<?php

if (class_exists('ParagonIE_Sodium_Core_XSalsa20', false)) {

    return;

}

/**

 * Class ParagonIE_Sodium_Core_XSalsa20

 */

abstract class ParagonIE_Sodium_Core_XSalsa20 extends ParagonIE_Sodium_Core_HSalsa20

{

    /**

     * Expand a key and nonce into an xsalsa20 keystream.

     *

     * @internal You should not use this directly from another application

     *

     * @param int $len

     * @param string $nonce

     * @param string $key

     * @return string

     * @throws SodiumException

     * @throws TypeError

     */

    public static function xsalsa20($len, $nonce, $key)

    {

        $ret = self::salsa20(

            $len,

            self::substr($nonce, 16, 8),

            self::hsalsa20($nonce, $key)

        );

        return $ret;

    }

    /**

     * Encrypt a string with XSalsa20. Doesn't provide integrity.

     *

     * @internal You should not use this directly from another application

     *

     * @param string $message

     * @param string $nonce

     * @param string $key

     * @return string

     * @throws SodiumException

     * @throws TypeError

     */

    public static function xsalsa20_xor($message, $nonce, $key)

    {

        return self::xorStrings(

            $message,

            self::xsalsa20(

                self::strlen($message),

                $nonce,

                $key

            )

        );

    }

}