Caesar cipher
A classical substitution cipher.
Shift every letter of a message by a fixed amount and you have the Caesar cipher, which Julius Caesar used for military orders. With only 25 possible shifts, it is also easy to break.
Plain
Cipher
Try it
Shift
3
Plaintext
Ciphertext
KHOOR ZRUOG
Breaking it
Try every shift until one reads as English. This is called brute force.
Challenge
TF MHCVBYPAL JOLZZ VWLUPUN PZ AOL JVSSL GBRLYAVYA
What does this say? Try all possible shifts below. One of them will be readable English.