This is a wrapper around RNCryptor for Titanium. It assists in correctly encrypting and decrypting data with AES. See the RNCryptor docs for full details.
There are several important caveats:
I don't actively support this wrapper anymore. Anyone interested in doing so, please contact me.
This wrapper requires CommonCryptor, which is specific to iOS. That means that it only works on iOS. This is not a cross-platform solution.
Given the above, I don't especially recommend this module. I don't really recommend Titanium at all, and particularlly don't recommend Titanium as an iOS-only development platform. But if using CommonCrypto is important to you, then this is an option. RNCryptor also optionally interoperates with OpenSSL, which can be useful (though OpenSSL is not a very secure format and I don't recommend it if you can avoid it).