src/kernel.cpp

   1 // Copyright (c) 2012-2013 The PPCoin developers
   2 // Distributed under the MIT/X11 software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include <boost/assign/list_of.hpp>
   6
   7 #include "kernel.h"
   8 #include "txdb.h"
   9
  10 extern unsigned int nStakeMaxAge;
  11 extern unsigned int nStakeTargetSpacing;
  12
  13 using namespace std;
  14
  15
  16 // Protocol switch time for fixed kernel modifier interval
  17 unsigned int nModifierSwitchTime  = 1413763200;    // Mon, 20 Oct 2014 00:00:00 GMT
  18 unsigned int nModifierTestSwitchTime = 1397520000; // Tue, 15 Apr 2014 00:00:00 GMT
  19
  20 // Note: user must upgrade before the protocol switch deadline, otherwise it's required to
  21 //   re-download the blockchain. The timestamp of upgrade is recorded in the blockchain
  22 //   database.
  23 unsigned int nModifierUpgradeTime = 0;
  24
  25 typedef std::map<int, unsigned int> MapModifierCheckpoints;
  26
  27 // Hard checkpoints of stake modifiers to ensure they are deterministic
  28 static std::map<int, unsigned int> mapStakeModifierCheckpoints =
  29     boost::assign::map_list_of
  30         ( 0, 0x0e00670bu )
  31         ( 12661, 0x5d84115du )
  32         (143990, 0x9c592c78u )
  33         (149000, 0x48f2bdc4u )
  34         (160000, 0x789df0f0u )
  35         (200000, 0x01ec1503u )
  36     ;
  37
  38 // Hard checkpoints of stake modifiers to ensure they are deterministic (testNet)
  39 static std::map<int, unsigned int> mapStakeModifierCheckpointsTestNet =
  40     boost::assign::map_list_of
  41         ( 0, 0x0e00670bu )
  42     ;
  43
  44 // Pregenerated entropy bits table (from genesis to #9689)
  45 //
  46 // Bits are packed into array of 256 bit integers:
  47 //
  48 // * array index calculated as nHeight / 256
  49 // * position of bit is calculated as nHeight & 0xFF.
  50 //
  51 const uint256 entropyStore[] = {
  52     uint256("0x4555b4dcc1d690ddd9b810c90c66e82b18bf4f43cc887246c418383ec120a5ab"),
  53     uint256("0xaa6d1198412fa77608addf6549c9198a22155e8afd7a9ded6179f6b7cfc66b0c"),
  54     uint256("0x9442fabfa4116fb14a9769c2eea003845a1f5c3a0260f36b497d68f3a3cd4078"),
  55     uint256("0x0e769042a9a98e42388195d699574b822d06515f7053ad884c53d7ee059f05b1"),
  56     uint256("0x7005aac20baf70251aebfe3f1b95987d83ef1e3e6963de8fed601d4dd07bf7cf"),
  57     uint256("0x58952c5c3de188f2e33c38d3f53d7bf44f9bc545a4289d266696273fa821be66"),
  58     uint256("0x50b6c2ed780c08aaec3f7665b1b6004206243e3866456fc910b83b52d07eeb63"),
  59     uint256("0x563841eefca85ba3384986c58100408ae3f1ba2ac727e1ac910ce154a06c702f"),
  60     uint256("0x79275b03938b3e27a9b01a7f7953c6c487c58355f5d4169accfbb800213ffd13"),
  61     uint256("0xd783f2538b3ed18f135af90adc687c5646d93aeaeaabc6667be94f7aa0a2d366"),
  62     uint256("0xb441d0c175c40c8e88b09d88ea008af79cbed2d28219427d2e72fda682974db8"),
  63     uint256("0x3204c43bd41f2e19628af3b0c9aca3db15bca4c8705d51056e7b17a319c04715"),
  64     uint256("0x7e80e6ab7857d8f2f261a0a49c783bd800b365b8c9b85cc0e13f73904b0dcaa9"),
  65     uint256("0xefaaee60ed82d2ad145c0e347941fdb131eb8fd289a45eef07121a93f283c5f1"),
  66     uint256("0x3efc86e4334da332c1fd4c12513c40cff689f3efdc7f9913230822adacdda4f9"),
  67     uint256("0xf0d6b8f38599a017fa35d1fbbf9ef51eca5ebc5b286aadba40c4c3e1d9bace0c"),
  68     uint256("0x286a67f27323486036a0a92d35382fc8963c0c00bad331723318b4b9fdb2b56e"),
  69     uint256("0xecbfaaa6567c54f08c4d5bd0118a2d7b58740f42cbfc73aa1536c1f5f76de87c"),
