src/kernel.cpp

   1 // Copyright (c) 2012-2013 The PPCoin developers
   2 // Copyright (c) 2013-2015 The Novacoin developers
   3 // Distributed under the MIT/X11 software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5 // Distributed under the MIT/X11 software license, see the accompanying
   6 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   7
   8 #include <boost/assign/list_of.hpp>
   9
  10 #include "kernel.h"
  11 #include "txdb.h"
  12
  13 extern unsigned int nStakeMaxAge;
  14 extern unsigned int nStakeTargetSpacing;
  15
  16 using namespace std;
  17
  18
  19 // Protocol switch time for fixed kernel modifier interval
  20 unsigned int nModifierSwitchTime  = 1413763200;    // Mon, 20 Oct 2014 00:00:00 GMT
  21 unsigned int nModifierTestSwitchTime = 1397520000; // Tue, 15 Apr 2014 00:00:00 GMT
  22
  23 // Note: user must upgrade before the protocol switch deadline, otherwise it's required to
  24 //   re-download the blockchain. The timestamp of upgrade is recorded in the blockchain
  25 //   database.
  26 unsigned int nModifierUpgradeTime = 0;
  27
  28 typedef std::map<int, unsigned int> MapModifierCheckpoints;
  29
  30 // Hard checkpoints of stake modifiers to ensure they are deterministic
  31 static std::map<int, unsigned int> mapStakeModifierCheckpoints =
  32     boost::assign::map_list_of
  33         ( 0, 0x0e00670bu )
  34         ( 12661, 0x5d84115du )
  35         (143990, 0x9c592c78u )
  36         (149000, 0x48f2bdc4u )
  37         (160000, 0x789df0f0u )
  38         (200000, 0x01ec1503u )
  39     ;
  40
  41 // Hard checkpoints of stake modifiers to ensure they are deterministic (testNet)
  42 static std::map<int, unsigned int> mapStakeModifierCheckpointsTestNet =
  43     boost::assign::map_list_of
  44         ( 0, 0x0e00670bu )
  45     ;
  46
  47 // Pregenerated entropy bits table (from genesis to #9689)
  48 //
  49 // Bits are packed into array of 256 bit integers:
  50 //
  51 // * array index calculated as nHeight / 256
  52 // * position of bit is calculated as nHeight & 0xFF.
  53 //
  54 const uint256 entropyStore[] = {
  55     uint256("0x4555b4dcc1d690ddd9b810c90c66e82b18bf4f43cc887246c418383ec120a5ab"),
  56     uint256("0xaa6d1198412fa77608addf6549c9198a22155e8afd7a9ded6179f6b7cfc66b0c"),
  57     uint256("0x9442fabfa4116fb14a9769c2eea003845a1f5c3a0260f36b497d68f3a3cd4078"),
  58     uint256("0x0e769042a9a98e42388195d699574b822d06515f7053ad884c53d7ee059f05b1"),
  59     uint256("0x7005aac20baf70251aebfe3f1b95987d83ef1e3e6963de8fed601d4dd07bf7cf"),
  60     uint256("0x58952c5c3de188f2e33c38d3f53d7bf44f9bc545a4289d266696273fa821be66"),
  61     uint256("0x50b6c2ed780c08aaec3f7665b1b6004206243e3866456fc910b83b52d07eeb63"),
  62     uint256("0x563841eefca85ba3384986c58100408ae3f1ba2ac727e1ac910ce154a06c702f"),
  63     uint256("0x79275b03938b3e27a9b01a7f7953c6c487c58355f5d4169accfbb800213ffd13"),
  64     uint256("0xd783f2538b3ed18f135af90adc687c5646d93aeaeaabc6667be94f7aa0a2d366"),
  65     uint256("0xb441d0c175c40c8e88b09d88ea008af79cbed2d28219427d2e72fda682974db8"),
  66     uint256("0x3204c43bd41f2e19628af3b0c9aca3db15bca4c8705d51056e7b17a319c04715"),
  67     uint256("0x7e80e6ab7857d8f2f261a0a49c783bd800b365b8c9b85cc0e13f73904b0dcaa9"),
  68     uint256("0xefaaee60ed82d2ad145c0e347941fdb131eb8fd289a45eef07121a93f283c5f1"),
  69     uint256("0x3efc86e4334da332c1fd4c12513c40cff689f3efdc7f9913230822adacdda4f9"),
  70     uint256("0xf0d6b8f38599a017fa35d1fbbf9ef51eca5ebc5b286aadba40c4c3e1d9bace0c"),
  71     uint256("0x286a67f27323486036a0a92d35382fc8963c0c00bad331723318b4b9fdb2b56e"),
  72     uint256("0xecbfaaa6567c54f08c4d5bd0118a2d7b58740f42cbfc73aa1536c1f5f76de87c"),
  73     uint256("0xf9a4de1c5c46520de5aaf10d3796cf0e27ddce98b3398357f5726a949664e308"),
  74     uint256("0xd75e6c4dc4be08401e3478d2467d9ab96a62af4f255c04a82c41af0de0a487bb"),
  75     uint256("0x1a82c3bc6ad6047294c16571b5e2b7316c97bf8813e7da15798b9820d67e39f2"),
  76     uint256("0xb49be0080de564e01829ded7e7971979565a741c5975dc9978dcc020192d396c"),
  77     uint256("0x0d8eed113be67663b5a15a0625a9b49792b5ea59c005c4f405914877acab7000"),
  78     uint256("0x8f9d46e2bc05a218ffa942965b747056197d393b097085523640cd59e07fe7c7"),
  79     uint256("0x7a63ab40bc7f40ac2ebe9ede438d97b45fa6ed6f8419016da8d5f7a670111dda"),
  80     uint256("0x63fbcc080448c43d6cf915c958314feff7a95a52ba43a68c05fc281d3a522d25"),
  81     uint256("0xf834cf824c326d3ea861ea1e85dc3289265e37045981e28208e7344a7f8081d7"),
  82     uint256("0xb4edc22ec98cc49b2f5af5bae3f52f5e6058280f74f2c432c2dd89ae49acceb8"),
  83     uint256("0x0fe596037dcf81bf5c64f39755261c404ed088af5c8c31dd7549b6657ee92365"),
  84     uint256("0xbbad51a0aeba254b01d18c328de9e932b9b859b61e622c325d64e2211b5e413d"),
  85     uint256("0xabf0194cc787be938bc51c7fdf1cae4ec79e65ebab8fa8b8f40541c44ef384b0"),
  86     uint256("0x83bc12d6fdbd3e854cb91c4ca7dfba3c38e8714121af88c8a8abdb33e5002438"),
