Worked examples
Affine cipher
Encode HELLO one letter at a time, then use the same keys to decode RCLLA.
Open Affine cipherCipherSteps
Learn how ciphers work
Follow worked examples of Caesar, Vigenère, Rail Fence, and more. See each calculation, then try a short exercise yourself.
Worked examples
Caesar cipher
Watch shift 3 turn HELLO, WORLD! into KHOOR, ZRUOG!, then reverse each step.
Open Caesar cipherWorked examples
Columnar Transposition
Find the column lengths before decoding a grid with an incomplete last row.
Open Columnar TranspositionWorked examples
Morse code
Count the tones and gaps in three separate Morse letters: S, O, and S.
Open Morse codeWorked examples
Playfair
Follow the extra X in BALXLOON and see why a decoder leaves it in place.
Open PlayfairWorked examples
Polybius Square
Trace JIG through the I/J square and see which spelling detail the code loses.
Open Polybius SquareWorked examples
Rail Fence
Trace a three-rail zigzag, count the letters on each rail, and put the message back together.
Open Rail FenceWorked examples
Vigenère cipher
Line up LEMON with ATTACKATDAWN and follow every letter of the result.
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Cipher rules and reference guides
Look up alphabet rules, valid keys, Morse timing, and the information each method can recover.