I'd like to use AES in a haskell program that I'm writing. I've come across three libraries in hackage that do AES: the library named AES, the Crypto library, and the SimpleAES library. The library named AES says in its documentation for the "crypt" function that it is not thread-safe. What exactly does this mean in haskell? Does it mean that if you have separate AESCtx instances in different forkIO "threads", that things will break? Or does it just mean that using the same AESCtx in multiple forkIO threads is a bad idea? I'm asking about that one comment because it looks like SimpleAES is probably a wrapper around AES, and the Crypto library also says it uses a library named AES, although one by an author not listed in the hackage AES library entry. Can anybody shed some light on the state of AES encryption in haskell? What is the preferred library, especially for us in a program that has many forkIO'd "threads"?