  87     uint256("0x71a2513026cabaedcbe55aeb6dc8049e5b763a3f54f10c33dd333624f764b38c"),
  88     uint256("0xee6725632ff5c025dff6a18cd059875dcae20f399b03bccba13d9d5fcf6d9d9a"),
  89     uint256("0xa168a2741d1e7e50cc74b79f695c25ffd3576e6bd61353c2a20e569fd63b2dac"),
  90     uint256("0x6e462d2a87bfde9398b6747f94a8ed6a01e4d96c5b4372df5c910c106c48bd13"),
  91     uint256("0x8eeb696181957c4b22434028990f49cb30006827c73860e77e2eecf5c38be99d"),
  92     uint256("0x3188aaa65877b166f05cdc48f55b1f77a7d6fb221c395596d990ae5647e9ba96")
  93 };
  94
  95 // Whether the given block is subject to new modifier protocol
  96 bool IsFixedModifierInterval(unsigned int nTimeBlock)
  97 {
  98     return (nTimeBlock >= (fTestNet? nModifierTestSwitchTime : nModifierSwitchTime));
  99 }
 100
 101 // Get the last stake modifier and its generation time from a given block
 102 static bool GetLastStakeModifier(const CBlockIndex* pindex, uint64_t& nStakeModifier, int64_t& nModifierTime)
 103 {
 104     if (!pindex)
 105         return error("GetLastStakeModifier: null pindex");
 106     while (pindex && pindex->pprev && !pindex->GeneratedStakeModifier())
 107         pindex = pindex->pprev;
 108     if (!pindex->GeneratedStakeModifier())
 109         return error("GetLastStakeModifier: no generation at genesis block");
 110     nStakeModifier = pindex->nStakeModifier;
 111     nModifierTime = pindex->GetBlockTime();
 112     return true;
 113 }
 114
 115 // Get selection interval section (in seconds)
 116 static int64_t GetStakeModifierSelectionIntervalSection(int nSection)
 117 {
 118     assert (nSection >= 0 && nSection < 64);
 119     return (nModifierInterval * 63 / (63 + ((63 - nSection) * (MODIFIER_INTERVAL_RATIO - 1))));
 120 }
 121
 122 // Get stake modifier selection interval (in seconds)
 123 static int64_t GetStakeModifierSelectionInterval()
 124 {
 125     int64_t nSelectionInterval = 0;
 126     for (int nSection=0; nSection<64; nSection++)
 127         nSelectionInterval += GetStakeModifierSelectionIntervalSection(nSection);
 128     return nSelectionInterval;
 129 }
 130
 131 // select a block from the candidate blocks in vSortedByTimestamp, excluding
 132 // already selected blocks in vSelectedBlocks, and with timestamp up to
 133 // nSelectionIntervalStop.
 134 static bool SelectBlockFromCandidates(vector<pair<int64_t, uint256> >& vSortedByTimestamp, map<uint256, const CBlockIndex*>& mapSelectedBlocks,
 135     int64_t nSelectionIntervalStop, uint64_t nStakeModifierPrev, const CBlockIndex** pindexSelected)
 136 {
 137     bool fSelected = false;
 138     uint256 hashBest = 0;
 139     *pindexSelected = (const CBlockIndex*) 0;
 140     BOOST_FOREACH(const PAIRTYPE(int64_t, uint256)& item, vSortedByTimestamp)
 141     {
 142         if (!mapBlockIndex.count(item.second))
 143             return error("SelectBlockFromCandidates: failed to find block index for candidate block %s", item.second.ToString().c_str());
 144         const CBlockIndex* pindex = mapBlockIndex[item.second];
 145         if (fSelected && pindex->GetBlockTime() > nSelectionIntervalStop)
 146             break;
 147         if (mapSelectedBlocks.count(pindex->GetBlockHash()) > 0)
 148             continue;
 149         // compute the selection hash by hashing its proof-hash and the
 150         // previous proof-of-stake modifier
 151         uint256 hashProof = pindex->IsProofOfStake()? pindex->hashProofOfStake : pindex->GetBlockHash();
 152         CDataStream ss(SER_GETHASH, 0);
 153         ss << hashProof << nStakeModifierPrev;
 154         uint256 hashSelection = Hash(ss.begin(), ss.end());
 155         // the selection hash is divided by 2**32 so that proof-of-stake block
 156         // is always favored over proof-of-work block. this is to preserve
 157         // the energy efficiency property
 158         if (pindex->IsProofOfStake())
 159             hashSelection >>= 32;
 160         if (fSelected && hashSelection < hashBest)
 161         {
 162             hashBest = hashSelection;
 163             *pindexSelected = (const CBlockIndex*) pindex;
 164         }
 165         else if (!fSelected)
 166         {
 167             fSelected = true;
 168             hashBest = hashSelection;
 169             *pindexSelected = (const CBlockIndex*) pindex;
 170         }
 171     }
 172     if (fDebug && GetBoolArg("-printstakemodifier"))
 173         printf("SelectBlockFromCandidates: selection hash=%s\n", hashBest.ToString().c_str());
 174     return fSelected;
 175 }
 176
 177 // Stake Modifier (hash modifier of proof-of-stake):
 178 // The purpose of stake modifier is to prevent a txout (coin) owner from
 179 // computing future proof-of-stake generated by this txout at the time
 180 // of transaction confirmation. To meet kernel protocol, the txout
 181 // must hash with a future stake modifier to generate the proof.
