package pow import ( "github.com/kaspanet/kaspad/domain/consensus/model/externalapi" "github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing" "github.com/kaspanet/kaspad/domain/consensus/utils/constants" "github.com/kaspanet/kaspad/domain/consensus/utils/hashes" "github.com/kaspanet/kaspad/domain/consensus/utils/serialization" "github.com/kaspanet/kaspad/util/difficulty" "github.com/pkg/errors" "math/big" ) // CheckProofOfWorkWithTarget check's if the block has a valid PoW according to the provided target // it does not check if the difficulty itself is valid or less than the maximum for the appropriate network func CheckProofOfWorkWithTarget(header externalapi.MutableBlockHeader, target *big.Int) bool { // The block pow must be less than the claimed target powNum := CalculateProofOfWorkValue(header) // The block hash must be less or equal than the claimed target. return powNum.Cmp(target) <= 0 } // CheckProofOfWorkByBits check's if the block has a valid PoW according to its Bits field // it does not check if the difficulty itself is valid or less than the maximum for the appropriate network func CheckProofOfWorkByBits(header externalapi.MutableBlockHeader) bool { return CheckProofOfWorkWithTarget(header, difficulty.CompactToBig(header.Bits())) } // CalculateProofOfWorkValue hashes the given header and returns its big.Int value func CalculateProofOfWorkValue(header externalapi.MutableBlockHeader) *big.Int { // Zero out the time and nonce. timestamp, nonce := header.TimeInMilliseconds(), header.Nonce() header.SetTimeInMilliseconds(0) header.SetNonce(0) prePowHash := consensushashing.HeaderHash(header) matrix := generateMatrix(prePowHash) header.SetTimeInMilliseconds(timestamp) header.SetNonce(nonce) // PRE_POW_HASH || TIME || 32 zero byte padding || NONCE writer := hashes.NewPoWHashWriter() writer.InfallibleWrite(prePowHash.ByteSlice()) err := serialization.WriteElement(writer, timestamp) if err != nil { panic(errors.Wrap(err, "this should never happen. Hash digest should never return an error")) } zeroes := [32]byte{} writer.InfallibleWrite(zeroes[:]) err = serialization.WriteElement(writer, nonce) if err != nil { panic(errors.Wrap(err, "this should never happen. Hash digest should never return an error")) } powHash := writer.Finalize() heavyHash := matrix.HeavyHash(powHash) return toBig(heavyHash) } // ToBig converts a externalapi.DomainHash into a big.Int treated as a little endian string. func toBig(hash *externalapi.DomainHash) *big.Int { // We treat the Hash as little-endian for PoW purposes, but the big package wants the bytes in big-endian, so reverse them. buf := hash.ByteSlice() blen := len(buf) for i := 0; i < blen/2; i++ { buf[i], buf[blen-1-i] = buf[blen-1-i], buf[i] } return new(big.Int).SetBytes(buf) } // BlockLevel returns the block level of the given header. func BlockLevel(header externalapi.BlockHeader) int { // Genesis is defined to be the root of all blocks at all levels, so we define it to be the maximal // block level. if len(header.DirectParents()) == 0 { return constants.MaxBlockLevel } proofOfWorkValue := CalculateProofOfWorkValue(header.ToMutable()) for blockLevel := 0; ; blockLevel++ { if blockLevel == constants.MaxBlockLevel || proofOfWorkValue.Bit(blockLevel+1) != 0 { return blockLevel } } }