I'd like to get back into writing C, so I'm just throwing some basic stuff together to warm up to it.
A super basic project that encrypts with the Caesar Cipher I'm using a right-shift of three (the one Julius Caesar used). Lowercase letters get shifted into lowercase, same with uppercase. Non-letter characters ignored! Csar reads a message.txt file and prints the encrypted text.
The [Vignère Cipher] (https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher) is a variation on the Caesar cipher. Instead of hacing a constant offset, each character's offset is determined by a corresponding letter of a key. So, a key "foo" would offset by 6, then 14, then 14, then back to 6, until the original text has been enciphered.