 182 // Stake modifier consists of bits each of which is contributed from a
 183 // selected block of a given block group in the past.
 184 // The selection of a block is based on a hash of the block's proof-hash and
 185 // the previous stake modifier.
 186 // Stake modifier is recomputed at a fixed time interval instead of every
 187 // block. This is to make it difficult for an attacker to gain control of
 188 // additional bits in the stake modifier, even after generating a chain of
 189 // blocks.
 190 bool ComputeNextStakeModifier(const CBlockIndex* pindexCurrent, uint64_t& nStakeModifier, bool& fGeneratedStakeModifier)
 191 {
 192     nStakeModifier = 0;
 193     fGeneratedStakeModifier = false;
 194     const CBlockIndex* pindexPrev = pindexCurrent->pprev;
 195     if (!pindexPrev)
 196     {
 197         fGeneratedStakeModifier = true;
 198         return true;  // genesis block's modifier is 0
 199     }
 200
 201     // First find current stake modifier and its generation block time
 202     // if it's not old enough, return the same stake modifier
 203     int64_t nModifierTime = 0;
 204     if (!GetLastStakeModifier(pindexPrev, nStakeModifier, nModifierTime))
 205         return error("ComputeNextStakeModifier: unable to get last modifier");
 206     if (fDebug)
 207     {
 208         printf("ComputeNextStakeModifier: prev modifier=0x%016" PRIx64 " time=%s epoch=%u\n", nStakeModifier, DateTimeStrFormat(nModifierTime).c_str(), (unsigned int)nModifierTime);
 209     }
 210     if (nModifierTime / nModifierInterval >= pindexPrev->GetBlockTime() / nModifierInterval)
 211     {
 212         if (fDebug)
 213         {
 214             printf("ComputeNextStakeModifier: no new interval keep current modifier: pindexPrev nHeight=%d nTime=%u\n", pindexPrev->nHeight, (unsigned int)pindexPrev->GetBlockTime());
 215         }
 216         return true;
 217     }
 218     if (nModifierTime / nModifierInterval >= pindexCurrent->GetBlockTime() / nModifierInterval)
 219     {
 220         // fixed interval protocol requires current block timestamp also be in a different modifier interval
 221         if (IsFixedModifierInterval(pindexCurrent->nTime))
 222         {
 223             if (fDebug)
 224             {
 225                 printf("ComputeNextStakeModifier: no new interval keep current modifier: pindexCurrent nHeight=%d nTime=%u\n", pindexCurrent->nHeight, (unsigned int)pindexCurrent->GetBlockTime());
 226             }
 227             return true;
 228         }
 229         else
 230         {
 231             if (fDebug)
 232             {
 233                 printf("ComputeNextStakeModifier: old modifier at block %s not meeting fixed modifier interval: pindexCurrent nHeight=%d nTime=%u\n", pindexCurrent->GetBlockHash().ToString().c_str(), pindexCurrent->nHeight, (unsigned int)pindexCurrent->GetBlockTime());
 234             }
 235         }
 236     }
 237
 238     // Sort candidate blocks by timestamp
 239     vector<pair<int64_t, uint256> > vSortedByTimestamp;
 240     vSortedByTimestamp.reserve(64 * nModifierInterval / nStakeTargetSpacing);
 241     int64_t nSelectionInterval = GetStakeModifierSelectionInterval();
 242     int64_t nSelectionIntervalStart = (pindexPrev->GetBlockTime() / nModifierInterval) * nModifierInterval - nSelectionInterval;
 243     const CBlockIndex* pindex = pindexPrev;
 244     while (pindex && pindex->GetBlockTime() >= nSelectionIntervalStart)
 245     {
 246         vSortedByTimestamp.push_back(make_pair(pindex->GetBlockTime(), pindex->GetBlockHash()));
 247         pindex = pindex->pprev;
 248     }
 249     int nHeightFirstCandidate = pindex ? (pindex->nHeight + 1) : 0;
 250     reverse(vSortedByTimestamp.begin(), vSortedByTimestamp.end());
 251     sort(vSortedByTimestamp.begin(), vSortedByTimestamp.end());
 252
 253     // Select 64 blocks from candidate blocks to generate stake modifier
 254     uint64_t nStakeModifierNew = 0;
 255     int64_t nSelectionIntervalStop = nSelectionIntervalStart;
 256     map<uint256, const CBlockIndex*> mapSelectedBlocks;
 257     for (int nRound=0; nRound<min(64, (int)vSortedByTimestamp.size()); nRound++)
 258     {
 259         // add an interval section to the current selection round
 260         nSelectionIntervalStop += GetStakeModifierSelectionIntervalSection(nRound);
 261         // select a block from the candidates of current round
 262         if (!SelectBlockFromCandidates(vSortedByTimestamp, mapSelectedBlocks, nSelectionIntervalStop, nStakeModifier, &pindex))
 263             return error("ComputeNextStakeModifier: unable to select block at round %d", nRound);
 264         // write the entropy bit of the selected block