  70     uint256("0xf9a4de1c5c46520de5aaf10d3796cf0e27ddce98b3398357f5726a949664e308"),
  71     uint256("0xd75e6c4dc4be08401e3478d2467d9ab96a62af4f255c04a82c41af0de0a487bb"),
  72     uint256("0x1a82c3bc6ad6047294c16571b5e2b7316c97bf8813e7da15798b9820d67e39f2"),
  73     uint256("0xb49be0080de564e01829ded7e7971979565a741c5975dc9978dcc020192d396c"),
  74     uint256("0x0d8eed113be67663b5a15a0625a9b49792b5ea59c005c4f405914877acab7000"),
  75     uint256("0x8f9d46e2bc05a218ffa942965b747056197d393b097085523640cd59e07fe7c7"),
  76     uint256("0x7a63ab40bc7f40ac2ebe9ede438d97b45fa6ed6f8419016da8d5f7a670111dda"),
  77     uint256("0x63fbcc080448c43d6cf915c958314feff7a95a52ba43a68c05fc281d3a522d25"),
  78     uint256("0xf834cf824c326d3ea861ea1e85dc3289265e37045981e28208e7344a7f8081d7"),
  79     uint256("0xb4edc22ec98cc49b2f5af5bae3f52f5e6058280f74f2c432c2dd89ae49acceb8"),
  80     uint256("0x0fe596037dcf81bf5c64f39755261c404ed088af5c8c31dd7549b6657ee92365"),
  81     uint256("0xbbad51a0aeba254b01d18c328de9e932b9b859b61e622c325d64e2211b5e413d"),
  82     uint256("0xabf0194cc787be938bc51c7fdf1cae4ec79e65ebab8fa8b8f40541c44ef384b0"),
  83     uint256("0x83bc12d6fdbd3e854cb91c4ca7dfba3c38e8714121af88c8a8abdb33e5002438"),
  84     uint256("0x71a2513026cabaedcbe55aeb6dc8049e5b763a3f54f10c33dd333624f764b38c"),
  85     uint256("0xee6725632ff5c025dff6a18cd059875dcae20f399b03bccba13d9d5fcf6d9d9a"),
  86     uint256("0xa168a2741d1e7e50cc74b79f695c25ffd3576e6bd61353c2a20e569fd63b2dac"),
  87     uint256("0x6e462d2a87bfde9398b6747f94a8ed6a01e4d96c5b4372df5c910c106c48bd13"),
  88     uint256("0x8eeb696181957c4b22434028990f49cb30006827c73860e77e2eecf5c38be99d"),
  89     uint256("0x3188aaa65877b166f05cdc48f55b1f77a7d6fb221c395596d990ae5647e9ba96")
  90 };
  91
  92 // Whether the given block is subject to new modifier protocol
  93 bool IsFixedModifierInterval(unsigned int nTimeBlock)
  94 {
  95     return (nTimeBlock >= (fTestNet? nModifierTestSwitchTime : nModifierSwitchTime));
  96 }
  97
  98 // Get the last stake modifier and its generation time from a given block
  99 static bool GetLastStakeModifier(const CBlockIndex* pindex, uint64_t& nStakeModifier, int64_t& nModifierTime)
 100 {
 101     if (!pindex)
 102         return error("GetLastStakeModifier: null pindex");
 103     while (pindex && pindex->pprev && !pindex->GeneratedStakeModifier())
 104         pindex = pindex->pprev;
 105     if (!pindex->GeneratedStakeModifier())
 106         return error("GetLastStakeModifier: no generation at genesis block");
 107     nStakeModifier = pindex->nStakeModifier;
 108     nModifierTime = pindex->GetBlockTime();
 109     return true;
 110 }
 111
 112 // Get selection interval section (in seconds)
 113 static int64_t GetStakeModifierSelectionIntervalSection(int nSection)
 114 {
 115     assert (nSection >= 0 && nSection < 64);
 116     return (nModifierInterval * 63 / (63 + ((63 - nSection) * (MODIFIER_INTERVAL_RATIO - 1))));
 117 }
 118
 119 // Get stake modifier selection interval (in seconds)
 120 static int64_t GetStakeModifierSelectionInterval()
 121 {
 122     int64_t nSelectionInterval = 0;
 123     for (int nSection=0; nSection<64; nSection++)
 124         nSelectionInterval += GetStakeModifierSelectionIntervalSection(nSection);
 125     return nSelectionInterval;
 126 }
 127
 128 // select a block from the candidate blocks in vSortedByTimestamp, excluding
 129 // already selected blocks in vSelectedBlocks, and with timestamp up to
 130 // nSelectionIntervalStop.
