Encrypting a message

The Caesar Cipher is a simple substitution cipher which replaces each original letter with a different letter in the alphabet by shifting the alphabet by a certain amount.

SECRET MEETING AT THE PALACE

To make the encrypted message above, I shifted the alphabet by 6 and used this substitution table

Here’s what that might look like encrypted:

YKIXKZ SKKZOTM GZ ZNK VGRGIK

Decrypting a message

According to historical records, Caesar always used a shift of 3. As long as his message recipient knew the shift amount, it was trivial for them to decode the message.

EHZDUH EUXWXV

The comrade uses this substitution table, where the alphabet is shifted by and They can then decode the message with certainty. The first letter “E” was shifted by 3 from “B”, the second letter “H” was shifted by 3 from “E”, etc. The result is this ominous message:

BEWARE BRUTUS