decrypt a as3crypto encrypted text in PHP

Question

i tried to encrypt a text in as3crypto via the demo app.

now i am trying to decrypt the crypted text via php but it seems that the text is not properly decrypted. has anyone know how to properly decrypt it via PHP? or am I doing it wrong? please enlighten me...

here's the scenario:

1. encrypt this in http://crypto.hurlant.com/demo/:

   encryption: AES

   mode: CBC

   padding: none

   key: 11918f8bcd112e92744125008722050c

   text: Lorem ipsum dolor sit amet, consectetur adipiscing elit. In ut massa nec purus laoreet posuere quis vitae tortor.

   initialize vector: leave it blank

2. press encrypt. select base64 and copy the cipher text.

3. make a php script that has these codes and run it:

   $cipher = MCRYPT_RIJNDAEL_128;

   $mode = MCRYPT_MODE_CBC;

   $key = "11918f8bcd112e92744125008722050c";

   $cipher = "PLACE CIPHER TEXT HERE...";

   $data = base64_decode($cipher);

   echo mcrypt_decrypt($cipher, $key, $data, $mode);

Answer 1

the issue probably lies in your key. While you can feed a hex string to as3crypto and it will know what do to with it, mcrypt_decrypt will interpret each character as it's underlying ASCII value (like a = 97) instead of it's hexadecimal value (a = 10). Use the hex2bin method to convert the hex string into a byte string, and your decryption should probably work fine.

also, an issue may rest with different ideas of a default IV (initialization vector) between as3crypto and php. Since you are using CBC mode, you should be specifying an IV, just as a good security practice. also be aware of the potential pitfalls similar to those with your key, of specifying a hex string in as3 and needing to convert it in php.