181 lines
6.4 KiB
C++
181 lines
6.4 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2014 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or https://www.opensource.org/licenses/mit-license.php .
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#include "pow.h"
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#include "arith_uint256.h"
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#include "chain.h"
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#include "chainparams.h"
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#include "crypto/equihash.h"
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#include "primitives/block.h"
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#include "streams.h"
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#include "uint256.h"
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#include "util.h"
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#include "sodium.h"
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unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
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{
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unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
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// Genesis block
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if (pindexLast == NULL)
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return nProofOfWorkLimit;
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{
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// Comparing to pindexLast->nHeight with >= because this function
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// returns the work required for the block after pindexLast.
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if (params.nPowAllowMinDifficultyBlocksAfterHeight != boost::none &&
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pindexLast->nHeight >= params.nPowAllowMinDifficultyBlocksAfterHeight.get())
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{
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// Special difficulty rule for testnet:
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// If the new block's timestamp is more than 6 * block interval minutes
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// then allow mining of a min-difficulty block.
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if (pblock && pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.PoWTargetSpacing(pindexLast->nHeight + 1) * 6)
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return nProofOfWorkLimit;
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}
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}
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// Find the first block in the averaging interval
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const CBlockIndex* pindexFirst = pindexLast;
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arith_uint256 bnTot {0};
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for (int i = 0; pindexFirst && i < params.nPowAveragingWindow; i++) {
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arith_uint256 bnTmp;
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bnTmp.SetCompact(pindexFirst->nBits);
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bnTot += bnTmp;
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pindexFirst = pindexFirst->pprev;
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}
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// Check we have enough blocks
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if (pindexFirst == NULL)
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return nProofOfWorkLimit;
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arith_uint256 bnAvg {bnTot / params.nPowAveragingWindow};
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return CalculateNextWorkRequired(bnAvg,
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pindexLast->GetMedianTimePast(), pindexFirst->GetMedianTimePast(),
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params,
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pindexLast->nHeight + 1);
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}
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unsigned int CalculateNextWorkRequired(arith_uint256 bnAvg,
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int64_t nLastBlockTime, int64_t nFirstBlockTime,
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const Consensus::Params& params,
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int nextHeight)
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{
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int64_t averagingWindowTimespan = params.AveragingWindowTimespan(nextHeight);
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int64_t minActualTimespan = params.MinActualTimespan(nextHeight);
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int64_t maxActualTimespan = params.MaxActualTimespan(nextHeight);
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// Limit adjustment step
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// Use medians to prevent time-warp attacks
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int64_t nActualTimespan = nLastBlockTime - nFirstBlockTime;
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LogPrint("pow", " nActualTimespan = %d before dampening\n", nActualTimespan);
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nActualTimespan = averagingWindowTimespan + (nActualTimespan - averagingWindowTimespan)/4;
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LogPrint("pow", " nActualTimespan = %d before bounds\n", nActualTimespan);
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if (nActualTimespan < minActualTimespan) {
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nActualTimespan = minActualTimespan;
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}
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if (nActualTimespan > maxActualTimespan) {
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nActualTimespan = maxActualTimespan;
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}
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// Retarget
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const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
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arith_uint256 bnNew {bnAvg};
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bnNew /= averagingWindowTimespan;
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bnNew *= nActualTimespan;
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if (bnNew > bnPowLimit) {
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bnNew = bnPowLimit;
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}
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/// debug print
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LogPrint("pow", "GetNextWorkRequired RETARGET\n");
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LogPrint("pow", "params.AveragingWindowTimespan(%d) = %d nActualTimespan = %d\n", nextHeight, averagingWindowTimespan, nActualTimespan);
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LogPrint("pow", "Current average: %08x %s\n", bnAvg.GetCompact(), bnAvg.ToString());
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LogPrint("pow", "After: %08x %s\n", bnNew.GetCompact(), bnNew.ToString());
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return bnNew.GetCompact();
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}
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bool CheckEquihashSolution(const CBlockHeader *pblock, const Consensus::Params& params)
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{
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unsigned int n = params.nEquihashN;
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unsigned int k = params.nEquihashK;
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// Hash state
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crypto_generichash_blake2b_state state;
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EhInitialiseState(n, k, state);
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// I = the block header minus nonce and solution.
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CEquihashInput I{*pblock};
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// I||V
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CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
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ss << I;
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ss << pblock->nNonce;
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// H(I||V||...
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crypto_generichash_blake2b_update(&state, (unsigned char*)&ss[0], ss.size());
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bool isValid;
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EhIsValidSolution(n, k, state, pblock->nSolution, isValid);
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if (!isValid)
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return error("CheckEquihashSolution(): invalid solution");
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return true;
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}
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bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params& params)
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{
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bool fNegative;
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bool fOverflow;
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arith_uint256 bnTarget;
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bnTarget.SetCompact(nBits, &fNegative, &fOverflow);
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// Check range
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if (fNegative || bnTarget == 0 || fOverflow || bnTarget > UintToArith256(params.powLimit))
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return error("CheckProofOfWork(): nBits below minimum work");
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// Check proof of work matches claimed amount
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if (UintToArith256(hash) > bnTarget)
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return error("CheckProofOfWork(): hash doesn't match nBits");
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return true;
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}
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arith_uint256 GetBlockProof(const CBlockIndex& block)
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{
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arith_uint256 bnTarget;
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bool fNegative;
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bool fOverflow;
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bnTarget.SetCompact(block.nBits, &fNegative, &fOverflow);
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if (fNegative || fOverflow || bnTarget == 0)
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return 0;
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// We need to compute 2**256 / (bnTarget+1), but we can't represent 2**256
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// as it's too large for a arith_uint256. However, as 2**256 is at least as large
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// as bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
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// or ~bnTarget / (nTarget+1) + 1.
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return (~bnTarget / (bnTarget + 1)) + 1;
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}
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int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params& params)
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{
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arith_uint256 r;
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int sign = 1;
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if (to.nChainWork > from.nChainWork) {
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r = to.nChainWork - from.nChainWork;
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} else {
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r = from.nChainWork - to.nChainWork;
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sign = -1;
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}
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r = r * arith_uint256(params.PoWTargetSpacing(tip.nHeight)) / GetBlockProof(tip);
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if (r.bits() > 63) {
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return sign * std::numeric_limits<int64_t>::max();
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}
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return sign * r.GetLow64();
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}
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