In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters, pairs of letters, triplets of letters, mixtures of the above, and so forth.

What is a shift cipher?

A shift cipher involves replacing each letter in the message by a letter that is some fixed number of positions further along in the alphabet. We'll call this number the encryption key. It is just the length of the shift we are using.

How do ciphers shift work?

Shift Ciphers work by using the modulo operator to encrypt and decrypt messages. The Shift Cipher has a key K, which is an integer from 0 to 25. We will only share this key with people that we want to see our message.