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         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 491
 492         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 493         CBigNum bnTargetPerCoinDay;
 494         bnTargetPerCoinDay.SetCompact(nBits);
 495         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256();
 496
 497         uint32_t state1[4 * 8] __attribute__((aligned(16)));
 498         uint32_t state2[4 * 8] __attribute__((aligned(16)));
 499         uint32_t blocks1[4 * 16] __attribute__((aligned(16)));
 500         uint32_t blocks2[4 * 16] __attribute__((aligned(16)));
 501
 502         vector<uint32_t> vRow = vector<uint32_t>(4);
 503         uint32_t *pnKernel = (uint32_t *) kernel;
 504
 505         for(int i = 0; i < 7; i++)
 506         {
 507             uint32_t nVal = pnKernel[i];
 508             fill(vRow.begin(), vRow.end(), nVal);
 509
 510             for (int j = 0; j < 4; j++)
 511             {
 512                 memcpy(&blocks1[i*4], &vRow[0], 16);
 513             }
 514         }
 515
 516         memcpy(&blocks1[28], &block1_suffix_4way[0], 36*4);   // sha256 padding
 517         memcpy(&blocks2[32], &block2_suffix_4way[0], 32*4);
 518
 519         // Search forward in time from the given timestamp
 520         // Stopping search in case of shutting down
 521         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; )
 522         {
 523             sha256_init_4way(state1);
 524             sha256_init_4way(state2);
 525
 526             blocks1[24] = nTimeTx++;
 527             blocks1[25] = nTimeTx++;
 528             blocks1[26] = nTimeTx++;
 529             blocks1[27] = nTimeTx++;
 530
 531             sha256_transform_4way(&state1[0], &blocks1[0], 1); // first hashing
 532             copy_swap(&blocks2[0], &state1[0]);
 533             sha256_transform_4way(&state2[0], &blocks2[0], 1); // second hashing
 534
 535             for(int nResult = 0; nResult < 4; nResult++)
 536             {
 537                 uint32_t nHash = __builtin_bswap32(state2[28+nResult]);
 538
 539                 if (nHash <= nMaxTarget32) // Possible hit
 540                 {
 541                     uint32_t nTime = blocks1[24+nResult];
 542                     uint256 nHashProofOfStake = 0;
 543                     uint32_t *pnHashProofOfStake = (uint32_t *) &nHashProofOfStake;
 544                     pnHashProofOfStake[7] = nHash;
 545
 546                     for (int i = 0; i < 7; i++)
 547                         pnHashProofOfStake[i] = __builtin_bswap32(state2[(i*4) + nResult]);
 548
 549                     CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 550                     CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 551
 552                     if (bnTargetProofOfStake >= CBigNum(nHashProofOfStake))
 553                         solutions.push_back(std::pair<uint256,uint32_t>(nHashProofOfStake, nTime));
 554                 }
 555             }
 556         }
 557     }
 558
 559     void Do_generic()
 560     {
 561         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 562
 563         // Init new sha256 context and update it
 564         //   with first 24 bytes of kernel
 565         SHA256_CTX workerCtx;
 566         SHA256_Init(&workerCtx);
 567         SHA256_Update(&workerCtx, kernel, 8 + 16);
 568         SHA256_CTX ctx = workerCtx;
 569
 570         // Sha256 result buffer
 571         uint32_t hashProofOfStake[8];
 572
 573         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 574         CBigNum bnTargetPerCoinDay;
 575         bnTargetPerCoinDay.SetCompact(nBits);
 576
 577         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 578             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 579
 580         // Search forward in time from the given timestamp
 581         // Stopping search in case of shutting down
 582         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 583         {
 584             // Complete first hashing iteration
 585             uint256 hash1;
 586             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 587             SHA256_Final((unsigned char*)&hash1, &ctx);
 588
 589             // Restore context
 590             ctx = workerCtx;
 591
 592             // Finally, calculate kernel hash
 593             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 594
 595             // Skip if hash doesn't satisfy the maximum target
 596             if (hashProofOfStake[7] > nMaxTarget32)
 597                 continue;
 598
