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 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
 465 #ifdef USE_SSSE3
 466 #include <immintrin.h>
 467
 468 extern "C" int sha256_use_ssse3();
 469 bool fUseSSSE3 = sha256_use_ssse3() != 0;
 470
 471 inline void copyrow_swap32(uint32_t *to, uint32_t *from)
 472 {
 473     if (!fUseSSSE3)
 474     {
 475         for (int i = 0; i < 4; i++)
 476             to[i] = __builtin_bswap32(from[i]);
 477     }
 478     else
 479     {
 480         __m128i mask = _mm_set_epi8(12, 13, 14, 15, 8, 9, 10, 11, 4, 5, 6, 7, 0, 1, 2, 3);
 481         _mm_storeu_si128((__m128i *)&to[0], _mm_shuffle_epi8(_mm_loadu_si128((__m128i *)&from[0]), mask));
 482     }
 483 }
 484 #else
 485 inline void copyrow_swap32(uint32_t *to, uint32_t *from)
 486 {
 487     for (int i = 0; i < 4; i++)
 488         to[i] = __builtin_bswap32(from[i]);
 489 }
 490 #endif
 491
 492 bool fUse4Way = sha256_use_4way() != 0;
 493
 494 class ScanMidstateWorker
 495 {
 496 public:
 497     ScanMidstateWorker()
 498     { }
 499     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 500         : kernel(kernel), nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 501     {
 502         solutions = vector<std::pair<uint256,uint32_t> >();
 503     }
 504
 505     void Do_4way()
 506     {
 507         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 508
 509         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 510         CBigNum bnTargetPerCoinDay;
 511         bnTargetPerCoinDay.SetCompact(nBits);
 512         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256();
 513
 514         uint32_t state1[4 * 8] __attribute__((aligned(16)));
 515         uint32_t state2[4 * 8] __attribute__((aligned(16)));
 516         uint32_t blocks1[4 * 16] __attribute__((aligned(16)));
 517         uint32_t blocks2[4 * 16] __attribute__((aligned(16)));
 518
 519         vector<uint32_t> vRow = vector<uint32_t>(4);
 520         uint32_t *pnKernel = (uint32_t *) kernel;
 521
 522         for(int i = 0; i < 7; i++)
 523         {
 524             fill(vRow.begin(), vRow.end(), pnKernel[i]);
 525             copyrow_swap32(&blocks1[i*4], &vRow[0]);
 526         }
 527
 528         memcpy(&blocks1[28], &block1_suffix_4way[0], 36*4);   // sha256 padding
 529         memcpy(&blocks2[32], &block2_suffix_4way[0], 32*4);
 530
 531         uint32_t nTimeStamps[4] = {0, 0, 0, 0};
 532         uint32_t nHashes[4] = {0, 0, 0, 0};
 533
 534         // Search forward in time from the given timestamp
 535         // Stopping search in case of shutting down
 536         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx +=4)
 537         {
 538             sha256_init_4way(state1);
 539             sha256_init_4way(state2);
 540
 541             nTimeStamps[0] = nTimeTx;
 542             nTimeStamps[1] = nTimeTx+1;
 543             nTimeStamps[2] = nTimeTx+2;
 544             nTimeStamps[3] = nTimeTx+3;
 545
 546             copyrow_swap32(&blocks1[24], &nTimeStamps[0]); // Kernel timestamps
 547             sha256_transform_4way(&state1[0], &blocks1[0], 0); // first hashing
 548             memcpy(&blocks2[0], &state1[0], 128);
 549             sha256_transform_4way(&state2[0], &blocks2[0], 0); // second hashing
 550             copyrow_swap32(&nHashes[0], &state2[28]);
 551
 552             for(int nResult = 0; nResult < 4; nResult++)
 553             {
 554                 if (nHashes[nResult] <= nMaxTarget32) // Possible hit
 555                 {
 556                     uint256 nHashProofOfStake = 0;
 557                     uint32_t *pnHashProofOfStake = (uint32_t *) &nHashProofOfStake;
 558
 559                     for (int i = 0; i < 7; i++)
 560                         pnHashProofOfStake[i] = __builtin_bswap32(state2[(i*4) + nResult]);
 561                     pnHashProofOfStake[7] = nHashes[nResult];
 562
 563                     CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeStamps[nResult]) / COIN / nOneDay;
 564                     CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 565
 566                     if (bnTargetProofOfStake >= CBigNum(nHashProofOfStake))
 567                         solutions.push_back(std::pair<uint256,uint32_t>(nHashProofOfStake, nTimeStamps[nResult]));
 568                 }
 569             }
 570         }
 571     }
 572
 573     void Do_generic()
 574     {
 575         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 576
 577         // Init new sha256 context and update it
 578         //   with first 24 bytes of kernel
 579         SHA256_CTX workerCtx;
 580         SHA256_Init(&workerCtx);
 581         SHA256_Update(&workerCtx, kernel, 8 + 16);
 582         SHA256_CTX ctx = workerCtx;
 583
 584         // Sha256 result buffer
 585         uint32_t hashProofOfStake[8];
 586
 587         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 588         CBigNum bnTargetPerCoinDay;
 589         bnTargetPerCoinDay.SetCompact(nBits);
 590
 591         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 592             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 593