 131 static bool SelectBlockFromCandidates(vector<pair<int64_t, uint256> >& vSortedByTimestamp, map<uint256, const CBlockIndex*>& mapSelectedBlocks,
 132     int64_t nSelectionIntervalStop, uint64_t nStakeModifierPrev, const CBlockIndex** pindexSelected)
 133 {
 134     bool fSelected = false;
 135     uint256 hashBest = 0;
 136     *pindexSelected = (const CBlockIndex*) 0;
 137     BOOST_FOREACH(const PAIRTYPE(int64_t, uint256)& item, vSortedByTimestamp)
 138     {
 139         if (!mapBlockIndex.count(item.second))
 140             return error("SelectBlockFromCandidates: failed to find block index for candidate block %s", item.second.ToString().c_str());
 141         const CBlockIndex* pindex = mapBlockIndex[item.second];
 142         if (fSelected && pindex->GetBlockTime() > nSelectionIntervalStop)
 143             break;
 144         if (mapSelectedBlocks.count(pindex->GetBlockHash()) > 0)
 145             continue;
 146         // compute the selection hash by hashing its proof-hash and the
 147         // previous proof-of-stake modifier
 148         uint256 hashProof = pindex->IsProofOfStake()? pindex->hashProofOfStake : pindex->GetBlockHash();
 149         CDataStream ss(SER_GETHASH, 0);
 150         ss << hashProof << nStakeModifierPrev;
 151         uint256 hashSelection = Hash(ss.begin(), ss.end());
 152         // the selection hash is divided by 2**32 so that proof-of-stake block
 153         // is always favored over proof-of-work block. this is to preserve
 154         // the energy efficiency property
 155         if (pindex->IsProofOfStake())
 156             hashSelection >>= 32;
 157         if (fSelected && hashSelection < hashBest)
 158         {
 159             hashBest = hashSelection;
 160             *pindexSelected = (const CBlockIndex*) pindex;
 161         }
 162         else if (!fSelected)
 163         {
 164             fSelected = true;
 165             hashBest = hashSelection;
 166             *pindexSelected = (const CBlockIndex*) pindex;
 167         }
 168     }
 169     if (fDebug && GetBoolArg("-printstakemodifier"))
 170         printf("SelectBlockFromCandidates: selection hash=%s\n", hashBest.ToString().c_str());
 171     return fSelected;
 172 }
 173
 174 // Stake Modifier (hash modifier of proof-of-stake):
 175 // The purpose of stake modifier is to prevent a txout (coin) owner from
 176 // computing future proof-of-stake generated by this txout at the time
 177 // of transaction confirmation. To meet kernel protocol, the txout
 178 // must hash with a future stake modifier to generate the proof.
 179 // Stake modifier consists of bits each of which is contributed from a
 180 // selected block of a given block group in the past.
 181 // The selection of a block is based on a hash of the block's proof-hash and
 182 // the previous stake modifier.
 183 // Stake modifier is recomputed at a fixed time interval instead of every
 184 // block. This is to make it difficult for an attacker to gain control of
 185 // additional bits in the stake modifier, even after generating a chain of
 186 // blocks.
 187 bool ComputeNextStakeModifier(const CBlockIndex* pindexCurrent, uint64_t& nStakeModifier, bool& fGeneratedStakeModifier)
 188 {
 189     nStakeModifier = 0;
 190     fGeneratedStakeModifier = false;
 191     const CBlockIndex* pindexPrev = pindexCurrent->pprev;
 192     if (!pindexPrev)
 193     {
 194         fGeneratedStakeModifier = true;
 195         return true;  // genesis block's modifier is 0
 196     }
 197
 198     // First find current stake modifier and its generation block time
 199     // if it's not old enough, return the same stake modifier
 200     int64_t nModifierTime = 0;
 201     if (!GetLastStakeModifier(pindexPrev, nStakeModifier, nModifierTime))
 202         return error("ComputeNextStakeModifier: unable to get last modifier");
 203     if (fDebug)
 204     {
 205         printf("ComputeNextStakeModifier: prev modifier=0x%016" PRIx64 " time=%s epoch=%u\n", nStakeModifier, DateTimeStrFormat(nModifierTime).c_str(), (unsigned int)nModifierTime);
 206     }
 207     if (nModifierTime / nModifierInterval >= pindexPrev->GetBlockTime() / nModifierInterval)
 208     {
 209         if (fDebug)
 210         {
 211             printf("ComputeNextStakeModifier: no new interval keep current modifier: pindexPrev nHeight=%d nTime=%u\n", pindexPrev->nHeight, (unsigned int)pindexPrev->GetBlockTime());
 212         }
 213         return true;
 214     }
 215     if (nModifierTime / nModifierInterval >= pindexCurrent->GetBlockTime() / nModifierInterval)
 216     {
 217         // fixed interval protocol requires current block timestamp also be in a different modifier interval
 218         if (IsFixedModifierInterval(pindexCurrent->nTime))
 219         {
