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, 0x000000e0 };
 434 static const uint32_t block1_suffix_4way[4 * 9] = {
 435     0x80000000, 0x80000000, 0x80000000, 0x80000000,
 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     0x000000e0, 0x000000e0, 0x000000e0, 0x000000e0
 444 };
 445
 446 // hash padding
 447 static const uint32_t block2_suffix[8] = { 0x80000000, 0, 0, 0, 0, 0, 0, 0x00000100 };
 448 static const uint32_t block2_suffix_4way[4 * 8] = {
 449     0x80000000, 0x80000000, 0x80000000, 0x80000000,
 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     0x00000100, 0x00000100, 0x00000100, 0x00000100
 457 };
 458
 459 // Sha256 initial state
 460 static const uint32_t sha256_initial[8] = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };
 461
 462 extern "C" int sha256_use_4way();
 463 extern "C" void sha256_init(uint32_t *state);
 464 extern "C" void sha256_transform(uint32_t *state, const uint32_t *block, int swap);
 465 extern "C" void sha256_init_4way(uint32_t *state);
 466 extern "C" void sha256_transform_4way(uint32_t *state, const uint32_t *block, int swap);
 467
 468 #ifdef USE_SSSE3
 469 #include <immintrin.h>
 470
 471 extern "C" int sha256_use_ssse3();
 472 bool fUseSSSE3 = sha256_use_ssse3() != 0;
 473
 474 inline void copyrow_swap32(uint32_t *to, uint32_t *from)
 475 {
 476     if (!fUseSSSE3)
 477     {
 478         for (int i = 0; i < 4; i++)
 479             to[i] = __builtin_bswap32(from[i]);
 480     }
 481     else
 482     {
 483         __m128i mask = _mm_set_epi8(12, 13, 14, 15, 8, 9, 10, 11, 4, 5, 6, 7, 0, 1, 2, 3);
 484         _mm_storeu_si128((__m128i *)&to[0], _mm_shuffle_epi8(_mm_loadu_si128((__m128i *)&from[0]), mask));
 485     }
 486 }
 487 #else
 488 inline void copyrow_swap32(uint32_t *to, uint32_t *from)
 489 {
 490     for (int i = 0; i < 4; i++)
 491         to[i] = __builtin_bswap32(from[i]);
 492 }
 493 #endif
 494
 495 bool fUse4Way = sha256_use_4way() != 0;
 496
 497 class ScanMidstateWorker
 498 {
 499 public:
 500     ScanMidstateWorker()
 501     { }
 502     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 503         : kernel(kernel), nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 504     {
 505         solutions = vector<std::pair<uint256,uint32_t> >();
 506     }
 507
 508     void Do_4way()
 509     {
 510         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 511
 512         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 513         CBigNum bnTargetPerCoinDay;
 514         bnTargetPerCoinDay.SetCompact(nBits);
 515         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256();
 516
 517         uint32_t blocks1[4 * 16] __attribute__((aligned(16)));
 518         uint32_t blocks2[4 * 16] __attribute__((aligned(16)));
 519         uint32_t candidates[4 * 8] __attribute__((aligned(16)));
 520
 521         vector<uint32_t> vRow = vector<uint32_t>(4);
 522         uint32_t *pnKernel = (uint32_t *) kernel;
 523
 524         for(int i = 0; i < 7; i++)
 525         {
 526             fill(vRow.begin(), vRow.end(), pnKernel[i]);
 527             copyrow_swap32(&blocks1[i*4], &vRow[0]);
 528         }
 529
 530         memcpy(&blocks1[28], &block1_suffix_4way[0], 36*4);   // sha256 padding
 531         memcpy(&blocks2[32], &block2_suffix_4way[0], 32*4);
 532
 533         uint32_t nTimeStamps[4] = {0, 0, 0, 0};
 534         uint32_t nHashes[4] = {0, 0, 0, 0};
 535
 536         // Search forward in time from the given timestamp
 537         // Stopping search in case of shutting down
 538         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx +=4)
 539         {
 540             sha256_init_4way(blocks2);
 541             sha256_init_4way(candidates);
 542
 543             nTimeStamps[0] = nTimeTx;
 544             nTimeStamps[1] = nTimeTx+1;
 545             nTimeStamps[2] = nTimeTx+2;
 546             nTimeStamps[3] = nTimeTx+3;
 547
 548             copyrow_swap32(&blocks1[24], &nTimeStamps[0]); // Kernel timestamps
 549
 550             sha256_transform_4way(&blocks2[0], &blocks1[0], 0); // first hashing
 551             sha256_transform_4way(&candidates[0], &blocks2[0], 0); // second hashing