 599             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 600             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 601
 602             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 603                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 604         }
 605     }
 606
 607     void Do()
 608     {
 609         if (fUse4Way)
 610             Do_4way();
 611         else
 612             Do_generic();
 613     }
 614
 615     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 616     {
 617         return solutions;
 618     }
 619
 620 private:
 621     std::vector<std::pair<uint256,uint32_t> > solutions;
 622
 623     uint8_t *kernel;
 624     uint32_t nBits;
 625     uint32_t nInputTxTime;
 626     CBigNum  bnValueIn;
 627     uint32_t nIntervalBegin;
 628     uint32_t nIntervalEnd;
 629 };
 630
 631 #else
 632 class ScanMidstateWorker
 633 {
 634 public:
 635     ScanMidstateWorker()
 636     { }
 637     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 638         : nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 639     {
 640         // Init new sha256 context and update it
 641         //   with first 24 bytes of kernel
 642         SHA256_Init(&workerCtx);
 643         SHA256_Update(&workerCtx, kernel, 8 + 16);
 644         solutions = vector<std::pair<uint256,uint32_t> >();
 645     }
 646
 647     void Do()
 648     {
 649         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 650         SHA256_CTX ctx = workerCtx;
 651
 652         // Sha256 result buffer
 653         uint32_t hashProofOfStake[8];
 654
 655         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 656         CBigNum bnTargetPerCoinDay;
 657         bnTargetPerCoinDay.SetCompact(nBits);
 658
 659         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 660             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 661
 662         // Search forward in time from the given timestamp
 663         // Stopping search in case of shutting down
 664         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 665         {
 666             // Complete first hashing iteration
 667             uint256 hash1;
 668             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 669             SHA256_Final((unsigned char*)&hash1, &ctx);
 670
 671             // Restore context
 672             ctx = workerCtx;
 673
 674             // Finally, calculate kernel hash
 675             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 676
 677             // Skip if hash doesn't satisfy the maximum target
 678             if (hashProofOfStake[7] > nMaxTarget32)
 679                 continue;
 680
 681             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 682             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 683
 684             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 685                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 686         }
 687     }
 688
 689     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 690     {
 691         return solutions;
 692     }
 693
 694 private:
 695     SHA256_CTX workerCtx;
 696     std::vector<std::pair<uint256,uint32_t> > solutions;
 697
 698     uint32_t nBits;
 699     uint32_t nInputTxTime;
 700     CBigNum  bnValueIn;
 701     uint32_t nIntervalBegin;
 702     uint32_t nIntervalEnd;
 703 };
 704
 705 #endif
 706 // Scan given kernel for solution
 707 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)
 708 {
 709     // TODO: custom threads amount
 710
 711     uint32_t nThreads = boost::thread::hardware_concurrency();
 712     uint32_t nPart = (SearchInterval.second - SearchInterval.first) / nThreads;
 713
 714
 715     ScanMidstateWorker *workers = new ScanMidstateWorker[nThreads];
 716
 717     boost::thread_group group;
 718     for(size_t i = 0; i < nThreads; i++)
 719     {
 720         uint32_t nBegin = SearchInterval.first + nPart * i;
 721         uint32_t nEnd = SearchInterval.first + nPart * (i + 1);
 722         workers[i] = ScanMidstateWorker(kernel, nBits, nInputTxTime, nValueIn, nBegin, nEnd);
 723         boost::function<void()> workerFnc = boost::bind(&ScanMidstateWorker::Do, &workers[i]);
 724         group.create_thread(workerFnc);
 725     }
 726
 727     group.join_all();
 728     solutions.clear();
 729
 730     for(size_t i = 0; i < nThreads; i++)
 731     {
 732         std::vector<std::pair<uint256, uint32_t> > ws = workers[i].GetSolutions();
 733         solutions.insert(solutions.end(), ws.begin(), ws.end());
 734     }
 735
 736     delete [] workers;
 737
 738     if (solutions.size() == 0)
 739     {