 220             if (fDebug)
 221             {
 222                 printf("ComputeNextStakeModifier: no new interval keep current modifier: pindexCurrent nHeight=%d nTime=%u\n", pindexCurrent->nHeight, (unsigned int)pindexCurrent->GetBlockTime());
 223             }
 224             return true;
 225         }
 226         else
 227         {
 228             if (fDebug)
 229             {
 230                 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());
 231             }
 232         }
 233     }
 234
 235     // Sort candidate blocks by timestamp
 236     vector<pair<int64_t, uint256> > vSortedByTimestamp;
 237     vSortedByTimestamp.reserve(64 * nModifierInterval / nStakeTargetSpacing);
 238     int64_t nSelectionInterval = GetStakeModifierSelectionInterval();
 239     int64_t nSelectionIntervalStart = (pindexPrev->GetBlockTime() / nModifierInterval) * nModifierInterval - nSelectionInterval;
 240     const CBlockIndex* pindex = pindexPrev;
 241     while (pindex && pindex->GetBlockTime() >= nSelectionIntervalStart)
 242     {
 243         vSortedByTimestamp.push_back(make_pair(pindex->GetBlockTime(), pindex->GetBlockHash()));
 244         pindex = pindex->pprev;
 245     }
 246     int nHeightFirstCandidate = pindex ? (pindex->nHeight + 1) : 0;
 247     reverse(vSortedByTimestamp.begin(), vSortedByTimestamp.end());
 248     sort(vSortedByTimestamp.begin(), vSortedByTimestamp.end());
 249
 250     // Select 64 blocks from candidate blocks to generate stake modifier
 251     uint64_t nStakeModifierNew = 0;
 252     int64_t nSelectionIntervalStop = nSelectionIntervalStart;
 253     map<uint256, const CBlockIndex*> mapSelectedBlocks;
 254     for (int nRound=0; nRound<min(64, (int)vSortedByTimestamp.size()); nRound++)
 255     {
 256         // add an interval section to the current selection round
 257         nSelectionIntervalStop += GetStakeModifierSelectionIntervalSection(nRound);
 258         // select a block from the candidates of current round
 259         if (!SelectBlockFromCandidates(vSortedByTimestamp, mapSelectedBlocks, nSelectionIntervalStop, nStakeModifier, &pindex))
 260             return error("ComputeNextStakeModifier: unable to select block at round %d", nRound);
 261         // write the entropy bit of the selected block
 262         nStakeModifierNew |= (((uint64_t)pindex->GetStakeEntropyBit()) << nRound);
 263         // add the selected block from candidates to selected list
 264         mapSelectedBlocks.insert(make_pair(pindex->GetBlockHash(), pindex));
 265         if (fDebug && GetBoolArg("-printstakemodifier"))
 266             printf("ComputeNextStakeModifier: selected round %d stop=%s height=%d bit=%d\n", nRound, DateTimeStrFormat(nSelectionIntervalStop).c_str(), pindex->nHeight, pindex->GetStakeEntropyBit());
 267     }
 268
 269     // Print selection map for visualization of the selected blocks
 270     if (fDebug && GetBoolArg("-printstakemodifier"))
 271     {
 272         string strSelectionMap = "";
 273         // '-' indicates proof-of-work blocks not selected
 274         strSelectionMap.insert(0, pindexPrev->nHeight - nHeightFirstCandidate + 1, '-');
 275         pindex = pindexPrev;
 276         while (pindex && pindex->nHeight >= nHeightFirstCandidate)
 277         {
 278             // '=' indicates proof-of-stake blocks not selected
 279             if (pindex->IsProofOfStake())
 280                 strSelectionMap.replace(pindex->nHeight - nHeightFirstCandidate, 1, "=");
 281             pindex = pindex->pprev;
 282         }
 283         BOOST_FOREACH(const PAIRTYPE(uint256, const CBlockIndex*)& item, mapSelectedBlocks)
 284         {
 285             // 'S' indicates selected proof-of-stake blocks
 286             // 'W' indicates selected proof-of-work blocks
 287             strSelectionMap.replace(item.second->nHeight - nHeightFirstCandidate, 1, item.second->IsProofOfStake()? "S" : "W");
 288         }
 289         printf("ComputeNextStakeModifier: selection height [%d, %d] map %s\n", nHeightFirstCandidate, pindexPrev->nHeight, strSelectionMap.c_str());
 290     }
 291     if (fDebug)
 292     {
 293         printf("ComputeNextStakeModifier: new modifier=0x%016" PRIx64 " time=%s\n", nStakeModifierNew, DateTimeStrFormat(pindexPrev->GetBlockTime()).c_str());
 294     }
 295
 296     nStakeModifier = nStakeModifierNew;
 297     fGeneratedStakeModifier = true;
 298     return true;
 299 }
 300
 301 // The stake modifier used to hash for a stake kernel is chosen as the stake
 302 // modifier about a selection interval later than the coin generating the kernel
 303 static bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64_t& nStakeModifier, int& nStakeModifierHeight, int64_t& nStakeModifierTime, bool fPrintProofOfStake)
 304 {
 305     nStakeModifier = 0;
