ParagonIE_Sodium_Core_Curve25519::ge_scalarmult( string $a, ParagonIE_Sodium_Core_Curve25519_Ge_P3 $p ): ParagonIE_Sodium_Core_Curve25519_Ge_P3

1879    public static function ge_scalarmult($a, $p)1880    {1881        $e = array_fill(0, 64, 0);1882 1883        /** @var ParagonIE_Sodium_Core_Curve25519_Ge_Cached[] $pi */1884        $pi = array();1885 1886        //        ge25519_p3_to_cached(&pi[1 - 1], p);   /* p */1887        $pi[0] = self::ge_p3_to_cached($p);1888 1889        //        ge25519_p3_dbl(&t2, p);1890        //        ge25519_p1p1_to_p3(&p2, &t2);1891        //        ge25519_p3_to_cached(&pi[2 - 1], &p2); /* 2p = 2*p */1892        $t2 = self::ge_p3_dbl($p);1893        $p2 = self::ge_p1p1_to_p3($t2);1894        $pi[1] = self::ge_p3_to_cached($p2);1895 1896        //        ge25519_add_cached(&t3, p, &pi[2 - 1]);1897        //        ge25519_p1p1_to_p3(&p3, &t3);1898        //        ge25519_p3_to_cached(&pi[3 - 1], &p3); /* 3p = 2p+p */1899        $t3 = self::ge_add($p, $pi[1]);1900        $p3 = self::ge_p1p1_to_p3($t3);1901        $pi[2] = self::ge_p3_to_cached($p3);1902 1903        //        ge25519_p3_dbl(&t4, &p2);1904        //        ge25519_p1p1_to_p3(&p4, &t4);1905        //        ge25519_p3_to_cached(&pi[4 - 1], &p4); /* 4p = 2*2p */1906        $t4 = self::ge_p3_dbl($p2);1907        $p4 = self::ge_p1p1_to_p3($t4);1908        $pi[3] = self::ge_p3_to_cached($p4);1909 1910        //        ge25519_add_cached(&t5, p, &pi[4 - 1]);1911        //        ge25519_p1p1_to_p3(&p5, &t5);1912        //        ge25519_p3_to_cached(&pi[5 - 1], &p5); /* 5p = 4p+p */1913        $t5 = self::ge_add($p, $pi[3]);1914        $p5 = self::ge_p1p1_to_p3($t5);1915        $pi[4] = self::ge_p3_to_cached($p5);1916 1917        //        ge25519_p3_dbl(&t6, &p3);1918        //        ge25519_p1p1_to_p3(&p6, &t6);1919        //        ge25519_p3_to_cached(&pi[6 - 1], &p6); /* 6p = 2*3p */1920        $t6 = self::ge_p3_dbl($p3);1921        $p6 = self::ge_p1p1_to_p3($t6);1922        $pi[5] = self::ge_p3_to_cached($p6);1923 1924        //        ge25519_add_cached(&t7, p, &pi[6 - 1]);1925        //        ge25519_p1p1_to_p3(&p7, &t7);1926        //        ge25519_p3_to_cached(&pi[7 - 1], &p7); /* 7p = 6p+p */1927        $t7 = self::ge_add($p, $pi[5]);1928        $p7 = self::ge_p1p1_to_p3($t7);1929        $pi[6] = self::ge_p3_to_cached($p7);1930 1931        //        ge25519_p3_dbl(&t8, &p4);1932        //        ge25519_p1p1_to_p3(&p8, &t8);1933        //        ge25519_p3_to_cached(&pi[8 - 1], &p8); /* 8p = 2*4p */1934        $t8 = self::ge_p3_dbl($p4);1935        $p8 = self::ge_p1p1_to_p3($t8);1936        $pi[7] = self::ge_p3_to_cached($p8);1937 1938 1939        //        for (i = 0; i < 32; ++i) {1940        //            e[2 * i + 0] = (a[i] >> 0) & 15;1941        //            e[2 * i + 1] = (a[i] >> 4) & 15;1942        //        }1943        for ($i = 0; $i < 32; ++$i) {1944            $e[($i << 1)    ] =  self::chrToInt($a[$i]) & 15;1945            $e[($i << 1) + 1] = (self::chrToInt($a[$i]) >> 4) & 15;1946        }1947        //        /* each e[i] is between 0 and 15 */1948        //        /* e[63] is between 0 and 7 */1949 1950        //        carry = 0;1951        //        for (i = 0; i < 63; ++i) {1952        //            e[i] += carry;1953        //            carry = e[i] + 8;1954        //            carry >>= 4;1955        //            e[i] -= carry * ((signed char) 1 << 4);1956        //        }1957        $carry = 0;1958        for ($i = 0; $i < 63; ++$i) {