ParagonIE_Sodium_Core_Ristretto255::ristretto255_p3_tobytes( ParagonIE_Sodium_Core_Curve25519_Ge_P3 $h ): string

196    public static function ristretto255_p3_tobytes(ParagonIE_Sodium_Core_Curve25519_Ge_P3 $h)197    {198        $sqrtm1 = ParagonIE_Sodium_Core_Curve25519_Fe::fromArray(self::$sqrtm1);199        $invsqrtamd = ParagonIE_Sodium_Core_Curve25519_Fe::fromArray(self::$invsqrtamd);200 201        $u1 = self::fe_add($h->Z, $h->Y); /* u1 = Z+Y */202        $zmy = self::fe_sub($h->Z, $h->Y); /* zmy = Z-Y */203        $u1 = self::fe_mul($u1, $zmy); /* u1 = (Z+Y)*(Z-Y) */204        $u2 = self::fe_mul($h->X, $h->Y); /* u2 = X*Y */205 206        $u1_u2u2 = self::fe_mul(self::fe_sq($u2), $u1); /* u1_u2u2 = u1*u2^2 */207        $one = self::fe_1();208 209        // fe25519_1(one);210        // (void) ristretto255_sqrt_ratio_m1(inv_sqrt, one, u1_u2u2);211        $result = self::ristretto255_sqrt_ratio_m1($one, $u1_u2u2);212        $inv_sqrt = $result['x'];213 214        $den1 = self::fe_mul($inv_sqrt, $u1); /* den1 = inv_sqrt*u1 */215        $den2 = self::fe_mul($inv_sqrt, $u2); /* den2 = inv_sqrt*u2 */216        $z_inv = self::fe_mul($h->T, self::fe_mul($den1, $den2)); /* z_inv = den1*den2*T */217 218        $ix = self::fe_mul($h->X, $sqrtm1); /* ix = X*sqrt(-1) */219        $iy = self::fe_mul($h->Y, $sqrtm1); /* iy = Y*sqrt(-1) */220        $eden = self::fe_mul($den1, $invsqrtamd);221 222        $t_z_inv =  self::fe_mul($h->T, $z_inv); /* t_z_inv = T*z_inv */223        $rotate = self::fe_isnegative($t_z_inv);224 225        $x_ = self::fe_copy($h->X);226        $y_ = self::fe_copy($h->Y);227        $den_inv = self::fe_copy($den2);228 229        $x_ = self::fe_cmov($x_, $iy, $rotate);230        $y_ = self::fe_cmov($y_, $ix, $rotate);231        $den_inv = self::fe_cmov($den_inv, $eden, $rotate);232 233        $x_z_inv = self::fe_mul($x_, $z_inv);234        $y_ = self::fe_cneg($y_, self::fe_isnegative($x_z_inv));235 236 237        // fe25519_sub(s_, h->Z, y_);238        // fe25519_mul(s_, den_inv, s_);239        // fe25519_abs(s_, s_);240        // fe25519_tobytes(s, s_);241        return self::fe_tobytes(242            self::fe_abs(243                self::fe_mul(244                    $den_inv,245                    self::fe_sub($h->Z, $y_)246                )247            )248        );249    }