use gnark API for Add

This commit is contained in:
Kevaundray Wedderburn 2024-10-14 14:51:18 +01:00
parent a65fe31842
commit 8eecf9fdad
2 changed files with 1 additions and 92 deletions

View file

@ -20,25 +20,7 @@ type G1 struct {
// Add adds `a` and `b` together storing the result in `g` // Add adds `a` and `b` together storing the result in `g`
func (g *G1) Add(a, b *G1) { func (g *G1) Add(a, b *G1) {
// TODO(Decision to be made): There are three ways to g.inner.Add(&a.inner, &b.inner)
// TODO do this addition. Each with different performance
// TODO: characteristics.
//
// Option 1: This just calls a method in gnark
// g.inner.Add(&a.inner, &b.inner)
// Option 2: This calls multiple methods in gnark
// but is faster.
//
// var res bn254.G1Jac
// res.FromAffine(&a.inner)
// res.AddMixed(&b.inner)
// g.inner.FromJacobian(&res)
// Option 3: This calls a method that I created that
// we can upstream to gnark.
// This should be the fastest, I can write the same for G2
g.addAffine(a, b)
} }
// ScalarMult computes the scalar multiplication between `a` and // ScalarMult computes the scalar multiplication between `a` and

View file

@ -1,73 +0,0 @@
package bn256
import (
"github.com/consensys/gnark-crypto/ecc/bn254/fp"
)
// This is just the addition formula
// but given we know that we do not need Jacobian
// coordinates, we use the naive implementation.
//
// Ideally, we push this into gnark
func (g *G1) addAffine(a_, b_ *G1) {
// Get the gnark specific points
var a = a_.inner
var b = b_.inner
// If a is 0, then return b
if a.IsInfinity() {
g.inner.Set(&b)
return
}
// If b is 0, then return a
if b.IsInfinity() {
g.inner.Set(&a)
return
}
// If a == -b, then return 0
g.inner.Neg(&b)
if a.Equal(&g.inner) {
g.inner.X.SetZero()
g.inner.Y.SetZero()
return
}
// Compute lambda based on whether we
// are doing a point addition or a point doubling
//
// Check if points are equal
var pointsAreEqual = a.Equal(&b)
var denominator fp.Element
var lambda fp.Element
// If a == b, then we need to compute lambda for double
// else we need to compute lambda for addition
if pointsAreEqual {
// Compute numerator
lambda.Square(&a.X)
fp.MulBy3(&lambda)
denominator.Add(&a.Y, &a.Y)
} else {
// Compute numerator
lambda.Sub(&b.Y, &a.Y)
denominator.Sub(&b.X, &a.X)
}
denominator.Inverse(&denominator)
lambda.Mul(&lambda, &denominator)
// Compute x_3 as lambda^2 - a_x - b_x
g.inner.X.Square(&lambda)
g.inner.X.Sub(&g.inner.X, &a.X)
g.inner.X.Sub(&g.inner.X, &b.X)
// Compute y as lambda * (a_x - x_3) - a_y
g.inner.Y.Sub(&a.X, &g.inner.X)
g.inner.Y.Mul(&g.inner.Y, &lambda)
g.inner.Y.Sub(&g.inner.Y, &a.Y)
}