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crypto/secp256k1: update function receiver variable name to lower-case style #29889

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May 30, 2024
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crypto/secp256k1: update function receiver variable name to lower-case style #29889

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88 changes: 44 additions & 44 deletions crypto/secp256k1/curve.go
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Original file line number Diff line number Diff line change
Expand Up @@ -79,52 +79,52 @@ type BitCurve struct {
BitSize int // the size of the underlying field
}

func (BitCurve *BitCurve) Params() *elliptic.CurveParams {
func (bitCurve *BitCurve) Params() *elliptic.CurveParams {
return &elliptic.CurveParams{
P: BitCurve.P,
N: BitCurve.N,
B: BitCurve.B,
Gx: BitCurve.Gx,
Gy: BitCurve.Gy,
BitSize: BitCurve.BitSize,
P: bitCurve.P,
N: bitCurve.N,
B: bitCurve.B,
Gx: bitCurve.Gx,
Gy: bitCurve.Gy,
BitSize: bitCurve.BitSize,
}
}

// IsOnCurve returns true if the given (x,y) lies on the BitCurve.
func (BitCurve *BitCurve) IsOnCurve(x, y *big.Int) bool {
func (bitCurve *BitCurve) IsOnCurve(x, y *big.Int) bool {
// y² = x³ + b
y2 := new(big.Int).Mul(y, y) //y²
y2.Mod(y2, BitCurve.P) //y²%P
y2.Mod(y2, bitCurve.P) //y²%P

x3 := new(big.Int).Mul(x, x) //x²
x3.Mul(x3, x) //x³

x3.Add(x3, BitCurve.B) //x³+B
x3.Mod(x3, BitCurve.P) //(x³+B)%P
x3.Add(x3, bitCurve.B) //x³+B
x3.Mod(x3, bitCurve.P) //(x³+B)%P

return x3.Cmp(y2) == 0
}

// affineFromJacobian reverses the Jacobian transform. See the comment at the
// top of the file.
func (BitCurve *BitCurve) affineFromJacobian(x, y, z *big.Int) (xOut, yOut *big.Int) {
func (bitCurve *BitCurve) affineFromJacobian(x, y, z *big.Int) (xOut, yOut *big.Int) {
if z.Sign() == 0 {
return new(big.Int), new(big.Int)
}

zinv := new(big.Int).ModInverse(z, BitCurve.P)
zinv := new(big.Int).ModInverse(z, bitCurve.P)
zinvsq := new(big.Int).Mul(zinv, zinv)

xOut = new(big.Int).Mul(x, zinvsq)
xOut.Mod(xOut, BitCurve.P)
xOut.Mod(xOut, bitCurve.P)
zinvsq.Mul(zinvsq, zinv)
yOut = new(big.Int).Mul(y, zinvsq)
yOut.Mod(yOut, BitCurve.P)
yOut.Mod(yOut, bitCurve.P)
return
}

// Add returns the sum of (x1,y1) and (x2,y2)
func (BitCurve *BitCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int) {
func (bitCurve *BitCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int) {
// If one point is at infinity, return the other point.
// Adding the point at infinity to any point will preserve the other point.
if x1.Sign() == 0 && y1.Sign() == 0 {
Expand All @@ -135,41 +135,41 @@ func (BitCurve *BitCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int) {
}
z := new(big.Int).SetInt64(1)
if x1.Cmp(x2) == 0 && y1.Cmp(y2) == 0 {
return BitCurve.affineFromJacobian(BitCurve.doubleJacobian(x1, y1, z))
return bitCurve.affineFromJacobian(bitCurve.doubleJacobian(x1, y1, z))
}
return BitCurve.affineFromJacobian(BitCurve.addJacobian(x1, y1, z, x2, y2, z))
return bitCurve.affineFromJacobian(bitCurve.addJacobian(x1, y1, z, x2, y2, z))
}

// addJacobian takes two points in Jacobian coordinates, (x1, y1, z1) and
// (x2, y2, z2) and returns their sum, also in Jacobian form.
func (BitCurve *BitCurve) addJacobian(x1, y1, z1, x2, y2, z2 *big.Int) (*big.Int, *big.Int, *big.Int) {
func (bitCurve *BitCurve) addJacobian(x1, y1, z1, x2, y2, z2 *big.Int) (*big.Int, *big.Int, *big.Int) {
// See http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#addition-add-2007-bl
z1z1 := new(big.Int).Mul(z1, z1)
z1z1.Mod(z1z1, BitCurve.P)
z1z1.Mod(z1z1, bitCurve.P)
z2z2 := new(big.Int).Mul(z2, z2)
z2z2.Mod(z2z2, BitCurve.P)
z2z2.Mod(z2z2, bitCurve.P)

u1 := new(big.Int).Mul(x1, z2z2)
u1.Mod(u1, BitCurve.P)
u1.Mod(u1, bitCurve.P)
u2 := new(big.Int).Mul(x2, z1z1)
u2.Mod(u2, BitCurve.P)
u2.Mod(u2, bitCurve.P)
h := new(big.Int).Sub(u2, u1)
if h.Sign() == -1 {
h.Add(h, BitCurve.P)
h.Add(h, bitCurve.P)
}
i := new(big.Int).Lsh(h, 1)
i.Mul(i, i)
j := new(big.Int).Mul(h, i)

