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Autokey from the rail
Hard. Autokey Vigenère. Primer RAIL, then the plaintext itself becomes the rest of the key. Spaces stripped.
Puzzle editor
Cipher
Ciphers desk
Cipher sets the puzzles on the Ciphers page, with 47 so far. They range from classic codes like Playfair, Vigenère and Pigpen to logic puzzles, word searches, mini crosswords and quick quizzes, and many are themed on the news, from Starship's chopsticks to Cold War spies. The answers sit at the end of each puzzle, held back until you want them.
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Beaufort on the Gulf
Medium. Beaufort cipher, keyword STAR. Same operation encodes and decodes.
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Bifid in the factory
Hard. Bifid cipher. Keyword TESLA, period 5, I/J share.
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Digits on the invite
Medium. Gronsfeld. Like Vigenère, but the key is digits. Key 2014. Spaces honest.
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Flags on the pad
Easy. Semaphore. Flags as clock positions, letters A–Z around the circle.
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Bacon on the desk
Medium. Baconian cipher. Five a/b symbols a letter. A=aaaaa.
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Five and eight
Medium–hard. Affine cipher. E(x) = (5x + 8) mod 26. A=0.
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Five by five, good news
Easy–medium. Polybius square. I and J share a cell.
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Pigpen at the chopsticks
Easy. The old Masonic alphabet. One word.
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Playfair, Tesla
Hard. Playfair square. Keyword TESLA. I/J share. X fills doubles.
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Read the columns, rail
Medium. Columnar transposition. Keyword RAIL.