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crypto/bn256: full switchover to cloudflare's code (#16301)

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* crypto/bn256: full switchover to cloudflare's code

* crypto/bn256: only use cloudflare for optimized architectures

* crypto/bn256: upstream fallback for non-optimized code

* .travis, build: drop support for Go 1.8 (need type aliases)

* crypto/bn256/cloudflare: enable curve mul lattice optimization
This commit is contained in:
Péter Szilágyi
2018-03-20 01:13:54 +09:00
committed by GitHub
parent 0965761a45
commit 1203c6a237
22 changed files with 783 additions and 174 deletions
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21
crypto/bn256/cloudflare/curve.go
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@ -183,15 +183,24 @@ func (c *curvePoint) Double(a *curvePoint) {
}
func (c *curvePoint) Mul(a *curvePoint, scalar *big.Int) {
sum, t := &curvePoint{}, &curvePoint{}
sum.SetInfinity()
precomp := [1 << 2]*curvePoint{nil, {}, {}, {}}
precomp[1].Set(a)
precomp[2].Set(a)
gfpMul(&precomp[2].x, &precomp[2].x, xiTo2PSquaredMinus2Over3)
precomp[3].Add(precomp[1], precomp[2])
for i := scalar.BitLen(); i >= 0; i-- {
multiScalar := curveLattice.Multi(scalar)
sum := &curvePoint{}
sum.SetInfinity()
t := &curvePoint{}
for i := len(multiScalar) - 1; i >= 0; i-- {
t.Double(sum)
if scalar.Bit(i) != 0 {
sum.Add(t, a)
} else {
if multiScalar[i] == 0 {
sum.Set(t)
} else {
sum.Add(t, precomp[multiScalar[i]])
}
}
c.Set(sum)