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   1  <?php
   2  
   3  if (class_exists('ParagonIE_Sodium_Core_ChaCha20_IetfCtx', false)) {
   4      return;
   5  }
   6  
   7  /**
   8   * Class ParagonIE_Sodium_Core_ChaCha20_IetfCtx
   9   */
  10  class ParagonIE_Sodium_Core_ChaCha20_IetfCtx extends ParagonIE_Sodium_Core_ChaCha20_Ctx
  11  {
  12      /**
  13       * ParagonIE_Sodium_Core_ChaCha20_IetfCtx constructor.
  14       *
  15       * @internal You should not use this directly from another application
  16       *
  17       * @param string $key     ChaCha20 key.
  18       * @param string $iv      Initialization Vector (a.k.a. nonce).
  19       * @param string $counter The initial counter value.
  20       *                        Defaults to 4 0x00 bytes.
  21       * @throws InvalidArgumentException
  22       * @throws TypeError
  23       */
  24      public function __construct($key = '', $iv = '', $counter = '')
  25      {
  26          if (self::strlen($iv) !== 12) {
  27              throw new InvalidArgumentException('ChaCha20 expects a 96-bit nonce in IETF mode.');
  28          }
  29          parent::__construct($key, self::substr($iv, 0, 8), $counter);
  30  
  31          if (!empty($counter)) {
  32              $this->container[12] = self::load_4(self::substr($counter, 0, 4));
  33          }
  34          $this->container[13] = self::load_4(self::substr($iv, 0, 4));
  35          $this->container[14] = self::load_4(self::substr($iv, 4, 4));
  36          $this->container[15] = self::load_4(self::substr($iv, 8, 4));
  37      }
  38  }