plugeth-utils/restricted/crypto/bls12381/fp.go
2021-09-13 15:12:49 -05:00

168 lines
3.0 KiB
Go

// Copyright 2020 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package bls12381
import (
"errors"
"math/big"
)
func fromBytes(in []byte) (*fe, error) {
fe := &fe{}
if len(in) != 48 {
return nil, errors.New("input string should be equal 48 bytes")
}
fe.setBytes(in)
if !fe.isValid() {
return nil, errors.New("must be less than modulus")
}
toMont(fe, fe)
return fe, nil
}
func fromBig(in *big.Int) (*fe, error) {
fe := new(fe).setBig(in)
if !fe.isValid() {
return nil, errors.New("invalid input string")
}
toMont(fe, fe)
return fe, nil
}
func fromString(in string) (*fe, error) {
fe, err := new(fe).setString(in)
if err != nil {
return nil, err
}
if !fe.isValid() {
return nil, errors.New("invalid input string")
}
toMont(fe, fe)
return fe, nil
}
func toBytes(e *fe) []byte {
e2 := new(fe)
fromMont(e2, e)
return e2.bytes()
}
func toBig(e *fe) *big.Int {
e2 := new(fe)
fromMont(e2, e)
return e2.big()
}
func toString(e *fe) (s string) {
e2 := new(fe)
fromMont(e2, e)
return e2.string()
}
func toMont(c, a *fe) {
mul(c, a, r2)
}
func fromMont(c, a *fe) {
mul(c, a, &fe{1})
}
func exp(c, a *fe, e *big.Int) {
z := new(fe).set(r1)
for i := e.BitLen(); i >= 0; i-- {
mul(z, z, z)
if e.Bit(i) == 1 {
mul(z, z, a)
}
}
c.set(z)
}
func inverse(inv, e *fe) {
if e.isZero() {
inv.zero()
return
}
u := new(fe).set(&modulus)
v := new(fe).set(e)
s := &fe{1}
r := &fe{0}
var k int
var z uint64
var found = false
// Phase 1
for i := 0; i < 768; i++ {
if v.isZero() {
found = true
break
}
if u.isEven() {
u.div2(0)
s.mul2()
} else if v.isEven() {
v.div2(0)
z += r.mul2()
} else if u.cmp(v) == 1 {
lsubAssign(u, v)
u.div2(0)
laddAssign(r, s)
s.mul2()
} else {
lsubAssign(v, u)
v.div2(0)
laddAssign(s, r)
z += r.mul2()
}
k += 1
}
if !found {
inv.zero()
return
}
if k < 381 || k > 381+384 {
inv.zero()
return
}
if r.cmp(&modulus) != -1 || z > 0 {
lsubAssign(r, &modulus)
}
u.set(&modulus)
lsubAssign(u, r)
// Phase 2
for i := k; i < 384*2; i++ {
double(u, u)
}
inv.set(u)
}
func sqrt(c, a *fe) bool {
u, v := new(fe).set(a), new(fe)
exp(c, a, pPlus1Over4)
square(v, c)
return u.equal(v)
}
func isQuadraticNonResidue(elem *fe) bool {
result := new(fe)
exp(result, elem, pMinus1Over2)
return !result.isOne()
}