 +390,30 @@ public:
}
};
template<typename K, int Size, CChainParams::Base58Type Type> class CBitcoinExtKeyBase : public CBase58Data
{
public:
void SetKey(const K &key) {
unsigned char vch[Size];
key.Encode(vch);
SetData(Params().Base58Prefix(Type), vch, vch+Size);
}
K GetKey() {
K ret;
ret.Decode(&vchData[0], &vchData[Size]);
return ret;
}
CBitcoinExtKeyBase(const K &key) {
SetKey(key);
}
CBitcoinExtKeyBase() {}
};
typedef CBitcoinExtKeyBase<CExtKey, 74, CChainParams::EXT_SECRET_KEY> CBitcoinExtKey;
typedef CBitcoinExtKeyBase<CExtPubKey, 74, CChainParams::EXT_PUBLIC_KEY> CBitcoinExtPubKey;
#endif // BITCOIN_BASE58_H

4
src/chainparams.cpp
View file

@ -147,6 +147,8 @@ public:
base58Prefixes[PUBKEY_ADDRESS] = list_of(0);
base58Prefixes[SCRIPT_ADDRESS] = list_of(5);
base58Prefixes[SECRET_KEY] = list_of(128);
base58Prefixes[EXT_PUBLIC_KEY] = list_of(0x04)(0x88)(0xB2)(0x1E);
base58Prefixes[EXT_SECRET_KEY] = list_of(0x04)(0x88)(0xAD)(0xE4);
// Convert the pnSeeds array into usable address objects.
for (unsigned int i = 0; i < ARRAYLEN(pnSeed); i++)
@ -209,6 +211,8 @@ public:
base58Prefixes[PUBKEY_ADDRESS] = list_of(111);
base58Prefixes[SCRIPT_ADDRESS] = list_of(196);
base58Prefixes[SECRET_KEY] = list_of(239);
base58Prefixes[EXT_PUBLIC_KEY] = list_of(0x04)(0x35)(0x87)(0xCF);
base58Prefixes[EXT_SECRET_KEY] = list_of(0x04)(0x35)(0x83)(0x94);
}
virtual Network NetworkID() const { return CChainParams::TESTNET; }
};

2
src/chainparams.h
View file

@ -45,6 +45,8 @@ public:
PUBKEY_ADDRESS,
SCRIPT_ADDRESS,
SECRET_KEY,
EXT_PUBLIC_KEY,
EXT_SECRET_KEY,
MAX_BASE58_TYPES
};

