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Use div-free EC power selection function

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License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protocol.ai>
This commit is contained in:
Jakub Sztandera 2019-10-28 20:01:10 +01:00
parent 6f73e8bf2f
commit 563c0e494e
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GPG Key ID: 9A9AF56F8B3879BA
2 changed files with 14 additions and 8 deletions
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21
chain/types/blockheader.go
View File

@ -3,11 +3,11 @@ package types
import (
"bytes"
"context"
"crypto/sha256"
"math/big"
block "github.com/ipfs/go-block-format"
"github.com/ipfs/go-cid"
"github.com/minio/sha256-simd"
"github.com/multiformats/go-multihash"
"go.opencensus.io/trace"
xerrors "golang.org/x/xerrors"
@ -166,19 +166,24 @@ func PowerCmp(eproof ElectionProof, mpow, totpow BigInt) bool {
/*
Need to check that
h(vrfout) / 2^256 < minerPower / totalPower
h(vrfout) / max(h) * e < minerPower / totalPower
max(h) == 2^256-1
which in terms of integer math means:
h(vrfout) * totalPower * e < minerPower * (2^256-1)
*/
h := sha256.Sum256(eproof)
// 2^256
rden := BigInt{big.NewInt(0).Exp(big.NewInt(2), big.NewInt(256), nil)}
lhs := BigFromBytes(h[:]).Int
lhs = lhs.Mul(lhs, blocksPerEpoch.Int)
lhs = lhs.Mul(lhs, totpow.Int)
top := BigMul(BigMul(rden, mpow), blocksPerEpoch)
out := BigDiv(top, totpow)
// rhs = minerPower * 2^256 - minerPower
// rhs = minerPower << 256 - minerPower
rhs := new(big.Int).Lsh(mpow.Int, 256)
rhs = rhs.Sub(rhs, mpow.Int)
hp := BigFromBytes(h[:])
return hp.LessThan(out)
return lhs.Cmp(rhs) == -1
}
func (t *Ticket) Equals(ot *Ticket) bool {

1
go.mod
View File

@ -61,6 +61,7 @@ require (
github.com/mattn/go-runewidth v0.0.4 // indirect
github.com/miekg/dns v1.1.16 // indirect
github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1
github.com/minio/sha256-simd v0.1.0
github.com/mitchellh/go-homedir v1.1.0
github.com/multiformats/go-base32 v0.0.3
github.com/multiformats/go-multiaddr v0.0.4