s1 := new(big.Int).Mul(y1, z2)
s1.Mul(s1, z2z2)
s1.Mod(s1, BitCurve.P)
s1.Mod(s1, bitCurve.P)
s2 := new(big.Int).Mul(y2, z1)
s2.Mul(s2, z1z1)
s2.Mod(s2, BitCurve.P)
s2.Mod(s2, bitCurve.P)
r := new(big.Int).Sub(s2, s1)
if r.Sign() == -1 {
r.Add(r, BitCurve.P)
r.Add(r, bitCurve.P)
}
r.Lsh(r, 1)
v := new(big.Int).Mul(u1, i)
Expand All @@ -179,41 +179,41 @@ func (BitCurve *BitCurve) addJacobian(x1, y1, z1, x2, y2, z2 *big.Int) (*big.Int
x3.Sub(x3, j)
x3.Sub(x3, v)
x3.Sub(x3, v)
x3.Mod(x3, BitCurve.P)
x3.Mod(x3, bitCurve.P)

y3 := new(big.Int).Set(r)
v.Sub(v, x3)
y3.Mul(y3, v)
s1.Mul(s1, j)
s1.Lsh(s1, 1)
y3.Sub(y3, s1)
y3.Mod(y3, BitCurve.P)
y3.Mod(y3, bitCurve.P)

z3 := new(big.Int).Add(z1, z2)
z3.Mul(z3, z3)
z3.Sub(z3, z1z1)
if z3.Sign() == -1 {
z3.Add(z3, BitCurve.P)
z3.Add(z3, bitCurve.P)
}
z3.Sub(z3, z2z2)
if z3.Sign() == -1 {
z3.Add(z3, BitCurve.P)
z3.Add(z3, bitCurve.P)
}
z3.Mul(z3, h)
z3.Mod(z3, BitCurve.P)
z3.Mod(z3, bitCurve.P)

return x3, y3, z3
}

// Double returns 2*(x,y)
func (BitCurve *BitCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int) {
func (bitCurve *BitCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int) {
z1 := new(big.Int).SetInt64(1)
return BitCurve.affineFromJacobian(BitCurve.doubleJacobian(x1, y1, z1))
return bitCurve.affineFromJacobian(bitCurve.doubleJacobian(x1, y1, z1))
}

// doubleJacobian takes a point in Jacobian coordinates, (x, y, z), and
// returns its double, also in Jacobian form.
func (BitCurve *BitCurve) doubleJacobian(x, y, z *big.Int) (*big.Int, *big.Int, *big.Int) {
func (bitCurve *BitCurve) doubleJacobian(x, y, z *big.Int) (*big.Int, *big.Int, *big.Int) {
// See http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#doubling-dbl-2009-l

a := new(big.Int).Mul(x, x) //X1²
Expand All @@ -231,30 +231,30 @@ func (BitCurve *BitCurve) doubleJacobian(x, y, z *big.Int) (*big.Int, *big.Int,

x3 := new(big.Int).Mul(big.NewInt(2), d) //2*D
x3.Sub(f, x3) //F-2*D
x3.Mod(x3, BitCurve.P)
x3.Mod(x3, bitCurve.P)

y3 := new(big.Int).Sub(d, x3) //D-X3
y3.Mul(e, y3) //E*(D-X3)
y3.Sub(y3, new(big.Int).Mul(big.NewInt(8), c)) //E*(D-X3)-8*C
y3.Mod(y3, BitCurve.P)
y3.Mod(y3, bitCurve.P)

z3 := new(big.Int).Mul(y, z) //Y1*Z1
z3.Mul(big.NewInt(2), z3) //3*Y1*Z1
z3.Mod(z3, BitCurve.P)
z3.Mod(z3, bitCurve.P)

return x3, y3, z3
}

// ScalarBaseMult returns k*G, where G is the base point of the group and k is
// an integer in big-endian form.
func (BitCurve *BitCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int) {
return BitCurve.ScalarMult(BitCurve.Gx, BitCurve.Gy, k)
func (bitCurve *BitCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int) {
return bitCurve.ScalarMult(bitCurve.Gx, bitCurve.Gy, k)
}

// Marshal converts a point into the form specified in section 4.3.6 of ANSI
// X9.62.
func (BitCurve *BitCurve) Marshal(x, y *big.Int) []byte {
byteLen := (BitCurve.BitSize + 7) >> 3
func (bitCurve *BitCurve) Marshal(x, y *big.Int) []byte {
byteLen := (bitCurve.BitSize + 7) >> 3
ret := make([]byte, 1+2*byteLen)
ret[0] = 4 // uncompressed point flag
readBits(x, ret[1:1+byteLen])
Expand All @@ -264,8 +264,8 @@ func (BitCurve *BitCurve) Marshal(x, y *big.Int) []byte {

// Unmarshal converts a point, serialised by Marshal, into an x, y pair. On
// error, x = nil.
func (BitCurve *BitCurve) Unmarshal(data []byte) (x, y *big.Int) {
byteLen := (BitCurve.BitSize + 7) >> 3
func (bitCurve *BitCurve) Unmarshal(data []byte) (x, y *big.Int) {
byteLen := (bitCurve.BitSize + 7) >> 3
if len(data) != 1+2*byteLen {
return
}
Expand Down
2 changes: 1 addition & 1 deletion crypto/secp256k1/scalar_mult_cgo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ extern int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, const unsigned
*/
import "C"

func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int) {
func (bitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int) {
// Ensure scalar is exactly 32 bytes. We pad always, even if
// scalar is 32 bytes long, to avoid a timing side channel.
if len(scalar) > 32 {
Expand Down
2 changes: 1 addition & 1 deletion crypto/secp256k1/scalar_mult_nocgo.go
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Expand Up @@ -9,6 +9,6 @@ package secp256k1

import "math/big"

func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int) {
func (bitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int) {
panic("ScalarMult is not available when secp256k1 is built without cgo")
}