180
src/key.cpp
View file

@ -2,6 +2,7 @@
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <openssl/bn.h>
#include <openssl/ecdsa.h>
#include <openssl/rand.h>
#include <openssl/obj_mac.h>
@ -253,6 +254,57 @@ public:
ECDSA_SIG_free(sig);
return ret;
}
static bool TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32])
{
bool ret = true;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
BIGNUM *bnSecret = BN_CTX_get(ctx);
BIGNUM *bnTweak = BN_CTX_get(ctx);
BIGNUM *bnOrder = BN_CTX_get(ctx);
EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_secp256k1);
EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
BN_bin2bn(vchTweak, 32, bnTweak);
if (BN_cmp(bnTweak, bnOrder) >= 0)
ret = false; // extremely unlikely
BN_bin2bn(vchSecretIn, 32, bnSecret);
BN_add(bnSecret, bnSecret, bnTweak);
BN_nnmod(bnSecret, bnSecret, bnOrder, ctx);
if (BN_is_zero(bnSecret))
ret = false; // ridiculously unlikely
int nBits = BN_num_bits(bnSecret);
memset(vchSecretOut, 0, 32);
BN_bn2bin(bnSecret, &vchSecretOut[32-(nBits+7)/8]);
EC_GROUP_free(group);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
bool TweakPublic(const unsigned char vchTweak[32]) {
bool ret = true;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
BIGNUM *bnTweak = BN_CTX_get(ctx);
BIGNUM *bnOrder = BN_CTX_get(ctx);
BIGNUM *bnOne = BN_CTX_get(ctx);
const EC_GROUP *group = EC_KEY_get0_group(pkey);
EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
BN_bin2bn(vchTweak, 32, bnTweak);
if (BN_cmp(bnTweak, bnOrder) >= 0)
ret = false; // extremely unlikely
EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group);
BN_one(bnOne);
EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx);
if (EC_POINT_is_at_infinity(group, point))
ret = false; // ridiculously unlikely
EC_KEY_set_public_key(pkey, point);
EC_POINT_free(point);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
};
}; // end of anonymous namespace
@ -393,3 +445,131 @@ bool CPubKey::Decompress() {
key.GetPubKey(*this, false);
return true;
}
void static BIP32Hash(const unsigned char chainCode[32], unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64]) {
unsigned char num[4];
num[0] = (nChild >> 24) & 0xFF;
num[1] = (nChild >> 16) & 0xFF;
num[2] = (nChild >> 8) & 0xFF;
num[3] = (nChild >> 0) & 0xFF;
HMAC_SHA512_CTX ctx;
HMAC_SHA512_Init(&ctx, chainCode, 32);
HMAC_SHA512_Update(&ctx, &header, 1);
HMAC_SHA512_Update(&ctx, data, 32);
HMAC_SHA512_Update(&ctx, num, 4);
HMAC_SHA512_Final(output, &ctx);
}
bool CKey::Derive(CKey& keyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const {
assert(IsValid());
assert(IsCompressed());
unsigned char out[64];
LockObject(out);
if ((nChild >> 31) == 0) {
CPubKey pubkey = GetPubKey();
assert(pubkey.begin() + 33 == pubkey.end());
BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, out);
} else {
assert(begin() + 32 == end());
BIP32Hash(cc, nChild, 0, begin(), out);
}
memcpy(ccChild, out+32, 32);
bool ret = CECKey::TweakSecret((unsigned char*)keyChild.begin(), begin(), out);
UnlockObject(out);
keyChild.fCompressed = true;
keyChild.fValid = ret;
return ret;
}
bool CPubKey::Derive(CPubKey& pubkeyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const {
assert(IsValid());
assert((nChild >> 31) == 0);
assert(begin() + 33 == end());
unsigned char out[64];
BIP32Hash(cc, nChild, *begin(), begin()+1, out);
memcpy(ccChild, out+32, 32);
CECKey key;
bool ret = key.SetPubKey(*this);
ret &= key.TweakPublic(out);
key.GetPubKey(pubkeyChild, true);
return ret;
}
bool CExtKey::Derive(CExtKey &out, unsigned int nChild) const {
out.nDepth = nDepth + 1;
CKeyID id = key.GetPubKey().GetID();
memcpy(&out.vchFingerprint[0], &id, 4);
out.nChild = nChild;
return key.Derive(out.key, out.vchChainCode, nChild, vchChainCode);
}
void CExtKey::SetMaster(const unsigned char *seed, unsigned int nSeedLen) {
static const char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
HMAC_SHA512_CTX ctx;
HMAC_SHA512_Init(&ctx, hashkey, sizeof(hashkey));
HMAC_SHA512_Update(&ctx, seed, nSeedLen);
unsigned char out[64];
LockObject(out);
HMAC_SHA512_Final(out, &ctx);
key.Set(&out[0], &out[32], true);
memcpy(vchChainCode, &out[32], 32);
UnlockObject(out);
nDepth = 0;
nChild = 0;
memset(vchFingerprint, 0, sizeof(vchFingerprint));
}
CExtPubKey CExtKey::Neuter() const {
CExtPubKey ret;
ret.nDepth = nDepth;
memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
ret.nChild = nChild;
ret.pubkey = key.GetPubKey();
memcpy(&ret.vchChainCode[0], &vchChainCode[0], 32);
return ret;
}
void CExtKey::Encode(unsigned char code[74]) const {
code[0] = nDepth;
memcpy(code+1, vchFingerprint, 4);
code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
memcpy(code+9, vchChainCode, 32);
code[41] = 0;
assert(key.size() == 32);
memcpy(code+42, key.begin(), 32);
}
void CExtKey::Decode(const unsigned char code[74]) {
nDepth = code[0];
memcpy(vchFingerprint, code+1, 4);
nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
memcpy(vchChainCode, code+9, 32);
key.Set(code+42, code+74, true);
}
void CExtPubKey::Encode(unsigned char code[74]) const {
code[0] = nDepth;
memcpy(code+1, vchFingerprint, 4);
code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
memcpy(code+9, vchChainCode, 32);
assert(pubkey.size() == 33);
memcpy(code+41, pubkey.begin(), 33);
}
void CExtPubKey::Decode(const unsigned char code[74]) {
nDepth = code[0];
memcpy(vchFingerprint, code+1, 4);
nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
memcpy(vchChainCode, code+9, 32);
pubkey.Set(code+41, code+74);
}
bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const {
out.nDepth = nDepth + 1;
CKeyID id = pubkey.GetID();
memcpy(&out.vchFingerprint[0], &id, 4);
out.nChild = nChild;
return pubkey.Derive(out.pubkey, out.vchChainCode, nChild, vchChainCode);
}

