1<?php
  2
  3if (class_exists('ParagonIE_Sodium_Core32_XSalsa20', false)) {
  4    return;
  5}
  6
  7/**
  8 * Class ParagonIE_Sodium_Core32_XSalsa20
  9 */
 10abstract class ParagonIE_Sodium_Core32_XSalsa20 extends ParagonIE_Sodium_Core32_HSalsa20
 11{
 12    /**
 13     * Expand a key and nonce into an xsalsa20 keystream.
 14     *
 15     * @internal You should not use this directly from another application
 16     *
 17     * @param int $len
 18     * @param string $nonce
 19     * @param string $key
 20     * @return string
 21     * @throws SodiumException
 22     * @throws TypeError
 23     */
 24    public static function xsalsa20($len, $nonce, $key)
 25    {
 26        $ret = self::salsa20(
 27            $len,
 28            self::substr($nonce, 16, 8),
 29            self::hsalsa20($nonce, $key)
 30        );
 31        return $ret;
 32    }
 33
 34    /**
 35     * Encrypt a string with XSalsa20. Doesn't provide integrity.
 36     *
 37     * @internal You should not use this directly from another application
 38     *
 39     * @param string $message
 40     * @param string $nonce
 41     * @param string $key
 42     * @return string
 43     * @throws SodiumException
 44     * @throws TypeError
 45     */
 46    public static function xsalsa20_xor($message, $nonce, $key)
 47    {
 48        return self::xorStrings(
 49            $message,
 50            self::xsalsa20(
 51                self::strlen($message),
 52                $nonce,
 53                $key
 54            )
 55        );
 56    }
 57}
 58