MCrypt rijndael-256 to OpenSSL aes-256-ecb conversion

Question

Since Mcrypt is deprecated, I want to use OpenSSL instead in my code since we already using php 7.2.4 in our server.

I have used following code for Encryption/Decryption.

//ENCRYPTION

function encrypt($text, $salt='') {
    if ($text == "") {
        return "";
    }

    if ($salt == "") {
        $salt = 'DiAo74dOO09T48YESmuvbS0T';
    }

    return trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $salt, $text, MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND))));
}

//DECRYPTION

function decrypt($text, $salt = '') {
    if ($text == "") {
        return "";
    }

    if ($salt == "") {
        $salt = 'DiAo74dOO09T48YESmuvbS0T';
    }

    return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $salt, base64_decode($text), MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND)));
}

AFdT9sa81krHkp/GoYCSwh7/lZn/gLZLHJSldi5/QCU= this string I had encrypted using the above encryption function, but I want it to decrypt it using OPENSSL. I used the following code to decrypt it:

$string = 'AFdT9sa81krHkp/GoYCSwh7/lZn/gLZLHJSldi5/QCU=';   
$output = false;
$secret_key = 'DiAo74dOO09T48YESmuvbS0T';   
$secret_iv1 = openssl_random_pseudo_bytes(openssl_cipher_iv_length('AES-256-ECB'));
$secret_iv = bin2hex($secret_iv1);
$key = hash('sha256', $secret_key);    
$iv = substr(hash('sha256', $secret_iv), 0, 16);

$output = base64_encode(openssl_encrypt($string, 'aes-256-ecb', $key, OPENSSL_RAW_DATA));

I want decrypted output as: durhs-14767-w0163j1-89047 Thanks in advance for your reply.

Answer 1

Saddly, you are on the wrong way.

Refer to :

http://php.net/manual/en/function.mcrypt-encrypt.php#117667

MCRYPT_RIJNDAEL_256 is not AES-256, it's a different variant of the Rijndael block cipher.

https://en.wikipedia.org/wiki/Advanced_Encryption_Standard

AES is a variant of Rijndael which has a fixed block size of 128 bits, and a key size of 128, 192, or 256 bits. By contrast, the Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, with a minimum of 128 and a maximum of 256 bits.

So you can not use OpenSSL's AES-256 to decrypt the MCrypt's output.

Some possible methods:

1. Keep using mcrypt by PECL's mcrypt extension (luckily, it is still there), until you can replace the legacy data totally.

2. Rewrite a correct RIJNDAEL-256 cipher in PHP.