diff --git a/scripts/hash_history.py b/scripts/hash_history.py
new file mode 100644
index 000000000..bdad530af
--- /dev/null
+++ b/scripts/hash_history.py
@@ -0,0 +1,69 @@
+from synapse.storage.pdu import PduStore
+from synapse.storage.signatures import SignatureStore
+from synapse.storage._base import SQLBaseStore
+from synapse.federation.units import Pdu
+from synapse.crypto.event_signing import (
+    add_event_pdu_content_hash, compute_pdu_event_reference_hash
+)
+from synapse.api.events.utils import prune_pdu
+from syutil.base64util import encode_base64, decode_base64
+from syutil.jsonutil import encode_canonical_json
+import sqlite3
+import sys
+
+class Store(object):
+    _get_pdu_tuples = PduStore.__dict__["_get_pdu_tuples"]
+    _get_pdu_content_hashes_txn = SignatureStore.__dict__["_get_pdu_content_hashes_txn"]
+    _get_prev_pdu_hashes_txn = SignatureStore.__dict__["_get_prev_pdu_hashes_txn"]
+    _get_pdu_origin_signatures_txn = SignatureStore.__dict__["_get_pdu_origin_signatures_txn"]
+    _store_pdu_content_hash_txn = SignatureStore.__dict__["_store_pdu_content_hash_txn"]
+    _store_pdu_reference_hash_txn = SignatureStore.__dict__["_store_pdu_reference_hash_txn"]
+    _store_prev_pdu_hash_txn = SignatureStore.__dict__["_store_prev_pdu_hash_txn"]
+    _simple_insert_txn = SQLBaseStore.__dict__["_simple_insert_txn"]
+
+
+store = Store()
+
+
+def select_pdus(cursor):
+    cursor.execute(
+        "SELECT pdu_id, origin FROM pdus ORDER BY depth ASC"
+    )
+
+    ids = cursor.fetchall()
+
+    pdu_tuples = store._get_pdu_tuples(cursor, ids)
+
+    pdus = [Pdu.from_pdu_tuple(p) for p in pdu_tuples]
+
+    reference_hashes = {}
+
+    for pdu in pdus:
+        try:
+            if pdu.prev_pdus:
+                print "PROCESS", pdu.pdu_id, pdu.origin, pdu.prev_pdus
+                for pdu_id, origin, hashes in pdu.prev_pdus:
+                    ref_alg, ref_hsh = reference_hashes[(pdu_id, origin)]
+                    hashes[ref_alg] = encode_base64(ref_hsh)
+                    store._store_prev_pdu_hash_txn(cursor,  pdu.pdu_id, pdu.origin, pdu_id, origin, ref_alg, ref_hsh)
+                print "SUCCESS", pdu.pdu_id, pdu.origin, pdu.prev_pdus
+            pdu = add_event_pdu_content_hash(pdu)
+            ref_alg, ref_hsh = compute_pdu_event_reference_hash(pdu)
+            reference_hashes[(pdu.pdu_id, pdu.origin)] = (ref_alg, ref_hsh)
+            store._store_pdu_reference_hash_txn(cursor, pdu.pdu_id, pdu.origin, ref_alg, ref_hsh)
+
+            for alg, hsh_base64 in pdu.hashes.items():
+                print alg, hsh_base64
+                store._store_pdu_content_hash_txn(cursor, pdu.pdu_id, pdu.origin, alg, decode_base64(hsh_base64))
+
+        except:
+            print "FAILED_", pdu.pdu_id, pdu.origin, pdu.prev_pdus
+
+def main():
+    conn = sqlite3.connect(sys.argv[1])
+    cursor = conn.cursor()
+    select_pdus(cursor)
+    conn.commit()
+
+if __name__=='__main__':
+    main()