There are tons of functions along those lines. Your query is not very specific. What kind of algorithm do you want, public-key or secret-key? What size key? Blocksize? whatever.
You've just defined an abstraction that includes every single encryption function known to man....
-derek
It should be a secret key algorithm, and be able to hanlde blocks of at least 256 characters in length. Keysize isn't as important as the type of encryption being used. Something that is reasonably secure such as IDEA or DES is preferable to a function that just XORs everything. I'm sure if I was a more patient person I could download a few megs of source from the net and pore through it to find what I'm looking for. I was hoping that someone on this list could be of assistance and save me the trouble. Thanks.