krypton2
create a file that contains all the letters in the alphabet, and run the encrypt binary on the file. Now you have a one-to-one map of all the letters and their correspondants. Using this info you can easily decode the string:
abcdefghijklmnopqrstuvwxyz
MNOPQRSTUVWXYZABCDEFGHIJKL
OMQEMDUEQMEK
caeseriseasy (CAESARISEASY)