Monoalphabetic ciphers

Crypto is from the Greek kryptos, meaning hidden or secret. Cryptology is the study of secrecy systems, cryptography, the design and implementation of secrecy systems, and cryptanalysis, the study of systems or methods of breaking ciphers. The message to be altered into secret form, the message we want to send, is called the plaintext. The message we actually send is called the ciphertext. The device used to transform the plaintext into the ciphertext is called a cipher. Plaintext and ciphertext may be composed of letters, numbers, punctuation marks, or other symbols. Encryption or enciphering is the process of changing plaintext into ciphertext. Decryption or deciphering is the process of changing ciphertext back into plaintext. In order to make decryption more difficult, plaintext and ciphertext are often broken up into message units of a fixed number of characters. The enciphering transformation can be thought of as a one-to-one function that takes plaintext message units into corresponding ciphertext message units. The process or method used in going from the plaintext to ciphertext and back to the plaintext is called a cryptosystem. A cipher is called monoalphabetic if it uses only one cipher alphabet.