Throughout history, information has been the most valuable resource to mankind: in technological research, exploration and even war. Therefore, those in power have often sought methods to prevent their enemies from reading the messages that they send.
Hence, humanity developed encryption, the process of turning a plantext, readable message into unreadable cipher text. Below are two simple substitution ciphers. (More coming soon)
This is the most basic of substitution ciphers, used by Julius Casear himself at around 50BC, where each letter in a message is shifted a certain number of places down the alphabet by a fixed key.
This is a slightly more complex substitution cipher that uses a mathematical function in the form e(x) = ax + b to encrypt each character (mod 26). Consider that the coefficent of x must be coprime with 26 otherwise multiple characters will be mapped to the same letter.