Caesar Cipher/ROT 13

Caesar Cipher

The Caesar Cipher or Caesar Shift is a cipher which uses the alphabet in order to encode texts. The idea is to encode each letter with another letter in a "fixed" set of shifts.

Info

CAESAR encoded with a shift of 8 is KIMAIZ so ABCDEFGHIJKLMNOPQRSTUVWXYZ becomes IJKLMNOPQRSTUVWXYZABCDEFGH

Breaking a ciphertext is incredibly easy as there are only 25 possible "shifts" in the English alphabet.

Bruteforce?

We can use a tool like cyberchef to do this quickly but can also print out all the combinations in Python.

secret = "iwtgt xh cd gxvwi pcs lgdcv. iwtgth dcan ujc pcs qdgxcv.".lower()
for i in range(0, 26):
    decrypted_string = ""
    for j in range(0, len(secret)):
        letter = ord(secret[j])
        if (letter > 122) or (letter < 97) or secret[j] == " ":
            continue
        else:
            letter += 1
            if letter > 122:
                letter = 97
            letter = chr(letter)
            decrypted_string += str(letter)  
    secret = decrypted_string.strip()  
    print(decrypted_string)

#output
#...
#thereisnorightandwrongtheresonlyfunandboring
#...

ROT13

ROT13("Rotate 13") is the same thing but a fixed shift of 13, this is a trivial cipher to bruteforce because there are only 25 shifts.

Generally, Caesar's Cipher and ROT13 are used in conjunction of other encryption methods to make the challenge more difficult!