mirror of
https://gitlab.com/pulsechaincom/go-pulse.git
synced 2024-12-24 20:37:17 +00:00
1203c6a237
* 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
116 lines
3.2 KiB
Go
116 lines
3.2 KiB
Go
package bn256
|
|
|
|
import (
|
|
"math/big"
|
|
)
|
|
|
|
var half = new(big.Int).Rsh(Order, 1)
|
|
|
|
var curveLattice = &lattice{
|
|
vectors: [][]*big.Int{
|
|
{bigFromBase10("147946756881789319000765030803803410728"), bigFromBase10("147946756881789319010696353538189108491")},
|
|
{bigFromBase10("147946756881789319020627676272574806254"), bigFromBase10("-147946756881789318990833708069417712965")},
|
|
},
|
|
inverse: []*big.Int{
|
|
bigFromBase10("147946756881789318990833708069417712965"),
|
|
bigFromBase10("147946756881789319010696353538189108491"),
|
|
},
|
|
det: bigFromBase10("43776485743678550444492811490514550177096728800832068687396408373151616991234"),
|
|
}
|
|
|
|
var targetLattice = &lattice{
|
|
vectors: [][]*big.Int{
|
|
{bigFromBase10("9931322734385697761"), bigFromBase10("9931322734385697761"), bigFromBase10("9931322734385697763"), bigFromBase10("9931322734385697764")},
|
|
{bigFromBase10("4965661367192848881"), bigFromBase10("4965661367192848881"), bigFromBase10("4965661367192848882"), bigFromBase10("-9931322734385697762")},
|
|
{bigFromBase10("-9931322734385697762"), bigFromBase10("-4965661367192848881"), bigFromBase10("4965661367192848881"), bigFromBase10("-4965661367192848882")},
|
|
{bigFromBase10("9931322734385697763"), bigFromBase10("-4965661367192848881"), bigFromBase10("-4965661367192848881"), bigFromBase10("-4965661367192848881")},
|
|
},
|
|
inverse: []*big.Int{
|
|
bigFromBase10("734653495049373973658254490726798021314063399421879442165"),
|
|
bigFromBase10("147946756881789319000765030803803410728"),
|
|
bigFromBase10("-147946756881789319005730692170996259609"),
|
|
bigFromBase10("1469306990098747947464455738335385361643788813749140841702"),
|
|
},
|
|
det: new(big.Int).Set(Order),
|
|
}
|
|
|
|
type lattice struct {
|
|
vectors [][]*big.Int
|
|
inverse []*big.Int
|
|
det *big.Int
|
|
}
|
|
|
|
// decompose takes a scalar mod Order as input and finds a short, positive decomposition of it wrt to the lattice basis.
|
|
func (l *lattice) decompose(k *big.Int) []*big.Int {
|
|
n := len(l.inverse)
|
|
|
|
// Calculate closest vector in lattice to <k,0,0,...> with Babai's rounding.
|
|
c := make([]*big.Int, n)
|
|
for i := 0; i < n; i++ {
|
|
c[i] = new(big.Int).Mul(k, l.inverse[i])
|
|
round(c[i], l.det)
|
|
}
|
|
|
|
// Transform vectors according to c and subtract <k,0,0,...>.
|
|
out := make([]*big.Int, n)
|
|
temp := new(big.Int)
|
|
|
|
for i := 0; i < n; i++ {
|
|
out[i] = new(big.Int)
|
|
|
|
for j := 0; j < n; j++ {
|
|
temp.Mul(c[j], l.vectors[j][i])
|
|
out[i].Add(out[i], temp)
|
|
}
|
|
|
|
out[i].Neg(out[i])
|
|
out[i].Add(out[i], l.vectors[0][i]).Add(out[i], l.vectors[0][i])
|
|
}
|
|
out[0].Add(out[0], k)
|
|
|
|
return out
|
|
}
|
|
|
|
func (l *lattice) Precompute(add func(i, j uint)) {
|
|
n := uint(len(l.vectors))
|
|
total := uint(1) << n
|
|
|
|
for i := uint(0); i < n; i++ {
|
|
for j := uint(0); j < total; j++ {
|
|
if (j>>i)&1 == 1 {
|
|
add(i, j)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
func (l *lattice) Multi(scalar *big.Int) []uint8 {
|
|
decomp := l.decompose(scalar)
|
|
|
|
maxLen := 0
|
|
for _, x := range decomp {
|
|
if x.BitLen() > maxLen {
|
|
maxLen = x.BitLen()
|
|
}
|
|
}
|
|
|
|
out := make([]uint8, maxLen)
|
|
for j, x := range decomp {
|
|
for i := 0; i < maxLen; i++ {
|
|
out[i] += uint8(x.Bit(i)) << uint(j)
|
|
}
|
|
}
|
|
|
|
return out
|
|
}
|
|
|
|
// round sets num to num/denom rounded to the nearest integer.
|
|
func round(num, denom *big.Int) {
|
|
r := new(big.Int)
|
|
num.DivMod(num, denom, r)
|
|
|
|
if r.Cmp(half) == 1 {
|
|
num.Add(num, big.NewInt(1))
|
|
}
|
|
}
|