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116 lines
3.7 KiB
Go
116 lines
3.7 KiB
Go
// Copyright (c) 2015-2021 The btcsuite developers
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// Copyright (c) 2015-2021 The Decred developers
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package btcec
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import (
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"fmt"
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secp "github.com/decred/dcrd/dcrec/secp256k1/v4"
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)
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// JacobianPoint is an element of the group formed by the secp256k1 curve in
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// Jacobian projective coordinates and thus represents a point on the curve.
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type JacobianPoint = secp.JacobianPoint
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// infinityPoint is the jacobian representation of the point at infinity.
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var infinityPoint JacobianPoint
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// MakeJacobianPoint returns a Jacobian point with the provided X, Y, and Z
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// coordinates.
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func MakeJacobianPoint(x, y, z *FieldVal) JacobianPoint {
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return secp.MakeJacobianPoint(x, y, z)
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}
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// AddNonConst adds the passed Jacobian points together and stores the result
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// in the provided result param in *non-constant* time.
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func AddNonConst(p1, p2, result *JacobianPoint) {
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secp.AddNonConst(p1, p2, result)
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}
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// DecompressY attempts to calculate the Y coordinate for the given X
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// coordinate such that the result pair is a point on the secp256k1 curve. It
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// adjusts Y based on the desired oddness and returns whether or not it was
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// successful since not all X coordinates are valid.
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//
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// The magnitude of the provided X coordinate field val must be a max of 8 for
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// a correct result. The resulting Y field val will have a max magnitude of 2.
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func DecompressY(x *FieldVal, odd bool, resultY *FieldVal) bool {
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return secp.DecompressY(x, odd, resultY)
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}
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// DoubleNonConst doubles the passed Jacobian point and stores the result in
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// the provided result parameter in *non-constant* time.
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//
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// NOTE: The point must be normalized for this function to return the correct
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// result. The resulting point will be normalized.
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func DoubleNonConst(p, result *JacobianPoint) {
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secp.DoubleNonConst(p, result)
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}
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// ScalarBaseMultNonConst multiplies k*G where G is the base point of the group
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// and k is a big endian integer. The result is stored in Jacobian coordinates
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// (x1, y1, z1).
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//
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// NOTE: The resulting point will be normalized.
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func ScalarBaseMultNonConst(k *ModNScalar, result *JacobianPoint) {
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secp.ScalarBaseMultNonConst(k, result)
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}
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// ScalarMultNonConst multiplies k*P where k is a big endian integer modulo the
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// curve order and P is a point in Jacobian projective coordinates and stores
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// the result in the provided Jacobian point.
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//
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// NOTE: The point must be normalized for this function to return the correct
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// result. The resulting point will be normalized.
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func ScalarMultNonConst(k *ModNScalar, point, result *JacobianPoint) {
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secp.ScalarMultNonConst(k, point, result)
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}
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// ParseJacobian parses a byte slice point as a secp.Publickey and returns the
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// pubkey as a JacobianPoint. If the nonce is a zero slice, the infinityPoint
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// is returned.
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func ParseJacobian(point []byte) (JacobianPoint, error) {
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var result JacobianPoint
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if len(point) != 33 {
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str := fmt.Sprintf("invalid nonce: invalid length: %v",
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len(point))
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return JacobianPoint{}, makeError(secp.ErrPubKeyInvalidLen, str)
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}
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if point[0] == 0x00 {
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return infinityPoint, nil
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}
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noncePk, err := secp.ParsePubKey(point)
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if err != nil {
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return JacobianPoint{}, err
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}
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noncePk.AsJacobian(&result)
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return result, nil
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}
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// JacobianToByteSlice converts the passed JacobianPoint to a Pubkey
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// and serializes that to a byte slice. If the JacobianPoint is the infinity
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// point, a zero slice is returned.
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func JacobianToByteSlice(point JacobianPoint) []byte {
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if point.X == infinityPoint.X && point.Y == infinityPoint.Y {
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return make([]byte, 33)
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}
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point.ToAffine()
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return NewPublicKey(
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&point.X, &point.Y,
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).SerializeCompressed()
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}
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// GeneratorJacobian sets the passed JacobianPoint to the Generator Point.
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func GeneratorJacobian(jacobian *JacobianPoint) {
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var k ModNScalar
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k.SetInt(1)
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ScalarBaseMultNonConst(&k, jacobian)
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}
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