Caesar cipher was earlier known as substitution cipher. Julius Caesar made its attested use in military affairs. Its core idea is to replace one basic unit (letter/byte) with another. It replaces each letter by third letter. For example:
PLAIN: meet me after the toga party
CIPHER: PHHW PH DIWHU WKH WRJD SDUWB
Monoalphabetic Cipher In this technique instead of simply moving the 26 alphabets, the letters could be rearranged discretionally. Each plaintext letter shows a different arbitrary ciphertext letter.
Play Fair Cipher
This technique does not provide enough security though large numbers of keys are used in monoalphabetic cipher. Numerous letters can be encrypted to deal with the security. Charles Wheatstone in 1854 invented this technique yet named after his companion Baron Playfair.
The general name for the approach to reduce the “spikyness” of the original language text is a polyalphabetic cipher. The playfair cipher encrypts more than one letter at once. The other alternative that can be considered is using multiple cipher alphabets in turn. In this technique, the attacker has to work hard since so many alphabets need to be guessed. Since the plaintext letter could be replaced by many ciphertext letters, the frequency distribution is very complex.
Every one of these procedures have the accompanying elements in like manner:
1. An arrangement of related monoalphabetic substitution