Explain at length what a Caesar cipher does.

Question

What will be an ideal response?

Answer 1

A Caesar cipher, also called a shift cipher, involves shifting each character in the message to another character some fixed distance farther along in the alphabet. Specifically, let s be some integer between 1 and 25 that represents the amount of shift. Each letter in the message is encoded as the letter that is s units farther along in the alphabet, with the last s letters of the alphabet shifted in a cycle to the first s letters. For example, if s = 3, then A is encoded as D, B is encoded as E, X is encoded as A, and Z is encoded as C. The integer s is the secret key. Decoding a message, given knowledge of s, simply means reversing the shift. For example, if s = 3, then the code word DUPB is decoded as ARMY. The Caesar cipher is an example of a stream cipher; that is, it encodes one character at a time. This makes it easy to encode just by scanning the plaintext and doing the appropriate substitution at each character. On the other hand, there are only 25 possible keys, so a ciphertext message could be decoded by brute force, that is, by simply trying all possible keys. In addition, the Caesar cipher is a substitution cipher, whereby a single letter of plaintext generates a single letter of ciphertext.