This is the first of a series of cipher challenges published at regular intervals. After much deliberation, I settled upon a 28-day cycle, for the benefit of both werewolves and pre-menopausal women alike. It is also a convenient multiple of the seven-day week invented by the Mesopotamians (yes, I know what you’re thinking: they usually adopt a sexagesimal system for time, money, distance etc.). Henceforth, the Tuesday immediately prior to the full moon shall be termed Cipher Tuesday.

Strictly speaking, the lunar month is inevitably slightly different from 28 days, so Cipher Tuesday will eventually become out of phase (no pun intended) with the Moon. I’ll be writing a post on lunisolar calendars, continued fractions and the LLL lattice reduction algorithm in the foreseeable future, but until then this crude approximation will suffice.

Anyway, the puzzle. I wrote a message of 336 characters, enciphered it and wrote it on a completed 336-piece jigsaw. I then proceeded to disassemble the jigsaw and randomly rearrange the pieces. Actually, I told Wolfram Mathematica to do the same; it has much more patience than I do. The result is a two-stage puzzle, the *Jigcypher*. There is a reason for the archaic British spelling, but I prefer not to divulge it at this stage.

Clicking on the above image will link to a full-size PNG of the *Jigcypher*. You could print it off on A4 card for a more tactile version; being the order of PGL(2,7), 336 has many factors so there are plenty of ways to evenly partition the pieces into sheets of equal size. Six sheets of 56 pieces should work nicely. Alternatively, you could assemble the entire jigsaw in MS Paint or some other graphics program. I’ve used lossless compression (PNG) to retain the perfectly solid white background for this purpose. The pieces are all in the correct orientation, as you can discern from the Greek letters on the (non-empty) tiles.

I have nothing more to say on this topic, apart from a terrible cryptanalysis-based pun: ‘Get cracking!’

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