 594         // Search forward in time from the given timestamp
 595         // Stopping search in case of shutting down
 596         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 597         {
 598             // Complete first hashing iteration
 599             uint256 hash1;
 600             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 601             SHA256_Final((unsigned char*)&hash1, &ctx);
 602
 603             // Restore context
 604             ctx = workerCtx;
 605
 606             // Finally, calculate kernel hash
 607             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 608
 609             // Skip if hash doesn't satisfy the maximum target
 610             if (hashProofOfStake[7] > nMaxTarget32)
 611                 continue;
 612
 613             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 614             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 615
 616             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 617                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 618         }
 619     }
 620
 621     void Do()
 622     {
 623         if (fUse4Way)
 624             Do_4way();
 625         else
 626             Do_generic();
 627     }
 628
 629     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 630     {
 631         return solutions;
 632     }
 633
 634 private:
 635     std::vector<std::pair<uint256,uint32_t> > solutions;
 636
 637     uint8_t *kernel;
 638     uint32_t nBits;
 639     uint32_t nInputTxTime;
 640     CBigNum  bnValueIn;
 641     uint32_t nIntervalBegin;
 642     uint32_t nIntervalEnd;
 643 };
 644
 645 #else
 646 class ScanMidstateWorker
 647 {
 648 public:
 649     ScanMidstateWorker()
 650     { }
 651     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 652         : nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 653     {
 654         // Init new sha256 context and update it
 655         //   with first 24 bytes of kernel
 656         SHA256_Init(&workerCtx);
 657         SHA256_Update(&workerCtx, kernel, 8 + 16);
 658         solutions = vector<std::pair<uint256,uint32_t> >();
 659     }
 660
 661     void Do()
 662     {
 663         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 664         SHA256_CTX ctx = workerCtx;
 665
 666         // Sha256 result buffer
 667         uint32_t hashProofOfStake[8];
 668
 669         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 670         CBigNum bnTargetPerCoinDay;
 671         bnTargetPerCoinDay.SetCompact(nBits);
 672
 673         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 674             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 675
 676         // Search forward in time from the given timestamp
 677         // Stopping search in case of shutting down
 678         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 679         {
 680             // Complete first hashing iteration
 681             uint256 hash1;
 682             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 683             SHA256_Final((unsigned char*)&hash1, &ctx);
 684
 685             // Restore context
 686             ctx = workerCtx;
 687
 688             // Finally, calculate kernel hash
 689             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 690
 691             // Skip if hash doesn't satisfy the maximum target
 692             if (hashProofOfStake[7] > nMaxTarget32)
 693                 continue;
 694
 695             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 696             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 697
 698             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 699                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 700         }
 701     }
 702
 703     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 704     {
 705         return solutions;
 706     }
 707
 708 private:
 709     SHA256_CTX workerCtx;
 710     std::vector<std::pair<uint256,uint32_t> > solutions;
 711
 712     uint32_t nBits;
 713     uint32_t nInputTxTime;
 714     CBigNum  bnValueIn;
 715     uint32_t nIntervalBegin;
 716     uint32_t nIntervalEnd;
 717 };
 718
 719 #endif
 720 // Scan given kernel for solution
 721 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)
 722 {
 723     // TODO: custom threads amount
 724
 725     uint32_t nThreads = boost::thread::hardware_concurrency();
 726     uint32_t nPart = (SearchInterval.second - SearchInterval.first) / nThreads;
 727
 728
 729     ScanMidstateWorker *workers = new ScanMidstateWorker[nThreads];
 730
 731     boost::thread_group group;
 732     for(size_t i = 0; i < nThreads; i++)
 733     {
 734         uint32_t nBegin = SearchInterval.first + nPart * i;
 735         uint32_t nEnd = SearchInterval.first + nPart * (i + 1);
 736         workers[i] = ScanMidstateWorker(kernel, nBits, nInputTxTime, nValueIn, nBegin, nEnd);
 737         boost::function<void()> workerFnc = boost::bind(&ScanMidstateWorker::Do, &workers[i]);