 265         nStakeModifierNew |= (((uint64_t)pindex->GetStakeEntropyBit()) << nRound);
 266         // add the selected block from candidates to selected list
 267         mapSelectedBlocks.insert(make_pair(pindex->GetBlockHash(), pindex));
 268         if (fDebug && GetBoolArg("-printstakemodifier"))
 269             printf("ComputeNextStakeModifier: selected round %d stop=%s height=%d bit=%d\n", nRound, DateTimeStrFormat(nSelectionIntervalStop).c_str(), pindex->nHeight, pindex->GetStakeEntropyBit());
 270     }
 271
 272     // Print selection map for visualization of the selected blocks
 273     if (fDebug && GetBoolArg("-printstakemodifier"))
 274     {
 275         string strSelectionMap = "";
 276         // '-' indicates proof-of-work blocks not selected
 277         strSelectionMap.insert(0, pindexPrev->nHeight - nHeightFirstCandidate + 1, '-');
 278         pindex = pindexPrev;
 279         while (pindex && pindex->nHeight >= nHeightFirstCandidate)
 280         {
 281             // '=' indicates proof-of-stake blocks not selected
 282             if (pindex->IsProofOfStake())
 283                 strSelectionMap.replace(pindex->nHeight - nHeightFirstCandidate, 1, "=");
 284             pindex = pindex->pprev;
 285         }
 286         BOOST_FOREACH(const PAIRTYPE(uint256, const CBlockIndex*)& item, mapSelectedBlocks)
 287         {
 288             // 'S' indicates selected proof-of-stake blocks
 289             // 'W' indicates selected proof-of-work blocks
 290             strSelectionMap.replace(item.second->nHeight - nHeightFirstCandidate, 1, item.second->IsProofOfStake()? "S" : "W");
 291         }
 292         printf("ComputeNextStakeModifier: selection height [%d, %d] map %s\n", nHeightFirstCandidate, pindexPrev->nHeight, strSelectionMap.c_str());
 293     }
 294     if (fDebug)
 295     {
 296         printf("ComputeNextStakeModifier: new modifier=0x%016" PRIx64 " time=%s\n", nStakeModifierNew, DateTimeStrFormat(pindexPrev->GetBlockTime()).c_str());
 297     }
 298
 299     nStakeModifier = nStakeModifierNew;
 300     fGeneratedStakeModifier = true;
 301     return true;
 302 }
 303
 304 // The stake modifier used to hash for a stake kernel is chosen as the stake
 305 // modifier about a selection interval later than the coin generating the kernel
 306 static bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64_t& nStakeModifier, int& nStakeModifierHeight, int64_t& nStakeModifierTime, bool fPrintProofOfStake)
 307 {
 308     nStakeModifier = 0;
 309     if (!mapBlockIndex.count(hashBlockFrom))
 310         return error("GetKernelStakeModifier() : block not indexed");
 311     const CBlockIndex* pindexFrom = mapBlockIndex[hashBlockFrom];
 312     nStakeModifierHeight = pindexFrom->nHeight;
 313     nStakeModifierTime = pindexFrom->GetBlockTime();
 314     int64_t nStakeModifierSelectionInterval = GetStakeModifierSelectionInterval();
 315     const CBlockIndex* pindex = pindexFrom;
 316     // loop to find the stake modifier later by a selection interval
 317     while (nStakeModifierTime < pindexFrom->GetBlockTime() + nStakeModifierSelectionInterval)
 318     {
 319         if (!pindex->pnext)
 320         {   // reached best block; may happen if node is behind on block chain
 321             if (fPrintProofOfStake || (pindex->GetBlockTime() + nStakeMinAge - nStakeModifierSelectionInterval > GetAdjustedTime()))
 322                 return error("GetKernelStakeModifier() : reached best block %s at height %d from block %s",
 323                     pindex->GetBlockHash().ToString().c_str(), pindex->nHeight, hashBlockFrom.ToString().c_str());
 324             else
 325                 return false;
 326         }
 327         pindex = pindex->pnext;
 328         if (pindex->GeneratedStakeModifier())
 329         {
 330             nStakeModifierHeight = pindex->nHeight;
 331             nStakeModifierTime = pindex->GetBlockTime();
 332         }
 333     }
 334     nStakeModifier = pindex->nStakeModifier;
 335     return true;
 336 }
 337
 338 bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64_t& nStakeModifier)
 339 {
 340     int nStakeModifierHeight;
 341     int64_t nStakeModifierTime;
 342
 343     return GetKernelStakeModifier(hashBlockFrom, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, false);
 344 }
 345
 346
 347 // ppcoin kernel protocol
 348 // coinstake must meet hash target according to the protocol:
 349 // kernel (input 0) must meet the formula
 350 //     hash(nStakeModifier + txPrev.block.nTime + txPrev.offset + txPrev.nTime + txPrev.vout.n + nTime) < bnTarget * nCoinDayWeight
 351 // this ensures that the chance of getting a coinstake is proportional to the
 352 // amount of coin age one owns.
