Caesar Cypher

The Caeser Cypher is a substitution cypher and one of the oldest ways to crypt a message: it was used during Roman Empire to crypt, military information.

A substitution cypher is cryptology technique in which each letter of a message is replaced by another one: it is therefore a symmetric cypher (the same algorithm is used to cypher and to decypher a message).

In the Caeser Cypher, the key used to cypher a message is a number which is the shift.

Here's an example:
message: HELLO WORLD
shift: 10
cyphered message: ROVVY GYBVN

This is a very easy algorithm and therefore not secure at all! If you don't know the key, you can simply try every shift, i.e. 25 (and not 26 because then you fall on the original cyphered message), and see which message seems the most coherent.

Now, here's a little treat, a nice screenshot of GU-Cypher. As you see, since I'm under Linux, the graphical interface is in GTK. Under Windows however, it will use the normal Windows graphical environment. ;)



P.S.: part of the treat is the website you see in, the background of the screenshot, that's version 4 of the website, online soon if I get my act together!