/**
* https://tools.ietf.org/html/rfc7518#section-5.2.2.1
* @param string $plain_text
* @param string $key
* @param string $iv
* @param string $aad
* @return \string[]
* @throws InvalidKeyLengthAlgorithmException
*/
public function encrypt($plain_text, $key, $iv, $aad)
{
$key_len = strlen($key);
if ($this->getMinKeyLen() > ByteUtil::bitLength($key_len)) {
throw new InvalidKeyLengthAlgorithmException();
}
$enc_key_len = $key_len / 2;
// ENC_KEY = final ENC_KEY_LEN octets of K
$enc_key = substr($key, $enc_key_len);
$this->aes->setKey($enc_key);
$this->aes->setIV($iv);
$cypher_text = $this->aes->encrypt($plain_text);
$tag = $this->calculateAuthenticationTag($cypher_text, $key, $iv, $aad);
return array($cypher_text, $tag);
}
/**
* @return int
*/
public function getBitLength()
{
return ByteUtil::bitLength(strlen($this->secret));
}