/
point.go
127 lines (108 loc) · 3.43 KB
/
point.go
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/*
* Copyright (C) 2015-2019 Virgil Security Inc.
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* (1) Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* (2) Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* (3) Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Lead Maintainer: Virgil Security Inc. <support@virgilsecurity.com>
*/
package phe
import (
"crypto/elliptic"
"math/big"
"github.com/pkg/errors"
)
// Point represents an elliptic curve point
type Point struct {
X, Y *big.Int
}
var (
pn = curve.Params().P
zero = big.NewInt(0)
)
// PointUnmarshal validates & converts byte array to an elliptic curve point object
func PointUnmarshal(data []byte) (*Point, error) {
if len(data) != 65 {
return nil, errors.New("Invalid curve point")
}
x, y := elliptic.Unmarshal(curve, data)
if x == nil || y == nil {
return nil, errors.New("Invalid curve point")
}
return &Point{
X: x,
Y: y,
}, nil
}
// Add adds two points
func (p *Point) Add(a *Point) *Point {
x, y := curve.Add(p.X, p.Y, a.X, a.Y)
return &Point{x, y}
}
// Neg inverts point's Y coordinate
func (p *Point) Neg() *Point {
t := new(Point)
t.X = p.X
t.Y = new(big.Int).Sub(pn, p.Y)
return t
}
// ScalarMult multiplies point to a number
func (p *Point) ScalarMult(b []byte) *Point {
x, y := curve.ScalarMult(p.X, p.Y, b)
return &Point{x, y}
}
// ScalarMultInt multiplies point to a number
func (p *Point) ScalarMultInt(b *big.Int) *Point {
x, y := curve.ScalarMult(p.X, p.Y, b.Bytes())
return &Point{x, y}
}
// ScalarBaseMult multiplies base point to a number
func (p *Point) ScalarBaseMult(b []byte) *Point {
x, y := curve.ScalarBaseMult(b)
return &Point{x, y}
}
// ScalarBaseMultInt multiplies base point to a number
func (p *Point) ScalarBaseMultInt(b *big.Int) *Point {
x, y := curve.ScalarBaseMult(b.Bytes())
return &Point{x, y}
}
// Marshal converts point to an array of bytes
func (p *Point) Marshal() []byte {
if p.X.Cmp(zero) != 0 &&
p.Y.Cmp(zero) != 0 {
return elliptic.Marshal(curve, p.X, p.Y)
}
panic("zero point")
}
// Equal checks two points for equality
func (p *Point) Equal(other *Point) bool {
return p.X.Cmp(other.X) == 0 &&
p.Y.Cmp(other.Y) == 0
}