ParagonIE_Sodium_Core_Ed25519

13abstract class ParagonIE_Sodium_Core_Ed25519 extends ParagonIE_Sodium_Core_Curve2551914{15    const KEYPAIR_BYTES = 96;16    const SEED_BYTES = 32;17    const SCALAR_BYTES = 32;18 19    /**20     * @internal You should not use this directly from another application21     *22     * @return string (96 bytes)23     * @throws Exception24     * @throws SodiumException25     * @throws TypeError26     */27    public static function keypair()28    {29        $seed = random_bytes(self::SEED_BYTES);30        $pk = '';31        $sk = '';32        self::seed_keypair($pk, $sk, $seed);33        return $sk . $pk;34    }35 36    /**37     * @internal You should not use this directly from another application38     *39     * @param string $pk40     * @param string $sk41     * @param string $seed42     * @return string43     * @throws SodiumException44     * @throws TypeError45     */46    public static function seed_keypair(&$pk, &$sk, $seed)47    {48        if (self::strlen($seed) !== self::SEED_BYTES) {49            throw new RangeException('crypto_sign keypair seed must be 32 bytes long');50        }51 52        /** @var string $pk */53        $pk = self::publickey_from_secretkey($seed);54        $sk = $seed . $pk;55        return $sk;56    }57 58    /**59     * @internal You should not use this directly from another application60     *61     * @param string $keypair62     * @return string63     * @throws TypeError64     */65    public static function secretkey($keypair)66    {67        if (self::strlen($keypair) !== self::KEYPAIR_BYTES) {68            throw new RangeException('crypto_sign keypair must be 96 bytes long');69        }70        return self::substr($keypair, 0, 64);71    }72 73    /**74     * @internal You should not use this directly from another application75     *76     * @param string $keypair77     * @return string78     * @throws TypeError79     */80    public static function publickey($keypair)81    {82        if (self::strlen($keypair) !== self::KEYPAIR_BYTES) {83            throw new RangeException('crypto_sign keypair must be 96 bytes long');84        }85        return self::substr($keypair, 64, 32);86    }87 88    /**89     * @internal You should not use this directly from another application90     *91     * @param string $sk92     * @return string