 306     if (!mapBlockIndex.count(hashBlockFrom))
 307         return error("GetKernelStakeModifier() : block not indexed");
 308     const CBlockIndex* pindexFrom = mapBlockIndex[hashBlockFrom];
 309     nStakeModifierHeight = pindexFrom->nHeight;
 310     nStakeModifierTime = pindexFrom->GetBlockTime();
 311     int64_t nStakeModifierSelectionInterval = GetStakeModifierSelectionInterval();
 312     const CBlockIndex* pindex = pindexFrom;
 313     // loop to find the stake modifier later by a selection interval
 314     while (nStakeModifierTime < pindexFrom->GetBlockTime() + nStakeModifierSelectionInterval)
 315     {
 316         if (!pindex->pnext)
 317         {   // reached best block; may happen if node is behind on block chain
 318             if (fPrintProofOfStake || (pindex->GetBlockTime() + nStakeMinAge - nStakeModifierSelectionInterval > GetAdjustedTime()))
 319                 return error("GetKernelStakeModifier() : reached best block %s at height %d from block %s",
 320                     pindex->GetBlockHash().ToString().c_str(), pindex->nHeight, hashBlockFrom.ToString().c_str());
 321             else
 322                 return false;
 323         }
 324         pindex = pindex->pnext;
 325         if (pindex->GeneratedStakeModifier())
 326         {
 327             nStakeModifierHeight = pindex->nHeight;
 328             nStakeModifierTime = pindex->GetBlockTime();
 329         }
 330     }
 331     nStakeModifier = pindex->nStakeModifier;
 332     return true;
 333 }
 334
 335 bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64_t& nStakeModifier)
 336 {
 337     int nStakeModifierHeight;
 338     int64_t nStakeModifierTime;
 339
 340     return GetKernelStakeModifier(hashBlockFrom, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, false);
 341 }
 342
 343
 344 // ppcoin kernel protocol
 345 // coinstake must meet hash target according to the protocol:
 346 // kernel (input 0) must meet the formula
 347 //     hash(nStakeModifier + txPrev.block.nTime + txPrev.offset + txPrev.nTime + txPrev.vout.n + nTime) < bnTarget * nCoinDayWeight
 348 // this ensures that the chance of getting a coinstake is proportional to the
 349 // amount of coin age one owns.
 350 // The reason this hash is chosen is the following:
 351 //   nStakeModifier: scrambles computation to make it very difficult to precompute
 352 //                  future proof-of-stake at the time of the coin's confirmation
 353 //   txPrev.block.nTime: prevent nodes from guessing a good timestamp to
 354 //                       generate transaction for future advantage
 355 //   txPrev.offset: offset of txPrev inside block, to reduce the chance of
 356 //                  nodes generating coinstake at the same time
 357 //   txPrev.nTime: reduce the chance of nodes generating coinstake at the same
 358 //                 time
 359 //   txPrev.vout.n: output number of txPrev, to reduce the chance of nodes
 360 //                  generating coinstake at the same time
 361 //   block/tx hash should not be used here as they can be generated in vast
 362 //   quantities so as to generate blocks faster, degrading the system back into
 363 //   a proof-of-work situation.
 364 //
 365 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)
 366 {
 367     if (nTimeTx < txPrev.nTime)  // Transaction timestamp violation
 368         return error("CheckStakeKernelHash() : nTime violation");
 369
 370     uint32_t nTimeBlockFrom = blockFrom.GetBlockTime();
 371     if (nTimeBlockFrom + nStakeMinAge > nTimeTx) // Min age requirement
 372         return error("CheckStakeKernelHash() : min age violation");
 373
 374     CBigNum bnTargetPerCoinDay;
 375     bnTargetPerCoinDay.SetCompact(nBits);
 376     int64_t nValueIn = txPrev.vout[prevout.n].nValue;
 377
 378     uint256 hashBlockFrom = blockFrom.GetHash();
 379
 380     CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)txPrev.nTime, (int64_t)nTimeTx) / COIN / nOneDay;
 381     targetProofOfStake = (bnCoinDayWeight * bnTargetPerCoinDay).getuint256();
 382
 383     // Calculate hash
 384     CDataStream ss(SER_GETHASH, 0);
 385     uint64_t nStakeModifier = 0;
 386     int nStakeModifierHeight = 0;
 387     int64_t nStakeModifierTime = 0;
 388
 389     if (!GetKernelStakeModifier(hashBlockFrom, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake))
 390         return false;
 391     ss << nStakeModifier;
 392
 393     ss << nTimeBlockFrom << nTxPrevOffset << txPrev.nTime << prevout.n << nTimeTx;
 394     hashProofOfStake = Hash(ss.begin(), ss.end());
 395     if (fPrintProofOfStake)
 396     {
 397         printf("CheckStakeKernelHash() : using modifier 0x%016" PRIx64 " at height=%d timestamp=%s for block from height=%d timestamp=%s\n",
 398             nStakeModifier, nStakeModifierHeight,
