This is one of the oldest ciphers, said to have been used by the Roman politician Julius Caesar to send commands to his army. A becomes D, B becomes E... That is all there is to it: shift each letter of the alphabet by a fixed number of positions. Turn the wheel and try encrypting and decrypting a message yourself.
Encryption: Shift each original letter forward by the shift amount (for example, if shift=3, A→D). Decryption: Move the letters backward by the same amount. On the wheel below, change the shift value by moving the slider, and see how the letters on the outer and inner circles are paired.
shift (number of positions)3
🔒 Encrypted result
🔓 Decrypted again (using the same shift)
⚠️ There are only 26 possible shifts, from 0 to 25. So a computer can try them all in less than a second — that is why the Caesar cipher is not secure in practice. Modern ciphers such as RSA have more possible combinations than there are atoms in the universe, so this approach does not work against them.