 740         // no solutions
 741         return false;
 742     }
 743
 744     return true;
 745 }
 746
 747 // Scan given midstate for solution
 748 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)
 749 {
 750     CBigNum bnTargetPerCoinDay;
 751     bnTargetPerCoinDay.SetCompact(nBits);
 752
 753     // Get maximum possible target to filter out the majority of obviously insufficient hashes
 754     CBigNum bnMaxTargetPerCoinDay = bnTargetPerCoinDay * CBigNum(nValueIn) * nStakeMaxAge / COIN / nOneDay;
 755     uint256 maxTarget = bnMaxTargetPerCoinDay.getuint256();
 756
 757     SHA256_CTX ctxCopy = ctx;
 758
 759     // Search backward in time from the given timestamp
 760     // Stopping search in case of shutting down
 761     for (uint32_t nTimeTx=SearchInterval.first; nTimeTx>SearchInterval.second && !fShutdown; nTimeTx--)
 762     {
 763         // Complete first hashing iteration
 764         uint256 hash1;
 765         SHA256_Update(&ctxCopy, (unsigned char*)&nTimeTx, 4);
 766         SHA256_Final((unsigned char*)&hash1, &ctxCopy);
 767
 768         // Restore context
 769         ctxCopy = ctx;
 770
 771         // Finally, calculate kernel hash
 772         uint256 hashProofOfStake;
 773         SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 774
 775         // Skip if hash doesn't satisfy the maximum target
 776         if (hashProofOfStake > maxTarget)
 777             continue;
 778
 779         CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 780         CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 781
 782         if (bnTargetProofOfStake >= CBigNum(hashProofOfStake))
 783         {
 784             solution.first = hashProofOfStake;
 785             solution.second = nTimeTx;
 786
 787             return true;
 788         }
 789     }
 790
 791     return false;
 792 }
 793
 794 // Check kernel hash target and coinstake signature
 795 bool CheckProofOfStake(const CTransaction& tx, unsigned int nBits, uint256& hashProofOfStake, uint256& targetProofOfStake)
 796 {
 797     if (!tx.IsCoinStake())
 798         return error("CheckProofOfStake() : called on non-coinstake %s", tx.GetHash().ToString().c_str());
 799
 800     // Kernel (input 0) must match the stake hash target per coin age (nBits)
 801     const CTxIn& txin = tx.vin[0];
 802
 803     // First try finding the previous transaction in database
 804     CTxDB txdb("r");
 805     CTransaction txPrev;
 806     CTxIndex txindex;
 807     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
 808         return tx.DoS(1, error("CheckProofOfStake() : INFO: read txPrev failed"));  // previous transaction not in main chain, may occur during initial download
 809
 810 #ifndef USE_LEVELDB
 811     txdb.Close();
 812 #endif
 813
 814     // Verify signature
 815     if (!VerifySignature(txPrev, tx, 0, MANDATORY_SCRIPT_VERIFY_FLAGS, 0))
 816         return tx.DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", tx.GetHash().ToString().c_str()));
 817
 818     // Read block header
 819     CBlock block;
 820     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
 821         return fDebug? error("CheckProofOfStake() : read block failed") : false; // unable to read block of previous transaction
 822
 823     if (!CheckStakeKernelHash(nBits, block, txindex.pos.nTxPos - txindex.pos.nBlockPos, txPrev, txin.prevout, tx.nTime, hashProofOfStake, targetProofOfStake, fDebug))
 824         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
 825
 826     return true;
 827 }
 828
 829 // Get stake modifier checksum
 830 uint32_t GetStakeModifierChecksum(const CBlockIndex* pindex)
 831 {
 832     assert (pindex->pprev || pindex->GetBlockHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
 833     // Hash previous checksum with flags, hashProofOfStake and nStakeModifier
 834     CDataStream ss(SER_GETHASH, 0);
 835     if (pindex->pprev)
 836         ss << pindex->pprev->nStakeModifierChecksum;
 837     ss << pindex->nFlags << pindex->hashProofOfStake << pindex->nStakeModifier;
 838     uint256 hashChecksum = Hash(ss.begin(), ss.end());
 839     hashChecksum >>= (256 - 32);
 840     return static_cast<uint32_t>(hashChecksum.Get64());
 841 }
 842
 843 // Check stake modifier hard checkpoints
 844 bool CheckStakeModifierCheckpoints(int nHeight, uint32_t nStakeModifierChecksum)
 845 {
 846     MapModifierCheckpoints& checkpoints = (fTestNet ? mapStakeModifierCheckpointsTestNet : mapStakeModifierCheckpoints);
 847
 848     if (checkpoints.count(nHeight))
 849         return nStakeModifierChecksum == checkpoints[nHeight];
 850     return true;
 851 }