Selecting Encrypted Data from MySQL - php

Question

I am storing some encrypted information in a MySQL database, but I can't get it back out for some reason. I am storing the encrypted data as BINARY(46). Why is my select statement failing?
Here is my SELECT statement:
SELECT max(created) FROM incentive_sales WHERE incentive_sales.accountID = :aid
So shouldn't I encrypt the accountID (:aid) for my select statement?
Here is my encrypt function:
private function _encrypt($decrypted, $password, $salt = '|SgQLL*ea!UMwf^s%'){
// Build a 256-bit $key which is a SHA256 hash of $salt and $password.
$key = hash('SHA256', $salt . $password, true);
// Build $iv and $iv_base64. We use a block size of 128 bits (AES compliant) and CBC mode. (Note: ECB mode is inadequate as IV is not used.)
srand(); $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
if (strlen($iv_base64 = rtrim(base64_encode($iv), '=')) != 22){
return false;
}
// Encrypt $decrypted using $key.
$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $decrypted, MCRYPT_MODE_CBC, $iv));
return $iv_base64.$encrypted;
}
And my decrypt function:
private function _decrypt($encrypted, $password, $salt = '|SgQLL*ea!UMwf^s%'){
// Build a 256-bit $key which is a SHA256 hash of $salt and $password.
$key = hash('SHA256', $salt . $password, true);
// Retrieve $iv which is the first 22 characters plus ==, base64_decoded.
$iv = base64_decode(substr($encrypted, 0, 22) . '==');
// Remove $iv from $encrypted.
$encrypted = substr($encrypted, 22);
// Decrypt the data.
$decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, base64_decode($encrypted), MCRYPT_MODE_CBC, $iv)
return $decrypted;
}

Answer 1

The correct answer is, "As far as I know, you cannot use encrypted data as a selection in the where clause because it will always be different."
To circumvent this (because I do want to be able to select based on the encrypted data), I also store a hashed/salted value of the encrypted data which I then use in my select statement.