Cabinet Noir
>Cryptoanalysis / Alberti cipher
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The first polyalphabetic cipher: two rotating discs switch alphabets every few letters.
Type
polyalphabetic substitution cipher
Breaking it
easy to break by hand
Era
15th century
Name
Devised by Leon Battista Alberti around 1467 on his cipher disk, Formula.
Modes
encrypt · decrypt · cryptoanalysis
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Tool
Cryptoanalysis
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History
Practice
Not the right cipher? Identify it
Ciphertext to break
Hints
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1. Period
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2. Disc step
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3. Done
The discs are the tool’s fixed ones, so the unknowns are the period and the disc step. Exact for ciphertexts whose plaintext letters all sit on the disc (like the practice challenges) — dropped letters shift the chunks otherwise.
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Created by Denys Grybov in 2021
v.0.4.0 // released on 18.10.2026