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Merge pull request #513 from steven004/Refactor-PowerCmp

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Refactor the PowerCmp function
This commit is contained in:
Łukasz Magiera 2019-11-09 00:59:10 +01:00 committed by GitHub
commit ee2cf48566
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1 changed files with 8 additions and 6 deletions
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14
chain/types/blockheader.go
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@ -166,10 +166,12 @@ func PowerCmp(eproof ElectionProof, mpow, totpow BigInt) bool {
/*
Need to check that
h(vrfout) / max(h) < e * minerPower / totalPower
(h(vrfout) + 1) / (max(h) + 1) <= e * minerPower / totalPower
max(h) == 2^256-1
which in terms of integer math means:
h(vrfout) * totalPower < e * minerPower * (2^256-1)
(h(vrfout) + 1) * totalPower <= e * minerPower * 2^256
in 2^256 space, it is equivalent to:
h(vrfout) * totalPower < e * minerPower * 2^256
*/
h := sha256.Sum256(eproof)
@ -177,12 +179,12 @@ func PowerCmp(eproof ElectionProof, mpow, totpow BigInt) bool {
lhs := BigFromBytes(h[:]).Int
lhs = lhs.Mul(lhs, totpow.Int)
// rhs = minerPower * 2^256 - minerPower
// rhs = minerPower << 256 - minerPower
// rhs = minerPower * 2^256
// rhs = minerPower << 256
rhs := new(big.Int).Lsh(mpow.Int, 256)
rhs = rhs.Mul(rhs, blocksPerEpoch.Int)
rhs = rhs.Sub(rhs, mpow.Int)
// h(vrfout) * totalPower < e * minerPower * 2^256?
return lhs.Cmp(rhs) == -1
}