section. y, err := new(field.Element).SetBytes(x) if err != nil { return nil, errors.New("edwards25519: invalid point encoding length") } // -x² + y² = 1 + dx²y² // x² + dx²y² = x²(dy² + 1) = y² - 1 // x² = (y² - 1) / (dy² + 1) // u = y² - 1 y2 := new(field.Element).Square(y) u := new(field.Element).Subtract(y2, feOne) // v = dy² + 1 vv := new(field.Element).Multiply(y2, d) vv = vv.Add(vv, feOne) // x = +√(u/v) xx, wasSquare := new(field.Element).SqrtRatio(u, vv) if wasSquare == 0 { return nil, errors.New("edwards25519:...