46
src/key.h
View file

@ -161,6 +161,9 @@ public:
// Turn this public key into an uncompressed public key.
bool Decompress();
// Derive BIP32 child pubkey.
bool Derive(CPubKey& pubkeyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const;
};
@ -201,6 +204,10 @@ public:
UnlockObject(vch);
}
friend bool operator==(const CKey &a, const CKey &b) {
return a.fCompressed == b.fCompressed && memcmp(&a.vch[0], &b.vch[0], 32);
}
// Initialize using begin and end iterators to byte data.
template<typename T>
void Set(const T pbegin, const T pend, bool fCompressedIn) {
@ -251,6 +258,45 @@ public:
// 0x1D = second key with even y, 0x1E = second key with odd y,
// add 0x04 for compressed keys.
bool SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const;
// Derive BIP32 child key.
bool Derive(CKey& keyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const;
};
struct CExtPubKey {
unsigned char nDepth;
unsigned char vchFingerprint[4];
unsigned int nChild;
unsigned char vchChainCode[32];
CPubKey pubkey;
friend bool operator==(const CExtPubKey &a, const CExtPubKey &b) {
return a.nDepth == b.nDepth && memcmp(&a.vchFingerprint[0], &b.vchFingerprint[0], 4) == 0 && a.nChild == b.nChild &&
memcmp(&a.vchChainCode[0], &b.vchChainCode[0], 32) == 0 && a.pubkey == b.pubkey;
}
void Encode(unsigned char code[74]) const;
void Decode(const unsigned char code[74]);
bool Derive(CExtPubKey &out, unsigned int nChild) const;
};
struct CExtKey {
unsigned char nDepth;
unsigned char vchFingerprint[4];
unsigned int nChild;
unsigned char vchChainCode[32];
CKey key;
friend bool operator==(const CExtKey &a, const CExtKey &b) {
return a.nDepth == b.nDepth && memcmp(&a.vchFingerprint[0], &b.vchFingerprint[0], 4) == 0 && a.nChild == b.nChild &&
memcmp(&a.vchChainCode[0], &b.vchChainCode[0], 32) == 0 && a.key == b.key;
}
void Encode(unsigned char code[74]) const;
void Decode(const unsigned char code[74]);
bool Derive(CExtKey &out, unsigned int nChild) const;
CExtPubKey Neuter() const;
void SetMaster(const unsigned char *seed, unsigned int nSeedLen);
};
#endif