 399             DateTimeStrFormat(nStakeModifierTime).c_str(),
 400             mapBlockIndex[hashBlockFrom]->nHeight,
 401             DateTimeStrFormat(blockFrom.GetBlockTime()).c_str());
 402         printf("CheckStakeKernelHash() : check modifier=0x%016" PRIx64 " nTimeBlockFrom=%u nTxPrevOffset=%u nTimeTxPrev=%u nPrevout=%u nTimeTx=%u hashTarget=%s hashProof=%s\n",
 403             nStakeModifier,
 404             nTimeBlockFrom, nTxPrevOffset, txPrev.nTime, prevout.n, nTimeTx,
 405             targetProofOfStake.ToString().c_str(), hashProofOfStake.ToString().c_str());
 406     }
 407
 408     // Now check if proof-of-stake hash meets target protocol
 409     if (CBigNum(hashProofOfStake) > bnCoinDayWeight * bnTargetPerCoinDay)
 410         return false;
 411     if (fDebug && !fPrintProofOfStake)
 412     {
 413         printf("CheckStakeKernelHash() : using modifier 0x%016" PRIx64 " at height=%d timestamp=%s for block from height=%d timestamp=%s\n",
 414             nStakeModifier, nStakeModifierHeight,
 415             DateTimeStrFormat(nStakeModifierTime).c_str(),
 416             mapBlockIndex[hashBlockFrom]->nHeight,
 417             DateTimeStrFormat(blockFrom.GetBlockTime()).c_str());
 418         printf("CheckStakeKernelHash() : pass modifier=0x%016" PRIx64 " nTimeBlockFrom=%u nTxPrevOffset=%u nTimeTxPrev=%u nPrevout=%u nTimeTx=%u hashTarget=%s hashProof=%s\n",
 419             nStakeModifier,
 420             nTimeBlockFrom, nTxPrevOffset, txPrev.nTime, prevout.n, nTimeTx,
 421             targetProofOfStake.ToString().c_str(), hashProofOfStake.ToString().c_str());
 422     }
 423     return true;
 424 }
 425
 426
 427 #ifdef USE_YASM
 428
 429 // SHA256 initial state
 430 static const uint32_t init[8] = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };
 431
 432 // 8000000000000000000000000000000000000000000000000000000000000000000000e0
 433 static const uint32_t block1_suffix[9] = { 0x00000080, 0, 0, 0, 0, 0, 0, 0, 0xe0000000 };
 434
 435 // 8000000000000000000000000000000000000000000000000000000000000100
 436 static const uint32_t block2_suffix[8] = { 0x00000080, 0, 0, 0, 0, 0, 0, 0x00010000 };
 437
 438 // TODO: cpuid detection of supported instruction sets
 439
 440 extern "C" void sha256_avx(void *input_data, uint32_t digest[8], uint64_t num_blks);
 441 extern "C" void sha256_avx_swap(void *input_data, uint32_t digest[8], uint64_t num_blks);
 442
 443 // Not used yet
 444 extern "C" void sha256_sse4(void *input_data, uint32_t digest[8], uint64_t num_blks);
 445 extern "C" void sha256_sse4_swap(void *input_data, uint32_t digest[8], uint64_t num_blks);
 446
 447 class ScanMidstateWorker
 448 {
 449 public:
 450     ScanMidstateWorker()
 451     { }
 452     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 453         : kernel(kernel), nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 454     {
 455         solutions = vector<std::pair<uint256,uint32_t> >();
 456     }
 457
 458     void Do()
 459     {
 460         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 461
 462         // Sha256 result buffer
 463         uint32_t hashProofOfStake[8];
 464
 465         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 466         CBigNum bnTargetPerCoinDay;
 467         bnTargetPerCoinDay.SetCompact(nBits);
 468
 469         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 470             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 471
 472         uint8_t data_block[64];
 473         uint8_t data_block2[64];
 474
 475         // Copy static part of kernel
 476         memcpy(&data_block[0], kernel, 24);
 477
 478         memcpy(&data_block[28], &block1_suffix[0], 9 * sizeof(uint32_t));
 479         memcpy(&data_block2[32], &block2_suffix[0], 8 * sizeof(uint32_t));
 480
 481         // Search forward in time from the given timestamp
 482         // Stopping search in case of shutting down
 483         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 484         {
 485             memcpy(&data_block[24], &nTimeTx, 4); // Timestamp
 486
 487             memcpy(&data_block2[0], &init[0], 8 * sizeof(uint32_t));
 488             sha256_avx_swap(&data_block[0], (uint32_t *) &data_block2[0], 1);
 489             memcpy(&hashProofOfStake[0], &init[0], 8 * sizeof(uint32_t));
 490             sha256_avx(&data_block2[0], &hashProofOfStake[0], 1);
 491
 492             // Skip if hash doesn't satisfy the maximum target
 493             if (__builtin_bswap32(hashProofOfStake[7]) > nMaxTarget32)
 494                 continue;
 495
 496             // Swap byte order
 497             for(int i = 0; i < 8; i++)
 498                 hashProofOfStake[i] = __builtin_bswap32(hashProofOfStake[i]);
 499
