Precompute sighashes

Original version by Nicolas Dorier. Precomputing version by Pieter Wuille.

1 files changed, 37 insertions, 17 deletions

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index bc027e9f0c..459feaa0f4 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1108,9 +1108,40 @@ public:
     }
 };
 
+uint256 GetPrevoutHash(const CTransaction& txTo) {
+    CHashWriter ss(SER_GETHASH, 0);
+    for (unsigned int n = 0; n < txTo.vin.size(); n++) {
+        ss << txTo.vin[n].prevout;
+    }
+    return ss.GetHash();
+}
+
+uint256 GetSequenceHash(const CTransaction& txTo) {
+    CHashWriter ss(SER_GETHASH, 0);
+    for (unsigned int n = 0; n < txTo.vin.size(); n++) {
+        ss << txTo.vin[n].nSequence;
+    }
+    return ss.GetHash();
+}
+
+uint256 GetOutputsHash(const CTransaction& txTo) {
+    CHashWriter ss(SER_GETHASH, 0);
+    for (unsigned int n = 0; n < txTo.vout.size(); n++) {
+        ss << txTo.vout[n];
+    }
+    return ss.GetHash();
+}
+
 } // anon namespace
 
-uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion)
+CachedHashes::CachedHashes(const CTransaction& txTo)
+{
+    hashPrevouts = GetPrevoutHash(txTo);
+    hashSequence = GetSequenceHash(txTo);
+    hashOutputs = GetOutputsHash(txTo);
+}
+
+uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const CachedHashes* cache)
 {
     if (sigversion == SIGVERSION_WITNESS_V0) {
         uint256 hashPrevouts;
@@ -1118,27 +1149,16 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
         uint256 hashOutputs;
 
         if (!(nHashType & SIGHASH_ANYONECANPAY)) {
-            CHashWriter ss(SER_GETHASH, 0);
-            for (unsigned int n = 0; n < txTo.vin.size(); n++) {
-                ss << txTo.vin[n].prevout;
-            }
-            hashPrevouts = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
+            hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
         }
 
         if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            CHashWriter ss(SER_GETHASH, 0);
-            for (unsigned int n = 0; n < txTo.vin.size(); n++) {
-                ss << txTo.vin[n].nSequence;
-            }
-            hashSequence = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
+            hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
         }
 
+
         if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            CHashWriter ss(SER_GETHASH, 0);
-            for (unsigned int n = 0; n < txTo.vout.size(); n++) {
-                ss << txTo.vout[n];
-            }
-            hashOutputs = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
+            hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
         } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
             CHashWriter ss(SER_GETHASH, 0);
             ss << txTo.vout[nIn];
@@ -1209,7 +1229,7 @@ bool TransactionSignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn
     int nHashType = vchSig.back();
     vchSig.pop_back();
 
-    uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion);
+    uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion, this->cachedHashes);
 
     if (!VerifySignature(vchSig, pubkey, sighash))
         return false;