 353 // The reason this hash is chosen is the following:
 354 //   nStakeModifier: scrambles computation to make it very difficult to precompute
 355 //                  future proof-of-stake at the time of the coin's confirmation
 356 //   txPrev.block.nTime: prevent nodes from guessing a good timestamp to
 357 //                       generate transaction for future advantage
 358 //   txPrev.offset: offset of txPrev inside block, to reduce the chance of
 359 //                  nodes generating coinstake at the same time
 360 //   txPrev.nTime: reduce the chance of nodes generating coinstake at the same
 361 //                 time
 362 //   txPrev.vout.n: output number of txPrev, to reduce the chance of nodes
 363 //                  generating coinstake at the same time
 364 //   block/tx hash should not be used here as they can be generated in vast
 365 //   quantities so as to generate blocks faster, degrading the system back into
 366 //   a proof-of-work situation.
 367 //
 368 bool CheckStakeKernelHash(uint32_t nBits, const CBlock& blockFrom, uint32_t nTxPrevOffset, const CTransaction& txPrev, const COutPoint& prevout, uint32_t nTimeTx, uint256& hashProofOfStake, uint256& targetProofOfStake, bool fPrintProofOfStake)
 369 {
 370     if (nTimeTx < txPrev.nTime)  // Transaction timestamp violation
 371         return error("CheckStakeKernelHash() : nTime violation");
 372
 373     uint32_t nTimeBlockFrom = blockFrom.GetBlockTime();
 374     if (nTimeBlockFrom + nStakeMinAge > nTimeTx) // Min age requirement
 375         return error("CheckStakeKernelHash() : min age violation");
 376
 377     CBigNum bnTargetPerCoinDay;
 378     bnTargetPerCoinDay.SetCompact(nBits);
 379     int64_t nValueIn = txPrev.vout[prevout.n].nValue;
 380
 381     uint256 hashBlockFrom = blockFrom.GetHash();
 382
 383     CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)txPrev.nTime, (int64_t)nTimeTx) / COIN / nOneDay;
 384     targetProofOfStake = (bnCoinDayWeight * bnTargetPerCoinDay).getuint256();
 385
 386     // Calculate hash
 387     CDataStream ss(SER_GETHASH, 0);
 388     uint64_t nStakeModifier = 0;
 389     int nStakeModifierHeight = 0;
 390     int64_t nStakeModifierTime = 0;
 391
 392     if (!GetKernelStakeModifier(hashBlockFrom, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake))
 393         return false;
 394     ss << nStakeModifier;
 395
 396     ss << nTimeBlockFrom << nTxPrevOffset << txPrev.nTime << prevout.n << nTimeTx;
 397     hashProofOfStake = Hash(ss.begin(), ss.end());
 398     if (fPrintProofOfStake)
 399     {
 400         printf("CheckStakeKernelHash() : using modifier 0x%016" PRIx64 " at height=%d timestamp=%s for block from height=%d timestamp=%s\n",
 401             nStakeModifier, nStakeModifierHeight,
 402             DateTimeStrFormat(nStakeModifierTime).c_str(),
 403             mapBlockIndex[hashBlockFrom]->nHeight,
 404             DateTimeStrFormat(blockFrom.GetBlockTime()).c_str());
 405         printf("CheckStakeKernelHash() : check modifier=0x%016" PRIx64 " nTimeBlockFrom=%u nTxPrevOffset=%u nTimeTxPrev=%u nPrevout=%u nTimeTx=%u hashTarget=%s hashProof=%s\n",
 406             nStakeModifier,
 407             nTimeBlockFrom, nTxPrevOffset, txPrev.nTime, prevout.n, nTimeTx,
 408             targetProofOfStake.ToString().c_str(), hashProofOfStake.ToString().c_str());
 409     }
 410
 411     // Now check if proof-of-stake hash meets target protocol
 412     if (CBigNum(hashProofOfStake) > bnCoinDayWeight * bnTargetPerCoinDay)
 413         return false;
 414     if (fDebug && !fPrintProofOfStake)
 415     {
 416         printf("CheckStakeKernelHash() : using modifier 0x%016" PRIx64 " at height=%d timestamp=%s for block from height=%d timestamp=%s\n",
 417             nStakeModifier, nStakeModifierHeight,
 418             DateTimeStrFormat(nStakeModifierTime).c_str(),
 419             mapBlockIndex[hashBlockFrom]->nHeight,
 420             DateTimeStrFormat(blockFrom.GetBlockTime()).c_str());
 421         printf("CheckStakeKernelHash() : pass modifier=0x%016" PRIx64 " nTimeBlockFrom=%u nTxPrevOffset=%u nTimeTxPrev=%u nPrevout=%u nTimeTx=%u hashTarget=%s hashProof=%s\n",
 422             nStakeModifier,
 423             nTimeBlockFrom, nTxPrevOffset, txPrev.nTime, prevout.n, nTimeTx,
 424             targetProofOfStake.ToString().c_str(), hashProofOfStake.ToString().c_str());
 425     }
 426     return true;
 427 }
 428
 429
 430 #ifdef USE_ASM
 431
 432 // kernel padding
 433 static const uint32_t block1_suffix[9] = { 0x80000000, 0, 0, 0, 0, 0, 0, 0, 0xe0000000 };
 434 static const uint32_t block1_suffix_4way[4 * 9] = {
 435     0x00000080, 0x00000080, 0x00000080, 0x00000080,
 436     0, 0, 0, 0,
 437     0, 0, 0, 0,
 438     0, 0, 0, 0,
 439     0, 0, 0, 0,
 440     0, 0, 0, 0,
 441     0, 0, 0, 0,
 442     0, 0, 0, 0,
 443     0xe0000000, 0xe0000000, 0xe0000000, 0xe0000000
 444 };
 445
 446 // hash padding
 447 static const uint32_t block2_suffix[8] = { 0x80000000, 0, 0, 0, 0, 0, 0, 0x00010000 };
 448 static const uint32_t block2_suffix_4way[4 * 8] = {
 449     0x00000080, 0x00000080, 0x00000080, 0x00000080,
 450     0, 0, 0, 0,
 451     0, 0, 0, 0,
 452     0, 0, 0, 0,
 453     0, 0, 0, 0,
