substitution

Substitution cipher

This program encrypts a plain text message using the substitution cipher.

Usage

The program takes in 1 command-line argument, an integer, as the cipher key. The plain text message input will be requested after the program is run.

The argument should be a 26 character string with no repeated characters. From the CS50 documentation:

A key, for example, might be the string NQXPOMAFTRHLZGECYJIUWSKDVB. This 26-character key means that A (the first letter of the alphabet) should be converted into N (the first character of the key), B (the second letter of the alphabet) should be converted into Q (the second character of the key), and so forth.

Usage examples

$ ./substitution JTREKYAVOGDXPSNCUIZLFBMWHQ
plaintext:  HELLO
ciphertext: VKXXN

$ ./substitution VCHPRZGJNTLSKFBDQWAXEUYMOI
plaintext:  hello, world
ciphertext: jrssb, ybwsp