PHP mcrypt and SQL Where for Encrypted Info? - php

Question

I Have a function where text is encrypted and decrypted. On every refresh the encryption is always different and the decrypted is always the same as the original string. I update to a sql database the encryption. I Can't Use a simple "SELECT * FROM mytable WHERE MyField = 'Myencryption';" because the 'Myencryption' will be different each time. How can I search in SQL an Mycrypt Encryption? Any Suggestions?
My Code is Below: ( I have a PDO SQL Class )
// Encrypt Function
private function encrypt($encrypt, $key){
$encrypt = serialize($encrypt);
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC), MCRYPT_DEV_URANDOM);
$mac = hash_hmac('sha256', $encrypt, substr(bin2hex($key), -32));
$passcrypt = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $encrypt.$mac, MCRYPT_MODE_CBC, $iv);
$encoded = base64_encode($passcrypt).'|'.base64_encode($iv);
return $encoded;
}
// Decrypt Function
private function decrypt($decrypt, $key){
$decrypt = explode('|', $decrypt.'|');
$decoded = base64_decode($decrypt[0]);
$iv = base64_decode($decrypt[1]);
if(strlen($iv)!==mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC)){ return false; }
$decrypted = trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $decoded, MCRYPT_MODE_CBC, $iv));
$mac = substr($decrypted, -64);
$decrypted = substr($decrypted, 0, -64);
$calcmac = hash_hmac('sha256', $decrypted, substr(bin2hex($key), -32));
if($calcmac!==$mac){ return false; }
$decrypted = unserialize($decrypted);
return $decrypted;
} // End Decrypt
$this->db->query("SELECT * FROM `$this->main_db`.`$this->apps_tbl` WHERE `2` = ':db_name'");
$this->db->bind(':db_name', $app_id);
$row = $this->db->single();

Answer 1

SELECT * FROM mytable WHERE 'text' = AES_DECRYPT(MyField, 'Your 256 key');
But if you have many rows in table or weak server, this way may be quite slow.