 454     0, 0, 0, 0,
 455     0, 0, 0, 0,
 456     0x00010000, 0x00010000, 0x00010000, 0x00010000
 457 };
 458
 459 extern "C" int sha256_use_4way();
 460 extern "C" void sha256_init(uint32_t *state);
 461 extern "C" void sha256_transform(uint32_t *state, const uint32_t *block, int swap);
 462 extern "C" void sha256_init_4way(uint32_t *state);
 463 extern "C" void sha256_transform_4way(uint32_t *state, const uint32_t *block, int swap);
 464 extern "C" void copy_swap_hashes(uint32_t *blocks, uint32_t *state); // Generic block copy function
 465
 466 #ifdef USE_SSSE3
 467 extern "C" int sha256_use_ssse3();
 468 extern "C" void copy_swap_hashes_ssse3(uint32_t *blocks, uint32_t *state); // SSSE3 optimized block copy function
 469
 470 void (*copy_swap)(uint32_t *, uint32_t *) = (sha256_use_ssse3() != 0) ? &copy_swap_hashes_ssse3 : copy_swap_hashes;
 471 #else
 472 void (*copy_swap)(uint32_t *, uint32_t *) = &copy_swap_hashes;
 473 #endif
 474
 475 bool fUse4Way = sha256_use_4way() != 0;
 476
 477 class ScanMidstateWorker
 478 {
 479 public:
 480     ScanMidstateWorker()
 481     { }
 482     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 483         : kernel(kernel), nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 484     {
 485         solutions = vector<std::pair<uint256,uint32_t> >();
 486     }
 487
 488     void Do_4way()
 489     {
 490         cout << sha256_use_ssse3() << endl;
 491
 492         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 493
 494         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 495         CBigNum bnTargetPerCoinDay;
 496         bnTargetPerCoinDay.SetCompact(nBits);
 497         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256();
 498
 499         uint32_t state1[4 * 8] __attribute__((aligned(16)));
 500         uint32_t state2[4 * 8] __attribute__((aligned(16)));
 501         uint32_t blocks1[4 * 16] __attribute__((aligned(16)));
 502         uint32_t blocks2[4 * 16] __attribute__((aligned(16)));
 503
 504         vector<uint32_t> vRow = vector<uint32_t>(4);
 505         uint32_t *pnKernel = (uint32_t *) kernel;
 506
 507         for(int i = 0; i < 7; i++)
 508         {
 509             uint32_t nVal = pnKernel[i];
 510             fill(vRow.begin(), vRow.end(), nVal);
 511
 512             for (int j = 0; j < 4; j++)
 513             {
 514                 memcpy(&blocks1[i*4], &vRow[0], 16);
 515             }
 516         }
 517
 518         memcpy(&blocks1[28], &block1_suffix_4way[0], 36*4);   // sha256 padding
 519         memcpy(&blocks2[32], &block2_suffix_4way[0], 32*4);
 520
 521         // Search forward in time from the given timestamp
 522         // Stopping search in case of shutting down
 523         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; )
 524         {
 525             sha256_init_4way(state1);
 526             sha256_init_4way(state2);
 527
 528             blocks1[24] = nTimeTx++;
 529             blocks1[25] = nTimeTx++;
 530             blocks1[26] = nTimeTx++;
 531             blocks1[27] = nTimeTx++;
 532
 533             sha256_transform_4way(&state1[0], &blocks1[0], 1); // first hashing
 534             copy_swap(&blocks2[0], &state1[0]);
 535             sha256_transform_4way(&state2[0], &blocks2[0], 1); // second hashing
 536
 537             for(int nResult = 0; nResult < 4; nResult++)
 538             {
 539                 uint32_t nHash = __builtin_bswap32(state2[28+nResult]);
 540
 541                 if (nHash <= nMaxTarget32) // Possible hit
 542                 {
 543                     uint32_t nTime = blocks1[24+nResult];
 544                     uint256 nHashProofOfStake = 0;
 545                     uint32_t *pnHashProofOfStake = (uint32_t *) &nHashProofOfStake;
 546                     pnHashProofOfStake[7] = nHash;
 547
 548                     for (int i = 0; i < 7; i++)
 549                         pnHashProofOfStake[i] = __builtin_bswap32(state2[(i*4) + nResult]);
 550
 551                     CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 552                     CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 553
 554                     if (bnTargetProofOfStake >= CBigNum(nHashProofOfStake))
 555                         solutions.push_back(std::pair<uint256,uint32_t>(nHashProofOfStake, nTime));
 556                 }
 557             }
 558         }
 559     }
 560
 561     void Do_generic()
 562     {
 563         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 564
 565         // Init new sha256 context and update it
 566         //   with first 24 bytes of kernel
 567         SHA256_CTX workerCtx;
 568         SHA256_Init(&workerCtx);
 569         SHA256_Update(&workerCtx, kernel, 8 + 16);
 570         SHA256_CTX ctx = workerCtx;
 571
 572         // Sha256 result buffer
 573         uint32_t hashProofOfStake[8];
 574
 575         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 576         CBigNum bnTargetPerCoinDay;
 577         bnTargetPerCoinDay.SetCompact(nBits);
 578
 579         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 580             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 581
 582         // Search forward in time from the given timestamp