 500             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 501             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 502
 503             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 504                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 505         }
 506     }
 507
 508     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 509     {
 510         return solutions;
 511     }
 512
 513 private:
 514     std::vector<std::pair<uint256,uint32_t> > solutions;
 515
 516     uint8_t *kernel;
 517     uint32_t nBits;
 518     uint32_t nInputTxTime;
 519     CBigNum  bnValueIn;
 520     uint32_t nIntervalBegin;
 521     uint32_t nIntervalEnd;
 522 };
 523
 524 #else
 525 class ScanMidstateWorker
 526 {
 527 public:
 528     ScanMidstateWorker()
 529     { }
 530     ScanMidstateWorker(unsigned char *kernel, uint32_t nBits, uint32_t nInputTxTime, int64_t nValueIn, uint32_t nIntervalBegin, uint32_t nIntervalEnd)
 531         : nBits(nBits), nInputTxTime(nInputTxTime), bnValueIn(nValueIn), nIntervalBegin(nIntervalBegin), nIntervalEnd(nIntervalEnd)
 532     {
 533         // Init new sha256 context and update it
 534         //   with first 24 bytes of kernel
 535         SHA256_Init(&workerCtx);
 536         SHA256_Update(&workerCtx, kernel, 8 + 16);
 537         solutions = vector<std::pair<uint256,uint32_t> >();
 538     }
 539
 540     void Do()
 541     {
 542         SetThreadPriority(THREAD_PRIORITY_LOWEST);
 543         SHA256_CTX ctx = workerCtx;
 544
 545         // Sha256 result buffer
 546         uint32_t hashProofOfStake[8];
 547
 548         // Compute maximum possible target to filter out majority of obviously insufficient hashes
 549         CBigNum bnTargetPerCoinDay;
 550         bnTargetPerCoinDay.SetCompact(nBits);
 551
 552         uint256 nMaxTarget = (bnTargetPerCoinDay * bnValueIn * nStakeMaxAge / COIN / nOneDay).getuint256(),
 553             *pnHashProofOfStake = (uint256 *)&hashProofOfStake;
 554
 555         // Search forward in time from the given timestamp
 556         // Stopping search in case of shutting down
 557         for (uint32_t nTimeTx=nIntervalBegin, nMaxTarget32 = nMaxTarget.Get32(7); nTimeTx<nIntervalEnd && !fShutdown; nTimeTx++)
 558         {
 559             // Complete first hashing iteration
 560             uint256 hash1;
 561             SHA256_Update(&ctx, (unsigned char*)&nTimeTx, 4);
 562             SHA256_Final((unsigned char*)&hash1, &ctx);
 563
 564             // Restore context
 565             ctx = workerCtx;
 566
 567             // Finally, calculate kernel hash
 568             SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 569
 570             // Skip if hash doesn't satisfy the maximum target
 571             if (hashProofOfStake[7] > nMaxTarget32)
 572                 continue;
 573
 574             CBigNum bnCoinDayWeight = bnValueIn * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 575             CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 576
 577             if (bnTargetProofOfStake >= CBigNum(*pnHashProofOfStake))
 578                 solutions.push_back(std::pair<uint256,uint32_t>(*pnHashProofOfStake, nTimeTx));
 579         }
 580     }
 581
 582     vector<std::pair<uint256,uint32_t> >& GetSolutions()
 583     {
 584         return solutions;
 585     }
 586
 587 private:
 588     SHA256_CTX workerCtx;
 589     std::vector<std::pair<uint256,uint32_t> > solutions;
 590
 591     uint32_t nBits;
 592     uint32_t nInputTxTime;
 593     CBigNum  bnValueIn;
 594     uint32_t nIntervalBegin;
 595     uint32_t nIntervalEnd;
 596 };
 597
 598 #endif
 599 // Scan given kernel for solution
 600 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)
 601 {
 602     // TODO: custom threads amount
 603
 604     uint32_t nThreads = boost::thread::hardware_concurrency();
 605     uint32_t nPart = (SearchInterval.second - SearchInterval.first) / nThreads;
 606
 607
 608     ScanMidstateWorker *workers = new ScanMidstateWorker[nThreads];
 609
 610     boost::thread_group group;
 611     for(size_t i = 0; i < nThreads; i++)
 612     {
 613         uint32_t nBegin = SearchInterval.first + nPart * i;
 614         uint32_t nEnd = SearchInterval.first + nPart * (i + 1);
 615         workers[i] = ScanMidstateWorker(kernel, nBits, nInputTxTime, nValueIn, nBegin, nEnd);
 616         boost::function<void()> workerFnc = boost::bind(&ScanMidstateWorker::Do, &workers[i]);
 617         group.create_thread(workerFnc);
 618     }
 619
 620     group.join_all();
 621     solutions.clear();
 622
 623     for(size_t i = 0; i < nThreads; i++)
 624     {
 625         std::vector<std::pair<uint256, uint32_t> > ws = workers[i].GetSolutions();
 626         solutions.insert(solutions.end(), ws.begin(), ws.end());
 627     }
 628
 629     delete [] workers;
 630