 552             copyrow_swap32(&nHashes[0], &candidates[28]);
 553
 554             for(int nResult = 0; nResult < 4; nResult++)
 555             {
 556                 if (nHashes[nResult] <= nMaxTarget32) // Possible hit
 557                 {
 558                     uint256 nHashProofOfStake = 0;
 559                     uint32_t *pnHashProofOfStake = (uint32_t *) &nHashProofOfStake;
 560
 561                     for (int i = 0; i < 7; i++)
 562                         pnHashProofOfStake[i] = __builtin_bswap32(candidates[(i*4) + nResult]);
 563                     pnHashProofOfStake[7] = nHashes[nResult];
 564
 565                     CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeStamps[nResult]) / COIN / nOneDay;
 566                     CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 567
 568                     if (bnTargetProofOfStake >= CBigNum(nHashProofOfStake))
 569                         solutions.push_back(std::pair<uint256,uint32_t>(nHashProofOfStake, nTimeStamps[nResult]));
 570                 }
 571             }
 572         }
 573     }
 574
 575     void Do_oneway()
 576     {
 577         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 578
 579         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 580         CBigNum bnTargetPerCoinDay;
 581         bnTargetPerCoinDay.SetCompact(nBits);
 582         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256();
 583
 584         uint32_t block1[16] __attribute__((aligned(16)));
 585         uint32_t block2[16] __attribute__((aligned(16)));
 586         uint32_t candidate[8] __attribute__((aligned(16)));
 587
 588         memcpy(&block1[7], &block1_suffix[0], 36);   // sha256 padding
 589         memcpy(&block2[8], &block2_suffix[0], 32);
 590
 591         uint32_t *pnKernel = (uint32_t *) kernel;
 592         copyrow_swap32(&block1[0], pnKernel);
 593         block1[4] = __builtin_bswap32(pnKernel[4]);
 594         block1[5] = __builtin_bswap32(pnKernel[5]);
 595
 596         // Search forward in time from the given timestamp
 597         // Stopping search in case of shutting down
 598         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 599         {
 600             memcpy(&block2[0], &sha256_initial[0], 32);
 601             memcpy(&candidate[0], &sha256_initial[0], 32);
 602
 603             block1[6] = __builtin_bswap32(nTimeTx);
 604
 605             sha256_transform(&block2[0], &block1[0], 0); // first hashing
 606             sha256_transform(&candidate[0], &block2[0], 0); // second hashing
 607
 608             uint32_t nHash7 = __builtin_bswap32(candidate[7]);
 609
 610             // Skip if hash doesn't satisfy the maximum target
 611             if (nHash7 > nMaxTarget32)
 612                 continue;
 613
 614             uint256 nHashProofOfStake;
 615             uint32_t *pnHashProofOfStake = (uint32_t *) &nHashProofOfStake;
 616
 617             for (int i = 0; i < 7; i++)
 618                 pnHashProofOfStake[i] = __builtin_bswap32(candidate[i]);
 619             pnHashProofOfStake[7] = nHash7;
 620
 621             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 622             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 623
 624             if (bnTargetProofOfStake >= CBigNum(nHashProofOfStake))
 625                 solutions.push_back(std::pair<uint256,uint32_t>(nHashProofOfStake, nTimeTx));
 626         }
 627     }
 628
 629     void Do()
 630     {
 631         if (fUse4Way)
 632             Do_4way();
 633         else
 634             Do_oneway();
 635     }
 636
 637     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 638     {
 639         return solutions;
 640     }
 641
 642 private:
 643     std::vector<std::pair<uint256,uint32_t> > solutions;
 644
 645     uint8_t *kernel;
 646     uint32_t nBits;
 647     uint32_t nInputTxTime;
 648     CBigNum  bnValueIn;
 649     uint32_t nIntervalBegin;
 650     uint32_t nIntervalEnd;
 651 };
 652
 653 #else
 654 class ScanMidstateWorker
 655 {
 656 public:
 657     ScanMidstateWorker()
 658     { }