 583         // Stopping search in case of shutting down
 584         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 585         {
 586             // Complete first hashing iteration
 587             uint256 hash1;
 588             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 589             SHA256_Final((unsigned char*)&hash1, &ctx);
 590
 591             // Restore context
 592             ctx = workerCtx;
 593
 594             // Finally, calculate kernel hash
 595             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 596
 597             // Skip if hash doesn't satisfy the maximum target
 598             if (hashProofOfStake[7] > nMaxTarget32)
 599                 continue;
 600
 601             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 602             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 603
 604             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 605                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 606         }
 607     }
 608
 609     void Do()
 610     {
 611         if (fUse4Way)
 612             Do_4way();
 613         else
 614             Do_generic();
 615     }
 616
 617     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 618     {
 619         return solutions;
 620     }
 621
 622 private:
 623     std::vector<std::pair<uint256,uint32_t> > solutions;
 624
 625     uint8_t *kernel;
 626     uint32_t nBits;
 627     uint32_t nInputTxTime;
 628     CBigNum  bnValueIn;
 629     uint32_t nIntervalBegin;
 630     uint32_t nIntervalEnd;
 631 };
 632
 633 #else
 634 class ScanMidstateWorker
 635 {
 636 public:
 637     ScanMidstateWorker()
 638     { }
 639     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 640         : nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 641     {
 642         // Init new sha256 context and update it
 643         //   with first 24 bytes of kernel
 644         SHA256_Init(&workerCtx);
 645         SHA256_Update(&workerCtx, kernel, 8 + 16);
 646         solutions = vector<std::pair<uint256,uint32_t> >();
 647     }
 648
 649     void Do()
 650     {
 651         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 652         SHA256_CTX ctx = workerCtx;
 653
 654         // Sha256 result buffer
 655         uint32_t hashProofOfStake[8];
 656
 657         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 658         CBigNum bnTargetPerCoinDay;
 659         bnTargetPerCoinDay.SetCompact(nBits);
 660
 661         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 662             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 663
 664         // Search forward in time from the given timestamp
 665         // Stopping search in case of shutting down
 666         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 667         {
 668             // Complete first hashing iteration
 669             uint256 hash1;
 670             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 671             SHA256_Final((unsigned char*)&hash1, &ctx);
 672
 673             // Restore context
 674             ctx = workerCtx;
 675
 676             // Finally, calculate kernel hash
 677             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 678
 679             // Skip if hash doesn't satisfy the maximum target
 680             if (hashProofOfStake[7] > nMaxTarget32)
 681                 continue;
 682
 683             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 684             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 685
 686             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 687                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 688         }
 689     }
 690
 691     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 692     {
 693         return solutions;
 694     }
 695
 696 private:
 697     SHA256_CTX workerCtx;
 698     std::vector<std::pair<uint256,uint32_t> > solutions;
 699
 700     uint32_t nBits;
 701     uint32_t nInputTxTime;
 702     CBigNum  bnValueIn;
 703     uint32_t nIntervalBegin;
 704     uint32_t nIntervalEnd;
 705 };
 706
 707 #endif
 708 // Scan given kernel for solution
 709 bool ScanKernelForward(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, std::pair<uint32_t, uint32_t> &SearchInterval, std::vector<std::pair<uint256, uint32_t> > &solutions)
 710 {
 711     // TODO: custom threads amount
 712
 713     uint32_t nThreads = boost::thread::hardware_concurrency();
 714     uint32_t nPart = (SearchInterval.second - SearchInterval.first) / nThreads;
 715
 716
 717     ScanMidstateWorker *workers = new ScanMidstateWorker[nThreads];
 718
 719     boost::thread_group group;
 720     for(size_t i = 0; i < nThreads; i++)
 721     {
 722         uint32_t nBegin = SearchInterval.first + nPart * i;
 723         uint32_t nEnd = SearchInterval.first + nPart * (i + 1);
 724         workers[i] = ScanMidstateWorker(kernel, nBits, nInputTxTime, nValueIn, nBegin, nEnd);
 725         boost::function<void()> workerFnc = boost::bind(&ScanMidstateWorker::Do, &workers[i]);
 726         group.create_thread(workerFnc);
 727     }
 728
 729     group.join_all();
 730     solutions.clear();
 731