 631     if (solutions.size() == 0)
 632     {
 633         // no solutions
 634         return false;
 635     }
 636
 637     return true;
 638 }
 639
 640 // Scan given midstate for solution
 641 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)
 642 {
 643     CBigNum bnTargetPerCoinDay;
 644     bnTargetPerCoinDay.SetCompact(nBits);
 645
 646     // Get maximum possible target to filter out the majority of obviously insufficient hashes
 647     CBigNum bnMaxTargetPerCoinDay = bnTargetPerCoinDay * CBigNum(nValueIn) * nStakeMaxAge / COIN / nOneDay;
 648     uint256 maxTarget = bnMaxTargetPerCoinDay.getuint256();
 649
 650     SHA256_CTX ctxCopy = ctx;
 651
 652     // Search backward in time from the given timestamp
 653     // Stopping search in case of shutting down
 654     for (uint32_t nTimeTx=SearchInterval.first; nTimeTx>SearchInterval.second && !fShutdown; nTimeTx--)
 655     {
 656         // Complete first hashing iteration
 657         uint256 hash1;
 658         SHA256_Update(&ctxCopy, (unsigned char*)&nTimeTx, 4);
 659         SHA256_Final((unsigned char*)&hash1, &ctxCopy);
 660
 661         // Restore context
 662         ctxCopy = ctx;
 663
 664         // Finally, calculate kernel hash
 665         uint256 hashProofOfStake;
 666         SHA256((unsigned char*)&hash1, sizeof(hashProofOfStake), (unsigned char*)&hashProofOfStake);
 667
 668         // Skip if hash doesn't satisfy the maximum target
 669         if (hashProofOfStake > maxTarget)
 670             continue;
 671
 672         CBigNum bnCoinDayWeight = CBigNum(nValueIn) * GetWeight((int64_t)nInputTxTime, (int64_t)nTimeTx) / COIN / nOneDay;
 673         CBigNum bnTargetProofOfStake = bnCoinDayWeight * bnTargetPerCoinDay;
 674
 675         if (bnTargetProofOfStake >= CBigNum(hashProofOfStake))
 676         {
 677             solution.first = hashProofOfStake;
 678             solution.second = nTimeTx;
 679
 680             return true;
 681         }
 682     }
 683
 684     return false;
 685 }
 686
 687 // Check kernel hash target and coinstake signature
 688 bool CheckProofOfStake(const CTransaction& tx, unsigned int nBits, uint256& hashProofOfStake, uint256& targetProofOfStake)
 689 {
 690     if (!tx.IsCoinStake())
 691         return error("CheckProofOfStake() : called on non-coinstake %s", tx.GetHash().ToString().c_str());
 692
 693     // Kernel (input 0) must match the stake hash target per coin age (nBits)
 694     const CTxIn& txin = tx.vin[0];
 695
 696     // First try finding the previous transaction in database
 697     CTxDB txdb("r");
 698     CTransaction txPrev;
 699     CTxIndex txindex;
 700     if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
 701         return tx.DoS(1, error("CheckProofOfStake() : INFO: read txPrev failed"));  // previous transaction not in main chain, may occur during initial download
 702
 703 #ifndef USE_LEVELDB
 704     txdb.Close();
 705 #endif
 706
 707     // Verify signature
 708     if (!VerifySignature(txPrev, tx, 0, MANDATORY_SCRIPT_VERIFY_FLAGS, 0))
 709         return tx.DoS(100, error("CheckProofOfStake() : VerifySignature failed on coinstake %s", tx.GetHash().ToString().c_str()));
 710
 711     // Read block header
 712     CBlock block;
 713     if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
 714         return fDebug? error("CheckProofOfStake() : read block failed") : false; // unable to read block of previous transaction
 715
 716     if (!CheckStakeKernelHash(nBits, block, txindex.pos.nTxPos - txindex.pos.nBlockPos, txPrev, txin.prevout, tx.nTime, hashProofOfStake, targetProofOfStake, fDebug))
 717         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
 718
 719     return true;
 720 }
 721
 722 // Get stake modifier checksum
 723 uint32_t GetStakeModifierChecksum(const CBlockIndex* pindex)
 724 {
 725     assert (pindex->pprev || pindex->GetBlockHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
 726     // Hash previous checksum with flags, hashProofOfStake and nStakeModifier
 727     CDataStream ss(SER_GETHASH, 0);
 728     if (pindex->pprev)
 729         ss << pindex->pprev->nStakeModifierChecksum;
 730     ss << pindex->nFlags << pindex->hashProofOfStake << pindex->nStakeModifier;
 731     uint256 hashChecksum = Hash(ss.begin(), ss.end());
 732     hashChecksum >>= (256 - 32);
 733     return static_cast<uint32_t>(hashChecksum.Get64());
 734 }
 735
 736 // Check stake modifier hard checkpoints
 737 bool CheckStakeModifierCheckpoints(int nHeight, uint32_t nStakeModifierChecksum)
 738 {
 739     MapModifierCheckpoints& checkpoints = (fTestNet ? mapStakeModifierCheckpointsTestNet : mapStakeModifierCheckpoints);
 740
 741     if (checkpoints.count(nHeight))
 742         return nStakeModifierChecksum == checkpoints[nHeight];
 743     return true;
 744 }