Difference in PHP encryption from iOS and .NET

Question

I have an issue when communicating encrypted between iOS and PHP. I have an app that encrypts a string and sends it to a PHP server that decrypts it. That part works just fi

Answer 1

Most likely it's a padding issue... Please see here or here for more information.

EDIT after OP comment:

PHP has no built-in support for other padding modes than the NULL-padding. At least .Net allows you to specify NULL-padding (I think), the other option would be to implement PKCS#7-padding in PHP which is not that difficult to do.

Pad the input with a padding string of between 1 and 8 bytes to make the total length an exact multiple of 8 bytes. The value of each byte of the padding string is set to the number of bytes added - i.e. 8 bytes of value 0x08, 7 bytes of value 0x07, ..., 2 bytes of 0x02, or one byte of value 0x01.

$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
$padding   = $blockSize - (strlen($data) % $blockSize);
$data      .= str_repeat(chr($padding), $padding);