caesarCracker.c

/*
Caesar Cracker:
This program prints every possible Caesar Cipher
for a given input. It's primary use case is in
CTF or other "hacking" related competitions. Simply
look through the output for real words.

Written by Zachary Kline (www.ZachKline.us)
September 11, 2019
*/


#include <stdio.h>
#include <ctype.h>

void main(void) {
    char str[1024];
    int i, x;

    /* Accepts user input */
    printf("====================\nCaesar Cipher Cracker\nWritten by Zachary Kline\n====================\n");
    printf("Please enter a ciphered string (max 1024 characters): ");
    scanf("%[^\n]s", str); // The "[^\n] ensures that spaces are scanned in as well, so that you can paste in a whole sentence
    printf("\n");

    for (i = 1; i <= 26; ++i) {
        for (x = 0; str[x] != '\0'; ++x) {
            /*
            I had to make 2 separate if statements for
            whether the character was between a-z or A-Z
            so that we didn't accidentally start overflowing
            into numbers or symbols. This also had the added
            benefit of leaving numbers and symbols from the
            input untouched in the output.
            */
            if (str[x] >= 'a' && str[x] <= 'z') {
                str[x] = str[x] + 1;
                /*
                Next if statement corrects the output in
                case we accidentally fell outside of the
                alphabet by adding 1
                */
                if (str[x] > 'z') {
                    str[x] = str[x] + 'a' - 'z' - 1;
                }
            }
            /*
            This next if statement is just a copy of
            the previous one, but for the capital alphabet
            */
            if (str[x] >= 'A' && str[x] <= 'Z') {
                str[x] = str[x] + 1;
                if (str[x] > 'Z') {
                    str[x] = str[x] + 'A' - 'Z' - 1;
                }
            }
        }
        printf("+%d:\t%s\n", i, str);
    }
}