I encrypt messages for a another, goofier purpose. One of the people I am encrypting from is a compsci professor.

I use a Vigenere cipher, which should beat everything short of the Secret Werewolf Police, and possibly them, too. (It is, however, more crackable than a proper salted, hashed output.)

In a Vigenere, the letters in your input are moved by the numerical equivalent of the key, and the key repeats. Example:

Secret Statement/lie: Cats are nice. Key: ABC

New, coded statement: dcwt (down 1, 2, 3, 1) cuf ildg. Now, I recommend using long keys and spacing the output in five letter blocks to prevent easier soliving.

You can do this online:

http://sharkysoft.com/vigenere/

This will transmute "It seems unlikely the werewolf police will catch you," with the key "The movie ends the same way for all of us JRM." to:

Cbxrt ibzsz mdytd minyzw wxqdt cjeph bfqhr leuqh oxvbg tn.

(Letter grouping by me.)

Again Vigenere's are potentially crackable, but they are very hard. It's easier for the werewolf police to just come and eat anyone who puts up hashed or Vigenere ciphered predictions.