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<?php
/**
* OpenSSL Modular Exponentiation Engine
*
* PHP version 5 and 7
*
* @author Jim Wigginton <[email protected]>
* @copyright 2017 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://pear.php.net/package/Math_BigInteger
*/
namespace phpseclib3\Math\BigInteger\Engines;
use phpseclib3\Crypt\RSA\Formats\Keys\PKCS8;
use phpseclib3\Math\BigInteger;
/**
* OpenSSL Modular Exponentiation Engine
*
* @author Jim Wigginton <[email protected]>
*/
abstract class OpenSSL
{
/**
* Test for engine validity
*
* @return bool
*/
public static function isValidEngine()
{
return extension_loaded('openssl') && static::class != __CLASS__;
}
/**
* Performs modular exponentiation.
*
* @param Engine $x
* @param Engine $e
* @param Engine $n
* @return Engine
*/
public static function powModHelper(Engine $x, Engine $e, Engine $n)
{
if ($n->getLengthInBytes() < 31 || $n->getLengthInBytes() > 16384) {
throw new \OutOfRangeException('Only modulo between 31 and 16384 bits are accepted');
}
$key = PKCS8::savePublicKey(
new BigInteger($n),
new BigInteger($e)
);
$plaintext = str_pad($x->toBytes(), $n->getLengthInBytes(), "\0", STR_PAD_LEFT);
// this is easily prone to failure. if the modulo is a multiple of 2 or 3 or whatever it
// won't work and you'll get a "failure: error:0906D06C:PEM routines:PEM_read_bio:no start line"
// error. i suppose, for even numbers, we could do what PHP\Montgomery.php does, but then what
// about odd numbers divisible by 3, by 5, etc?
if (!openssl_public_encrypt($plaintext, $result, $key, OPENSSL_NO_PADDING)) {
throw new \UnexpectedValueException(openssl_error_string());
}
$class = get_class($x);
return new $class($result, 256);
}
}
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