Caesar Cipher Encrypt & Decrypt

About Caesar cipher :

Caesar cipher is a basic letters substitution algorithm. It takes as input a message, and apply to every letter a particular shift. This shift used to be 3, according to history, when it was use by Caesar to encrypt war messages (so for example a would become d, b wille be e, and so on and so forth). Of course you can choose any shift you want. This is basically a modulo 26 addition; Caesar cipher, as Polybius Square cipher, is a monoalphabetical cipher. Like the others of this kind, the problem of this cipher is its really poor security. To break it, you can, like I do here, apply every shift to the ciphertext, and see if there's one that makes sense. The other way to break it is by looking to letters frequency. For example we know that in english the e is very frequent, then the t, then a, etc. Then you look to couples of letters, for example et, at, th, etc, and finally you can break the code.