noble-secp256k1 is not handling properly the point at infinity

[Elli610]

the toAffine method encodes the point at infinity O in affine coordinates as (0, 0):

if ( this.equals(I)) return { x: 0n , y: 0n }; // fast - path for zero point

The code of fromAffine importing affine to projective is the following:

static fromAffine (p: AffinePoint) {
  return new Point (p.x , p.y , 1n) ;
}

As we can see, fromAffine does not check for (0, 0) to properly import O. This means that silent errors in the computation will occur when exporting and then importing O, which can happen with valid operations (such as (l − 1) · P + P where P is a point of order l).

A simple way to fix it:

static fromAffine (p: AffinePoint) {
  if ((p.x === 0n) && (p.y === 0n)) return new Point (0n , 1n , 0n);
  else return new Point (p.x , p.y , 1n) ;
}

Solved with @LeJamon

[paulmillr]

1. use triple equality
2. don’t usw the spaces around cases (formatting)

[Elli610]

1. use triple equality
2. don’t usw the spaces around cases (formatting)

done 👍🏻

[paulmillr]

Can you please revery all other formatting changes on other lines? Thanks.

[Elli610]

Can you please revery all other formatting changes on other lines? Thanks.

fixed