 659     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 660         : nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 661     {
 662         // Init new sha256 context and update it
 663         //   with first 24 bytes of kernel
 664         SHA256_Init(&workerCtx);
 665         SHA256_Update(&workerCtx, kernel, 8 + 16);
 666         solutions = vector<std::pair<uint256,uint32_t> >();
 667     }
 668
 669     void Do()
 670     {
 671         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 672         SHA256_CTX ctx = workerCtx;
 673
 674         // Sha256 result buffer
 675         uint32_t hashProofOfStake[8];
 676
 677         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 678         CBigNum bnTargetPerCoinDay;
 679         bnTargetPerCoinDay.SetCompact(nBits);
 680
 681         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 682             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 683
 684         // Search forward in time from the given timestamp
 685         // Stopping search in case of shutting down
 686         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 687         {
 688             // Complete first hashing iteration
 689             uint256 hash1;
 690             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 691             SHA256_Final((unsigned char*)&hash1, &ctx);
 692
 693             // Restore context
 694             ctx = workerCtx;
 695
 696             // Finally, calculate kernel hash
 697             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 698
 699             // Skip if hash doesn't satisfy the maximum target
 700             if (hashProofOfStake[7] > nMaxTarget32)
 701                 continue;
 702
 703             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 704             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 705
 706             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 707                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 708         }
 709     }
 710
 711     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 712     {
 713         return solutions;
 714     }
 715
 716 private:
 717     SHA256_CTX workerCtx;
 718     std::vector<std::pair<uint256,uint32_t> > solutions;
 719
 720     uint32_t nBits;
 721     uint32_t nInputTxTime;
 722     CBigNum  bnValueIn;
 723     uint32_t nIntervalBegin;
 724     uint32_t nIntervalEnd;
 725 };
 726
 727 #endif
 728 // Scan given kernel for solution
 729 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)
 730 {
 731     // TODO: custom threads amount
 732
 733     uint32_t nThreads = boost::thread::hardware_concurrency();
 734     uint32_t nPart = (SearchInterval.second - SearchInterval.first) / nThreads;
 735
 736
 737     ScanMidstateWorker *workers = new ScanMidstateWorker[nThreads];
 738
 739     boost::thread_group group;
 740     for(size_t i = 0; i < nThreads; i++)
 741     {
 742         uint32_t nBegin = SearchInterval.first + nPart * i;
 743         uint32_t nEnd = SearchInterval.first + nPart * (i + 1);
 744         workers[i] = ScanMidstateWorker(kernel, nBits, nInputTxTime, nValueIn, nBegin, nEnd);
 745         boost::function<void()> workerFnc = boost::bind(&ScanMidstateWorker::Do, &workers[i]);
 746         group.create_thread(workerFnc);
 747     }
 748
 749     group.join_all();
 750     solutions.clear();
 751
 752     for(size_t i = 0; i < nThreads; i++)
 753     {
 754         std::vector<std::pair<uint256, uint32_t> > ws = workers[i].GetSolutions();
 755         solutions.insert(solutions.end(), ws.begin(), ws.end());
 756     }
 757
 758     delete [] workers;
 759
 760     if (solutions.size() == 0)
 761     {
 762         // no solutions
 763         return false;
 764     }
 765
 766     return true;
 767 }
 768
 769 // Scan given midstate for solution
 770 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)
 771 {
 772     CBigNum bnTargetPerCoinDay;
 773     bnTargetPerCoinDay.SetCompact(nBits);
 774
 775     // Get maximum possible target to filter out the majority of obviously insufficient hashes
 776     CBigNum bnMaxTargetPerCoinDay = bnTargetPerCoinDay * CBigNum(nValueIn) * nStakeMaxAge / COIN / nOneDay;
