/**
* Compute the shared secret key based on the public key received from the
* the second party to this transaction. This should agree to the secret
* key the second party computes on our own public key.
* Once in agreement, the key is known to only to both parties.
* By default, the function expects the public key to be in binary form
* which is the typical format when being transmitted.
*
* If you need the binary form of the shared secret key, call
* getSharedSecretKey() with the optional parameter for Binary output.
*
* @param string $publicKey
* @param string $type
* @param string $output
* @throws Zend_Crypt_DiffieHellman_Exception
* @return mixed
*/
public function computeSecretKey($publicKey, $type = self::NUMBER, $output = self::NUMBER)
{
if ($type == self::BINARY) {
$publicKey = $this->_math->fromBinary($publicKey);
}
if (!preg_match("/^\\d+\$/", $publicKey)) {
throw new Zend_Crypt_DiffieHellman_Exception('invalid parameter; not a positive natural number');
}
if (function_exists('openssl_dh_compute_key') && self::$useOpenssl !== false) {
$this->_secretKey = openssl_dh_compute_key($publicKey, $this->getPublicKey());
} else {
$this->_secretKey = $this->_math->powmod($publicKey, $this->getPrivateKey(), $this->getPrime());
}
return $this->getSharedSecretKey($output);
}
