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Merge pull request #6918

69d373f Don't wipe the sigcache in TestBlockValidity (Pieter Wuille)
0b9e9dc Evict sigcache entries that are seen in a block (Pieter Wuille)
830e3f3 Make sigcache faster and more efficient (Pieter Wuille)
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laanwj committed Nov 12, 2015
2 parents 54e8bfe + 69d373f commit eb6172a8ca7e0474457c1206c9907514348243ea
Showing with 65 additions and 36 deletions.
  1. +2 −1 src/init.cpp
  2. +2 −1 src/main.cpp
  3. +57 −34 src/script/sigcache.cpp
  4. +4 −0 src/script/sigcache.h
@@ -25,6 +25,7 @@
#include "policy/policy.h"
#include "rpcserver.h"
#include "script/standard.h"
#include "script/sigcache.h"
#include "scheduler.h"
#include "txdb.h"
#include "txmempool.h"
@@ -437,7 +438,7 @@ std::string HelpMessage(HelpMessageMode mode)
strUsage += HelpMessageOpt("-logtimemicros", strprintf("Add microsecond precision to debug timestamps (default: %u)", DEFAULT_LOGTIMEMICROS));
strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default: %u)", 15));
strUsage += HelpMessageOpt("-relaypriority", strprintf("Require high priority for relaying free or low-fee transactions (default: %u)", 1));
strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> entries (default: %u)", 50000));
strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> MiB (default: %u)", DEFAULT_MAX_SIG_CACHE_SIZE));
strUsage += HelpMessageOpt("-minrelaytxfee=<amt>", strprintf(_("Fees (in %s/kB) smaller than this are considered zero fee for relaying, mining and transaction creation (default: %s)"),
@@ -1851,7 +1851,8 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
nFees += view.GetValueIn(tx)-tx.GetValueOut();

std::vector<CScriptCheck> vChecks;
if (!CheckInputs(tx, state, view, fScriptChecks, flags, false, nScriptCheckThreads ? &vChecks : NULL))
bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, nScriptCheckThreads ? &vChecks : NULL))
return error("ConnectBlock(): CheckInputs on %s failed with %s",
tx.GetHash().ToString(), FormatStateMessage(state));
@@ -5,16 +5,29 @@

#include "sigcache.h"

#include "memusage.h"
#include "pubkey.h"
#include "random.h"
#include "uint256.h"
#include "util.h"

#include <boost/thread.hpp>
#include <boost/tuple/tuple_comparison.hpp>
#include <boost/unordered_set.hpp>

namespace {

* We're hashing a nonce into the entries themselves, so we don't need extra
* blinding in the set hash computation.
class CSignatureCacheHasher
size_t operator()(const uint256& key) const {
return key.GetCheapHash();

* Valid signature cache, to avoid doing expensive ECDSA signature checking
* twice for every transaction (once when accepted into memory pool, and
@@ -23,52 +36,54 @@ namespace {
class CSignatureCache
//! sigdata_type is (signature hash, signature, public key):
typedef boost::tuple<uint256, std::vector<unsigned char>, CPubKey> sigdata_type;
std::set< sigdata_type> setValid;
//! Entries are SHA256(nonce || signature hash || public key || signature):
uint256 nonce;
typedef boost::unordered_set<uint256, CSignatureCacheHasher> map_type;
map_type setValid;
boost::shared_mutex cs_sigcache;

GetRandBytes(nonce.begin(), 32);

ComputeEntry(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey)
CSHA256().Write(nonce.begin(), 32).Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());

Get(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
Get(const uint256& entry)
boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
return setValid.count(entry);

sigdata_type k(hash, vchSig, pubKey);
std::set<sigdata_type>::iterator mi = setValid.find(k);
if (mi != setValid.end())
return true;
return false;
void Erase(const uint256& entry)
boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);

void Set(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
void Set(const uint256& entry)
// DoS prevention: limit cache size to less than 10MB
// (~200 bytes per cache entry times 50,000 entries)
// Since there are a maximum of 20,000 signature operations per block
// 50,000 is a reasonable default.
int64_t nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
size_t nMaxCacheSize = GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
if (nMaxCacheSize <= 0) return;

boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);

while (static_cast<int64_t>(setValid.size()) > nMaxCacheSize)
while (memusage::DynamicUsage(setValid) > nMaxCacheSize)
// Evict a random entry. Random because that helps
// foil would-be DoS attackers who might try to pre-generate
// and re-use a set of valid signatures just-slightly-greater
// than our cache size.
uint256 randomHash = GetRandHash();
std::vector<unsigned char> unused;
std::set<sigdata_type>::iterator it =
setValid.lower_bound(sigdata_type(randomHash, unused, unused));
if (it == setValid.end())
it = setValid.begin();
map_type::size_type s = GetRand(setValid.bucket_count());
map_type::local_iterator it = setValid.begin(s);
if (it != setValid.end(s)) {

sigdata_type k(hash, vchSig, pubKey);

@@ -78,13 +93,21 @@ bool CachingTransactionSignatureChecker::VerifySignature(const std::vector<unsig
static CSignatureCache signatureCache;

if (signatureCache.Get(sighash, vchSig, pubkey))
uint256 entry;
signatureCache.ComputeEntry(entry, sighash, vchSig, pubkey);

if (signatureCache.Get(entry)) {
if (!store) {
return true;

if (!TransactionSignatureChecker::VerifySignature(vchSig, pubkey, sighash))
return false;

if (store)
signatureCache.Set(sighash, vchSig, pubkey);
if (store) {
return true;
@@ -10,6 +10,10 @@

#include <vector>

// DoS prevention: limit cache size to less than 40MB (over 500000
// entries on 64-bit systems).
static const unsigned int DEFAULT_MAX_SIG_CACHE_SIZE = 40;

class CPubKey;

class CachingTransactionSignatureChecker : public TransactionSignatureChecker

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