phpBB::_hash_crypt_private( $password,  $setting,  $itoa64 )

	private function _hash_crypt_private( $password, $setting, &$itoa64 ) {
		$output = '*';

		// Check for correct hash
		if ( substr( $setting, 0, 3 ) != '$H$' ) {
			return $output;
		}

		$count_log2 = strpos( $itoa64, $setting[3] );

		if ( $count_log2 < 7 || $count_log2 > 30 ) {
			return $output;
		}

		$count = 1 << $count_log2;
		$salt  = substr( $setting, 4, 8 );

		if ( strlen( $salt ) != 8 ) {
			return $output;
		}

		/**
		 * We're kind of forced to use MD5 here since it's the only
		 * cryptographic primitive available in all versions of PHP
		 * currently in use.  To implement our own low-level crypto
		 * in PHP would result in much worse performance and
		 * consequently in lower iteration counts and hashes that are
		 * quicker to crack (by non-PHP code).
		 */
		if ( floatval( phpversion() ) >= 5 ) {
			$hash = md5( $salt . $password, true );
			do
			{
				$hash = md5( $hash . $password, true );
			}
			while ( --$count );
		} else {
			$hash = pack( 'H*', md5( $salt . $password ) );
			do {
				$hash = pack( 'H*', md5( $hash . $password ) );
			}
			while ( --$count );
		}

		$output = substr($setting, 0, 12);
		$output .= $this->_hash_encode64($hash, 16, $itoa64);

		return $output;
	}