ParagonIE_Sodium_Core32_Curve25519::ge_frombytes_negate_vartime() public WP 1.0

{} It's a method of the class: ParagonIE_Sodium_Core32_Curve25519{}

No Hooks.

Return

ParagonIE_Sodium_Core32_Curve25519_Ge_P3.

Usage

$result = ParagonIE_Sodium_Core32_Curve25519::ge_frombytes_negate_vartime( $s );

$s(string) (required)

-

Code of ParagonIE_Sodium_Core32_Curve25519::ge_frombytes_negate_vartime() ParagonIE Sodium Core32 Curve25519::ge frombytes negate vartime ^{WP 5.8.2}

public static function ge_frombytes_negate_vartime($s)
{
    static $d = null;
    if (!$d) {
        /** @var ParagonIE_Sodium_Core32_Curve25519_Fe $d */
        $d = ParagonIE_Sodium_Core32_Curve25519_Fe::fromArray(
            array(
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[0]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[1]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[2]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[3]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[4]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[5]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[6]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[7]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[8]),
                ParagonIE_Sodium_Core32_Int32::fromInt(self::$d[9])
            )
        );
    }

    # fe_frombytes(h->Y,s);
    # fe_1(h->Z);
    $h = new ParagonIE_Sodium_Core32_Curve25519_Ge_P3(
        self::fe_0(),
        self::fe_frombytes($s),
        self::fe_1()
    );

    # fe_sq(u,h->Y);
    # fe_mul(v,u,d);
    # fe_sub(u,u,h->Z);       /* u = y^2-1 */
    # fe_add(v,v,h->Z);       /* v = dy^2+1 */
    $u = self::fe_sq($h->Y);
    /** @var ParagonIE_Sodium_Core32_Curve25519_Fe $d */
    $v = self::fe_mul($u, $d);
    $u = self::fe_sub($u, $h->Z); /* u =  y^2 - 1 */
    $v = self::fe_add($v, $h->Z); /* v = dy^2 + 1 */

    # fe_sq(v3,v);
    # fe_mul(v3,v3,v);        /* v3 = v^3 */
    # fe_sq(h->X,v3);
    # fe_mul(h->X,h->X,v);
    # fe_mul(h->X,h->X,u);    /* x = uv^7 */
    $v3 = self::fe_sq($v);
    $v3 = self::fe_mul($v3, $v); /* v3 = v^3 */
    $h->X = self::fe_sq($v3);
    $h->X = self::fe_mul($h->X, $v);
    $h->X = self::fe_mul($h->X, $u); /* x = uv^7 */

    # fe_pow22523(h->X,h->X); /* x = (uv^7)^((q-5)/8) */
    # fe_mul(h->X,h->X,v3);
    # fe_mul(h->X,h->X,u);    /* x = uv^3(uv^7)^((q-5)/8) */
    $h->X = self::fe_pow22523($h->X); /* x = (uv^7)^((q-5)/8) */
    $h->X = self::fe_mul($h->X, $v3);
    $h->X = self::fe_mul($h->X, $u); /* x = uv^3(uv^7)^((q-5)/8) */

    # fe_sq(vxx,h->X);
    # fe_mul(vxx,vxx,v);
    # fe_sub(check,vxx,u);    /* vx^2-u */
    $vxx = self::fe_sq($h->X);
    $vxx = self::fe_mul($vxx, $v);
    $check = self::fe_sub($vxx, $u); /* vx^2 - u */

    # if (fe_isnonzero(check)) {
    #     fe_add(check,vxx,u);  /* vx^2+u */
    #     if (fe_isnonzero(check)) {
    #         return -1;
    #     }
    #     fe_mul(h->X,h->X,sqrtm1);
    # }
    if (self::fe_isnonzero($check)) {
        $check = self::fe_add($vxx, $u); /* vx^2 + u */
        if (self::fe_isnonzero($check)) {
            throw new RangeException('Internal check failed.');
        }
        $h->X = self::fe_mul(
            $h->X,
            ParagonIE_Sodium_Core32_Curve25519_Fe::fromIntArray(self::$sqrtm1)
        );
    }

    # if (fe_isnegative(h->X) == (s[31] >> 7)) {
    #     fe_neg(h->X,h->X);
    # }
    $i = self::chrToInt($s[31]);
    if (self::fe_isnegative($h->X) === ($i >> 7)) {
        $h->X = self::fe_neg($h->X);
    }

    # fe_mul(h->T,h->X,h->Y);
    $h->T = self::fe_mul($h->X, $h->Y);
    return $h;
}