AES256 decryption issue in Objective-c

Question

I am trying to use the following snippet to decrypt file, which was encrypted with 32 byte key. So when I am trying to encrypt file data, everything is going ok. But when I am t

Answer 1

This code has significant security issues. It incorrectly constructs the AES key, drastically reducing the keyspace and has no IV, creating problems for the first block. I strongly recommend against this code.

I'm most of the way through developing a replacement for this commonly-used snippet. See https://github.com/rnapier/RNCryptor. If it doesn't work for you out of the box, let me know. I'm trying to make it easy enough to use for all the common cases that people will stop using AES256EncryptWithKey.

For a much longer discussion about the problems with this code, see Properly encrypting with AES with CommonCrypto. I love that someone wrapped up AES encryption into an easy to use category. I just wish that it hadn't had so many security issues.

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EDIT: Coming back to your actual question, did you use AES256EncryptWithKey to encrypt this data? If not, then the specific format is likely radically different. Almost every AES encryption implementation uses a different approach in generating its input parameters and then generating its output (most don't document this well, either). You have to match the parameters and format. For example, you can't use AES256EncryptWithKey to decrypt something generated with openssl enc.