Thanks for your help, not sure why I'd put the key in the State. The execState and pointfree-ing made it a lot nicer. You're right on the foldr/flip, but I wasn't zeroing the i & j parts of the PRGA, so now I have: ksa' :: Key -> PRGA ksa' key = (prga,0,0) -- have to zero where (prga,_,_) = foldr (execState . ksaStep' key) (permId,0,0) [255,254..0] I need the [255,254..0] since it has to count up, and the "where" to set the zeros. I'm not sure if those are worth fixing, or what can be done to make either of those any better. Any suggestions would be appreciated. As for running, I was just running "pwCrypt "key" "plaintext"" in ghci and checking against the expected keystream/ciphertext.
And man I just want to say how jealous I am. I wish I could go to a ny haskell group :(.
There's a meeting this week! Edward Kmett and his lens library. Last month's had a good crowd, very friendly.