Question

I’m trying to decrypt it in Xcode with AES-Crypt-Objc. I’have tried really everything..different libariers and so on..

..anyhting goes wrong, but I don’t know what pls. help…

UPDATE (another opinion)
Now i try this:

function mc_encrypt($encrypt, $key = "12345678901234567890123456789012") 
{
    $encrypt = "Affe";
    $iv2 = ''; 
    for($i=0;$i<16;$i++){ $iv2 .= "\0";  }

    $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, ($encrypt), MCRYPT_MODE_CBC,$iv2);
    $encode= base64_encode($ciphertext);

    return $encode;
}

in Obj-C I use also the same framework (still IV is now nil)

…still nothing works…

AND some Objc-C Code:
note: request responseString is the string comes from above.

NSString *key = @"12345678901234561234567890123456";
NSLog(@"decrypted: %@",[AESCrypt decrypt:[request responseString] password:key]);

output is sometimes nothing, sometimes null.

Answer 1

For most systems, encryption should be non-deterministic — encrypting the same plaintext twice should almost never give the same ciphertext. Why? Let’s say you send “attack at dawn” at midnight on day 0 to your accomplice, the attack fails (but you get away unharmed), and at midnight on day 1 you send “attack at dawn” again…

Apart from that, let me count the ways:

• You haven’t shown any ObjC code, so it’s difficult to tell what’s going wrong there.
• Your PHP code uses, oddly, a 26-character “key”. It should be 16 bytes for AES-128. I don’t know how PHP’s mcrypt handles overlong keys; the ObjC code adds zero-padding in FixKeyLengths().
• Both the PHP (as you’ve shown it) and ObjC code (by default) use fixed IVs. Very bad.
  • They use different IVs, which is probably why you get different answers.

FWIW, I’ve seen that that (or similar) ObjC code all over the place. I can’t un-recommend it enough; it really isn’t suitable for general usage.

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