 732     for(size_t i = 0; i < nThreads; i++)
 733     {
 734         std::vector<std::pair<uint256, uint32_t> > ws = workers[i].GetSolutions();
 735         solutions.insert(solutions.end(), ws.begin(), ws.end());
 736     }
 737
 738     delete [] workers;
 739
 740     if (solutions.size() == 0)
 741     {
 742         // no solutions
 743         return false;
 744     }
 745
 746     return true;
 747 }
 748
 749 // Scan given midstate for solution
 750 bool ScanContextBackward(SHA256_CTX &ctx, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, std::pair<uint32_t, uint32_t> &SearchInterval, std::pair<uint256, uint32_t> &solution)
 751 {
 752     CBigNum bnTargetPerCoinDay;
 753     bnTargetPerCoinDay.SetCompact(nBits);
 754
 755     // Get maximum possible target to filter out the majority of obviously insufficient hashes
 756     CBigNum bnMaxTargetPerCoinDay = bnTargetPerCoinDay * CBigNum(nValueIn) * nStakeMaxAge / COIN / nOneDay;
 757     uint256 maxTarget = bnMaxTargetPerCoinDay.getuint256();
 758
 759     SHA256_CTX ctxCopy = ctx;
 760
 761     // Search backward in time from the given timestamp
 762     // Stopping search in case of shutting down
 763     for (uint32_t nTimeTx=SearchInterval.first; nTimeTx>SearchInterval.second && !fShutdown; nTimeTx--)
 764     {
 765         // Complete first hashing iteration
 766         uint256 hash1;
 767         SHA256_Update(&ctxCopy, (unsigned char*)&nTimeTx, 4);
 768         SHA256_Final((unsigned char*)&hash1, &ctxCopy);
 769
 770         // Restore context
 771         ctxCopy = ctx;
 772
 773         // Finally, calculate kernel hash
 774         uint256 hashProofOfStake;
 775         SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 776
 777         // Skip if hash doesn't satisfy the maximum target
 778         if (hashProofOfStake > maxTarget)
 779             continue;
 780
 781         CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 782         CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 783
 784         if (bnTargetProofOfStake >= CBigNum(hashProofOfStake))
 785         {
 786             solution.first = hashProofOfStake;
 787             solution.second = nTimeTx;
 788
 789             return true;
 790         }
 791     }
 792
 793     return false;
 794 }
 795
 796 // Check kernel hash target and coinstake signature
 797 bool CheckProofOfStake(const CTransaction& tx, unsigned int nBits, uint256& hashProofOfStake, uint256& targetProofOfStake)
 798 {
 799     if (!tx.IsCoinStake())
 800         return error("CheckProofOfStake() : called on non-coinstake %s", tx.GetHash().ToString().c_str());
 801
 802     // Kernel (input 0) must match the stake hash target per coin age (nBits)
 803     const CTxIn& txin = tx.vin[0];
 804
 805     // First try finding the previous transaction in database
 806     CTxDB txdb("r");
 807     CTransaction txPrev;
 808     CTxIndex txindex;
 809     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
 810         return tx.DoS(1, error("CheckProofOfStake() : INFO: read txPrev failed"));  // previous transaction not in main chain, may occur during initial download
 811
 812 #ifndef USE_LEVELDB
 813     txdb.Close();
 814 #endif
 815
 816     // Verify signature
 817     if (!VerifySignature(txPrev, tx, 0, MANDATORY_SCRIPT_VERIFY_FLAGS, 0))
 818         return tx.DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", tx.GetHash().ToString().c_str()));
 819
 820     // Read block header
 821     CBlock block;
 822     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
 823         return fDebug? error("CheckProofOfStake() : read block failed") : false; // unable to read block of previous transaction
 824
 825     if (!CheckStakeKernelHash(nBits, block, txindex.pos.nTxPos - txindex.pos.nBlockPos, txPrev, txin.prevout, tx.nTime, hashProofOfStake, targetProofOfStake, fDebug))
 826         return tx.DoS(1, error("CheckProofOfStake() : INFO: check kernel failed on coinstake %s, hashProof=%s", tx.GetHash().ToString().c_str(), hashProofOfStake.ToString().c_str())); // may occur during initial download or if behind on block chain sync
 827
 828     return true;
 829 }
 830
 831 // Get stake modifier checksum
 832 uint32_t GetStakeModifierChecksum(const CBlockIndex* pindex)
 833 {
 834     assert (pindex->pprev || pindex->GetBlockHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
 835     // Hash previous checksum with flags, hashProofOfStake and nStakeModifier
 836     CDataStream ss(SER_GETHASH, 0);
 837     if (pindex->pprev)
 838         ss << pindex->pprev->nStakeModifierChecksum;
 839     ss << pindex->nFlags << pindex->hashProofOfStake << pindex->nStakeModifier;
 840     uint256 hashChecksum = Hash(ss.begin(), ss.end());
 841     hashChecksum >>= (256 - 32);
 842     return static_cast<uint32_t>(hashChecksum.Get64());
 843 }
 844
 845 // Check stake modifier hard checkpoints
 846 bool CheckStakeModifierCheckpoints(int nHeight, uint32_t nStakeModifierChecksum)
 847 {
 848     MapModifierCheckpoints& checkpoints = (fTestNet ? mapStakeModifierCheckpointsTestNet : mapStakeModifierCheckpoints);
 849
 850     if (checkpoints.count(nHeight))
 851         return nStakeModifierChecksum == checkpoints[nHeight];
 852     return true;
 853 }