In this all characters of plain text is replaced by other characters with same pattern.
A Caesar cipher is a simple method of encoding messages. Caesar ciphers use a substitution method where letters in the alphabet are shifted by some fixed number of spaces to yield an encoding alphabet. A Caesar cipher with a shift of 1 would encode an A as a B, an M as an N, and a Z as an A, and so on.
Cryptosystems use a set of procedures known as cryptographic algorithms, or ciphers, to encrypt and decrypt messages to secure communications among devices and applications.
Algorithm
Choose a value to shift the alphabet by.
Make a table where the top row contains letters in standard alphabetical order, and the bottom row is the new shifted alphabet.
Encode the message by exchanging each letter in the message with the equivalent shifted letter.
Make sure that the message’s intended recipient knows the shifting scheme you used to encode the message so they can decode it.
To decrypt a message encoded with a Caesar cipher, simply take the value of 26 minus the shift value, and apply that new value to shift the encoded message back to its original form.
A public key associated with the creator/sender for encrypting messages and a private key that only the originator knows (unless it is exposed or they decide to share it) for decrypting that information.