/
ristretto_helpers.go
105 lines (84 loc) · 2.41 KB
/
ristretto_helpers.go
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package ed_ristretto
import (
"crypto/rand"
"errors"
"fmt"
r255 "github.com/gtank/ristretto255"
)
var maxTryTimes = 10
var oneBytes = [32]byte{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
func ScModInverse(a [32]byte) [32]byte {
aScalar, _ := BytesReduceToScalar(a[:])
aInv := new(r255.Scalar).Invert(aScalar)
var aInvBytes [32]byte
aInv.Encode(aInvBytes[:0])
return aInvBytes
}
// out = a * b + c
func ScMulAdd(out, a, b, c *[32]byte){
aScalar, _ := BytesReduceToScalar((*a)[:])
bScalar, _ := BytesReduceToScalar((*b)[:])
cScalar, _ := BytesReduceToScalar((*c)[:])
outScalar := new(r255.Scalar).Multiply(aScalar, bScalar)
outScalar = new(r255.Scalar).Add(outScalar, cScalar)
outScalar.Encode((*out)[:0])
}
func ScReduce(out *[32]byte, in *[64]byte){
outScalar, _ := BytesReduceToScalar((*in)[:])
outScalar.Encode((*out)[:0])
}
func ScAdd(out, a, b *[32]byte){
aScalar, _ := BytesReduceToScalar((*a)[:])
bScalar, _ := BytesReduceToScalar((*b)[:])
sum := new(r255.Scalar).Add(aScalar, bScalar)
sum.Encode((*out)[:0])
}
func ScSub(out, a, b *[32]byte){
aScalar, _ := BytesReduceToScalar((*a)[:])
bScalar, _ := BytesReduceToScalar((*b)[:])
sum := new(r255.Scalar).Subtract(aScalar, bScalar)
sum.Encode((*out)[:0])
}
func ScMul(out, a, b *[32]byte){
aScalar, _ := BytesReduceToScalar((*a)[:])
bScalar, _ := BytesReduceToScalar((*b)[:])
mul := new(r255.Scalar).Multiply(aScalar, bScalar)
mul.Encode((*out)[:0])
}
func ScalarOne() *r255.Scalar {
one, _ := BytesReduceToScalar(oneBytes[:])
return one
}
func BytesReduceToScalar(in []byte) (*r255.Scalar, error) {
if len(in) != 64 && len(in) != 32 {
return nil, errors.New("error, input byte array must be 32 or 64 length.")
}
var barr [64]byte
copy(barr[:], in[:])
rlt := new(r255.Scalar).FromUniformBytes(barr[:])
return rlt, nil
}
func NewRandomScalar() (*r255.Scalar, error) {
for i := 0; i < maxTryTimes; i++ {
s := [64]byte{}
_, err := rand.Read(s[:])
if err != nil {
continue
}
sc, err := BytesReduceToScalar(s[:])
if err != nil || sc.Equal(r255.NewScalar()) == 1 {
continue
}
return sc, nil
}
return nil, fmt.Errorf("error in generating new random scalar after try %d times", maxTryTimes)
}
func NewRandomScalarBytes() ([32]byte, error) {
var rlt [32]byte
rndScalar, err := NewRandomScalar()
if err == nil {
rndScalar.Encode(rlt[:0])
return rlt, nil
}
return rlt, err
}