 777     uint256 maxTarget = bnMaxTargetPerCoinDay.getuint256();
 778
 779     SHA256_CTX ctxCopy = ctx;
 780
 781     // Search backward in time from the given timestamp
 782     // Stopping search in case of shutting down
 783     for (uint32_t nTimeTx=SearchInterval.first; nTimeTx>SearchInterval.second && !fShutdown; nTimeTx--)
 784     {
 785         // Complete first hashing iteration
 786         uint256 hash1;
 787         SHA256_Update(&ctxCopy, (unsigned char*)&nTimeTx, 4);
 788         SHA256_Final((unsigned char*)&hash1, &ctxCopy);
 789
 790         // Restore context
 791         ctxCopy = ctx;
 792
 793         // Finally, calculate kernel hash
 794         uint256 hashProofOfStake;
 795         SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 796
 797         // Skip if hash doesn't satisfy the maximum target
 798         if (hashProofOfStake > maxTarget)
 799             continue;
 800
 801         CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 802         CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 803
 804         if (bnTargetProofOfStake >= CBigNum(hashProofOfStake))
 805         {
 806             solution.first = hashProofOfStake;
 807             solution.second = nTimeTx;
 808
 809             return true;
 810         }
 811     }
 812
 813     return false;
 814 }
 815
 816 // Check kernel hash target and coinstake signature
 817 bool CheckProofOfStake(const CTransaction& tx, unsigned int nBits, uint256& hashProofOfStake, uint256& targetProofOfStake)
 818 {
 819     if (!tx.IsCoinStake())
 820         return error("CheckProofOfStake() : called on non-coinstake %s", tx.GetHash().ToString().c_str());
 821
 822     // Kernel (input 0) must match the stake hash target per coin age (nBits)
 823     const CTxIn& txin = tx.vin[0];
 824
 825     // First try finding the previous transaction in database
 826     CTxDB txdb("r");
 827     CTransaction txPrev;
 828     CTxIndex txindex;
 829     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
 830         return tx.DoS(1, error("CheckProofOfStake() : INFO: read txPrev failed"));  // previous transaction not in main chain, may occur during initial download
 831
 832 #ifndef USE_LEVELDB
 833     txdb.Close();
 834 #endif
 835
 836     // Verify signature
 837     if (!VerifySignature(txPrev, tx, 0, MANDATORY_SCRIPT_VERIFY_FLAGS, 0))
 838         return tx.DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", tx.GetHash().ToString().c_str()));
 839
 840     // Read block header
 841     CBlock block;
 842     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
 843         return fDebug? error("CheckProofOfStake() : read block failed") : false; // unable to read block of previous transaction
 844
 845     if (!CheckStakeKernelHash(nBits, block, txindex.pos.nTxPos - txindex.pos.nBlockPos, txPrev, txin.prevout, tx.nTime, hashProofOfStake, targetProofOfStake, fDebug))
 846         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
 847
 848     return true;
 849 }
 850
 851 // Get stake modifier checksum
 852 uint32_t GetStakeModifierChecksum(const CBlockIndex* pindex)
 853 {
 854     assert (pindex->pprev || pindex->GetBlockHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
 855     // Hash previous checksum with flags, hashProofOfStake and nStakeModifier
 856     CDataStream ss(SER_GETHASH, 0);
 857     if (pindex->pprev)
 858         ss << pindex->pprev->nStakeModifierChecksum;
 859     ss << pindex->nFlags << pindex->hashProofOfStake << pindex->nStakeModifier;
 860     uint256 hashChecksum = Hash(ss.begin(), ss.end());
 861     hashChecksum >>= (256 - 32);
 862     return static_cast<uint32_t>(hashChecksum.Get64());
 863 }
 864
 865 // Check stake modifier hard checkpoints
 866 bool CheckStakeModifierCheckpoints(int nHeight, uint32_t nStakeModifierChecksum)
 867 {
 868     MapModifierCheckpoints& checkpoints = (fTestNet ? mapStakeModifierCheckpointsTestNet : mapStakeModifierCheckpoints);
 869
 870     if (checkpoints.count(nHeight))
 871         return nStakeModifierChecksum == checkpoints[nHeight];
 872     return true;
 873 }