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78 lines
1.8 KiB
78 lines
1.8 KiB
package pow
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import (
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"bytes"
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"crypto/sha256"
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"encoding/binary"
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)
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func checkSha2BDay(proof []byte, nonce, data []byte, diff uint32) bool {
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if len(proof) != 24 {
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return false
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}
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prefix1 := proof[:8]
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prefix2 := proof[8:16]
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prefix3 := proof[16:]
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if bytes.Equal(prefix1, prefix2) || bytes.Equal(prefix2, prefix3) ||
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bytes.Equal(prefix1, prefix3) {
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return false
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}
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resBuf := make([]byte, 32)
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h := sha256.New()
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h.Write(prefix1)
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h.Write(data)
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h.Write(nonce)
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h.Sum(resBuf[:0])
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res1 := binary.BigEndian.Uint64(resBuf) & ((1 << diff) - 1)
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h.Reset()
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h.Write(prefix2)
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h.Write(data)
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h.Write(nonce)
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h.Sum(resBuf[:0])
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res2 := binary.BigEndian.Uint64(resBuf) & ((1 << diff) - 1)
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h.Reset()
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h.Write(prefix3)
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h.Write(data)
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h.Write(nonce)
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h.Sum(resBuf[:0])
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res3 := binary.BigEndian.Uint64(resBuf) & ((1 << diff) - 1)
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return res1 == res2 && res2 == res3
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}
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func fulfilSha2BDay(nonce []byte, diff uint32, data []byte) []byte {
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// TODO make multithreaded if the difficulty is high enough.
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// For light proof-of-work requests, the overhead of parallelizing is
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// not worth it.
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type Pair struct {
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First, Second uint64
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}
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var i uint64 = 1
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prefix := make([]byte, 8)
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resBuf := make([]byte, 32)
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lut := make(map[uint64]Pair)
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h := sha256.New()
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for {
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binary.BigEndian.PutUint64(prefix, i)
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h.Write(prefix)
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h.Write(data)
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h.Write(nonce)
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h.Sum(resBuf[:0])
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res := binary.BigEndian.Uint64(resBuf) & ((1 << diff) - 1)
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pair, ok := lut[res]
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if ok {
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if pair.Second != 0 {
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ret := make([]byte, 24)
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binary.BigEndian.PutUint64(ret, pair.First)
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binary.BigEndian.PutUint64(ret[8:], pair.Second)
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copy(ret[16:], prefix)
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return ret
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}
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lut[res] = Pair{First: pair.First, Second: i}
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} else {
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lut[res] = Pair{First: i}
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}
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h.Reset()
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i++
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}
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}
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