 738         group.create_thread(workerFnc);
 739     }
 740
 741     group.join_all();
 742     solutions.clear();
 743
 744     for(size_t i = 0; i < nThreads; i++)
 745     {
 746         std::vector<std::pair<uint256, uint32_t> > ws = workers[i].GetSolutions();
 747         solutions.insert(solutions.end(), ws.begin(), ws.end());
 748     }
 749
 750     delete [] workers;
 751
 752     if (solutions.size() == 0)
 753     {
 754         // no solutions
 755         return false;
 756     }
 757
 758     return true;
 759 }
 760
 761 // Scan given midstate for solution
 762 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)
 763 {
 764     CBigNum bnTargetPerCoinDay;
 765     bnTargetPerCoinDay.SetCompact(nBits);
 766
 767     // Get maximum possible target to filter out the majority of obviously insufficient hashes
 768     CBigNum bnMaxTargetPerCoinDay = bnTargetPerCoinDay * CBigNum(nValueIn) * nStakeMaxAge / COIN / nOneDay;
 769     uint256 maxTarget = bnMaxTargetPerCoinDay.getuint256();
 770
 771     SHA256_CTX ctxCopy = ctx;
 772
 773     // Search backward in time from the given timestamp
 774     // Stopping search in case of shutting down
 775     for (uint32_t nTimeTx=SearchInterval.first; nTimeTx>SearchInterval.second && !fShutdown; nTimeTx--)
 776     {
 777         // Complete first hashing iteration
 778         uint256 hash1;
 779         SHA256_Update(&ctxCopy, (unsigned char*)&nTimeTx, 4);
 780         SHA256_Final((unsigned char*)&hash1, &ctxCopy);
 781
 782         // Restore context
 783         ctxCopy = ctx;
 784
 785         // Finally, calculate kernel hash
 786         uint256 hashProofOfStake;
 787         SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 788
 789         // Skip if hash doesn't satisfy the maximum target
 790         if (hashProofOfStake > maxTarget)
 791             continue;
 792
 793         CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 794         CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 795
 796         if (bnTargetProofOfStake >= CBigNum(hashProofOfStake))
 797         {
 798             solution.first = hashProofOfStake;
 799             solution.second = nTimeTx;
 800
 801             return true;
 802         }
 803     }
 804
 805     return false;
 806 }
 807
 808 // Check kernel hash target and coinstake signature
 809 bool CheckProofOfStake(const CTransaction& tx, unsigned int nBits, uint256& hashProofOfStake, uint256& targetProofOfStake)
 810 {
 811     if (!tx.IsCoinStake())
 812         return error("CheckProofOfStake() : called on non-coinstake %s", tx.GetHash().ToString().c_str());
 813
 814     // Kernel (input 0) must match the stake hash target per coin age (nBits)
 815     const CTxIn& txin = tx.vin[0];
 816
 817     // First try finding the previous transaction in database
 818     CTxDB txdb("r");
 819     CTransaction txPrev;
 820     CTxIndex txindex;
 821     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
 822         return tx.DoS(1, error("CheckProofOfStake() : INFO: read txPrev failed"));  // previous transaction not in main chain, may occur during initial download
 823
 824 #ifndef USE_LEVELDB
 825     txdb.Close();
 826 #endif
 827
 828     // Verify signature
 829     if (!VerifySignature(txPrev, tx, 0, MANDATORY_SCRIPT_VERIFY_FLAGS, 0))
 830         return tx.DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", tx.GetHash().ToString().c_str()));
 831
 832     // Read block header
 833     CBlock block;
 834     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
 835         return fDebug? error("CheckProofOfStake() : read block failed") : false; // unable to read block of previous transaction
 836
 837     if (!CheckStakeKernelHash(nBits, block, txindex.pos.nTxPos - txindex.pos.nBlockPos, txPrev, txin.prevout, tx.nTime, hashProofOfStake, targetProofOfStake, fDebug))
 838         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
 839
 840     return true;
 841 }
 842
 843 // Get stake modifier checksum
 844 uint32_t GetStakeModifierChecksum(const CBlockIndex* pindex)
 845 {
 846     assert (pindex->pprev || pindex->GetBlockHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
 847     // Hash previous checksum with flags, hashProofOfStake and nStakeModifier
 848     CDataStream ss(SER_GETHASH, 0);
 849     if (pindex->pprev)
 850         ss << pindex->pprev->nStakeModifierChecksum;
 851     ss << pindex->nFlags << pindex->hashProofOfStake << pindex->nStakeModifier;
 852     uint256 hashChecksum = Hash(ss.begin(), ss.end());
 853     hashChecksum >>= (256 - 32);
 854     return static_cast<uint32_t>(hashChecksum.Get64());
 855 }
 856
 857 // Check stake modifier hard checkpoints
 858 bool CheckStakeModifierCheckpoints(int nHeight, uint32_t nStakeModifierChecksum)
 859 {
 860     MapModifierCheckpoints& checkpoints = (fTestNet ? mapStakeModifierCheckpointsTestNet : mapStakeModifierCheckpoints);
 861
 862     if (checkpoints.count(nHeight))
 863         return nStakeModifierChecksum == checkpoints[nHeight];
 864     return true;
 865 }