SCIENTIA · POTESTAS

Caesar · Cipher · Challenge

Decrypt the message · Earn the laurels
Rolling Thunder Security · Symmetric Encryption
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The Decoder
SHIFT No shift
CIPHER
PLAIN
↑ Read your ciphertext letter on top, then look directly below for the plaintext ↓

The Caesar Cipher

Named for Julius Caesar, who used it for military communication, the Caesar cipher is a substitution cipher where every letter in the plaintext is shifted a fixed number of positions in the alphabet. A shift of 3 turns A into D, B into E, and so on. There are only 25 possible non-trivial keys (K = 1 through 25), which is why brute-force attacks crack it instantly.

Encryption vs. Decryption Direction

The encryption key K shifts each plaintext letter forward by K. To decrypt, you shift each ciphertext letter backward by K, which is the same as shifting forward by 26 - K. So for K = 5, decryption is "left 5" or equivalently "right 21." The wheel below lets you try both directions until the message reads correctly.

How to Play

You'll be given an encrypted message. Use the decoder strip below it: the top row is the cipher alphabet (movable), and the bottom row is the plain alphabet (fixed). Slide the top row left or right until your ciphertext letters on top line up with sensible plaintext letters on the bottom. Type your answer and submit.

Scoring

Easy puzzles are worth 10 points, Medium 20, Hard 30, ZZZ Lore 25. Each hint deducts 5 points (minimum 1 point). Build a streak for bragging rights.

Keyboard Shortcuts

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