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65 lines
2.5 KiB
Go
65 lines
2.5 KiB
Go
package pow
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import (
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"math/big"
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"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
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"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
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"github.com/kaspanet/kaspad/domain/consensus/utils/hashes"
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"github.com/kaspanet/kaspad/domain/consensus/utils/serialization"
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"github.com/kaspanet/kaspad/util"
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"github.com/pkg/errors"
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)
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// CheckProofOfWorkWithTarget check's if the block has a valid PoW according to the provided target
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// it does not check if the difficulty itself is valid or less than the maximum for the appropriate network
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func CheckProofOfWorkWithTarget(header *externalapi.DomainBlockHeader, target *big.Int) bool {
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// The block pow must be less than the claimed target
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powNum := calcPowValue(header)
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// The block hash must be less or equal than the claimed target.
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return powNum.Cmp(target) <= 0
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}
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// CheckProofOfWorkByBits check's if the block has a valid PoW according to its Bits field
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// it does not check if the difficulty itself is valid or less than the maximum for the appropriate network
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func CheckProofOfWorkByBits(header *externalapi.DomainBlockHeader) bool {
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return CheckProofOfWorkWithTarget(header, util.CompactToBig(header.Bits))
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}
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func calcPowValue(header *externalapi.DomainBlockHeader) *big.Int {
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// Zero out the time and nonce.
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timestamp, nonce := header.TimeInMilliseconds, header.Nonce
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header.TimeInMilliseconds, header.Nonce = 0, 0
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prePowHash := consensushashing.HeaderHash(header)
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header.TimeInMilliseconds, header.Nonce = timestamp, nonce
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// PRE_POW_HASH || TIME || 32 zero byte padding || NONCE
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writer := hashes.NewPoWHashWriter()
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writer.InfallibleWrite(prePowHash[:])
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err := serialization.WriteElement(writer, timestamp)
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if err != nil {
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panic(errors.Wrap(err, "this should never happen. Hash digest should never return an error"))
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}
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zeroes := [32]byte{}
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writer.InfallibleWrite(zeroes[:])
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err = serialization.WriteElement(writer, nonce)
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if err != nil {
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panic(errors.Wrap(err, "this should never happen. Hash digest should never return an error"))
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}
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return toBig(writer.Finalize())
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}
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// ToBig converts a externalapi.DomainHash into a big.Int treated as a little endian string.
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func toBig(hash *externalapi.DomainHash) *big.Int {
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// We treat the Hash as little-endian for PoW purposes, but the big package wants the bytes in big-endian, so reverse them.
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buf := hash.Clone()
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blen := len(buf)
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for i := 0; i < blen/2; i++ {
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buf[i], buf[blen-1-i] = buf[blen-1-i], buf[i]
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}
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return new(big.Int).SetBytes(buf[:])
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}
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