PHP MyCrypt Encoding/Decoding doesn't work

Question

i have a little problem: my decryption won't give me the same string i encoded, and i can't find the problem... looked in other posts, but nothing helpful there here are my functions:

public static function encryptData($data){
    if($key = self::getEncryptionKey()){
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $data, MCRYPT_MODE_ECB,$iv));
    } else {
        return false;
    }
}

public static function decryptData($data)
{
    if($key = self::getEncryptionKey()){
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        return mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, base64_decode($data), MCRYPT_MODE_ECB,$iv);
    } else {
        return false;
    }

}

where's the problem? i'm kinda desperate here...

Perhaps you should use mcrypt_decrypt to decrypt data - or is this just a copy&paste-mistake? — Stefan Gehrig
– Stefan Gehrig, Commented Nov 21, 2011 at 16:56
+1 for using mcrypt_decrypt. @AlexK: Have you seen/tried phpseclib.sourceforge.net? — simshaun
– simshaun, Commented Nov 21, 2011 at 16:59
that's a copy/paste mistake... but i just figured out the problem, he didn't like blanks... — AlexK
– AlexK, Commented Nov 21, 2011 at 17:00

rossum · Accepted Answer · 2011-11-21 18:23:30Z

1

To decrypt you need everything exactly the same at both sides. key, mode, IV and padding.

Looking at your code, you appear to be generating a new IV for decryption. Don't. Use the same IV as you used to encrypt.

You, correctly, specify a mode explicitly, but you pick the worst possible mode. Don't use ECB, it leaks information. Use CBC or CTR mode instead.

You don't specify a padding. Far better to specify it explicitly, use PKCS7 with Rijndael.

If none of that helps, then check your key, byte by byte, to make sure it is the same for both encryption and decryption.

answered Nov 21, 2011 at 18:23

rossum

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2 Comments

DarkSquirrel42 Over a year ago

you are right, ECB should be avoided, but whatever he supplies as IV shouldn't make any difference here

Maarten Bodewes Over a year ago

That's the second time in so many days that I've seen an issue with PHP, ECB & IV vector involved. Are we sure that IV is not included in the calculation of the first block? Can somebody check?

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