err := extendedGCD(a, m.nat) if err != nil { return x, false } if u.IsOne() == no { return x, false } return x.set(A), true } // GCDVarTime calculates x = GCD(a, b) where at least one of a or b is odd, and // both are non-zero. If GCDVarTime returns an error, x is not modified. // // The output will be resized to the size of the larger of a and b. func (x *Nat) GCDVarTime(a, b *Nat) (*Nat, error) { u, _, err := extendedGCD(a, b) if err != nil { return nil, err } return x.set(u), nil } // extendedGCD...