![]() Now, even though this doesn’t quite fit the pattern (the N cipher shape shouldn’t be shared between plaintext F and M), I think Bauer was completely right to give this his imprimatur, because it seems exceptionally close. In his 2017 book “Unsolved!”, Craig Bauer praised a possible crack of the Z13 cipher which I hadn’t previously heard of, and credits p.128 of Robert Graysmith’s (2002) “Zodiac Unmasked: The Identity of America’s Most Elusive Serial Killer Revealed” as the source (though Graysmith talks about it as if the suggestion were as old as the Hills): So there would seem to be something a little odd going on here, cryptanalytically speaking: something feels wrong. In many ways, whereas the problem with the Z340 is that it has too many shapes, the problem with the Z13 is arguably that it has too few shapes. Dave Oranchak’s “Laura Catapult”, and glurk’s “Gary Lyle Large” are fine examples of how it is possible to construct name-like phrases to fit: but these are relatively rare examples in a surprisingly sparse, errm, name-space. Much as I love “Sarah The Horse” and “Clara Cataract” as elegant literary plaintexts for this, it’s important to note that these are homophonic solutions for something whose many repeats point to its actually being a monoalphabetic substitution cipher. In fact, if you colour all the Z13’s repeated cipher shapes (once again, using Dave Oranchak’s neat-o-rama Cipher Explorer), this is what you see: Hence it seems entirely reasonable to conclude that the Z340 indeed contains a specific name for us to decrypt – though, as always, it seems highly unlikely that this will contain the Zodiac Killer’s actual name.Ĭryptanalytically, though, the Z13 couldn’t be further removed from the homophonic world of the (cracked) Z408 (and presumably the Z340), in that it has shape repeats and internal structure aplenty. However, if you put all these pieces together, it seems highly likely to me that it was instead the Z340 cipher that had been constructed as a response to President Marsh’s taunt (it appeared a mere seventeen days later). In the Examiner piece, entitled “ Cipher Expert Dares Zodiac To ‘Tell’ Name“, the President of the American Cryptogram Association issued a direct challenge to the Zodiac Killer to reveal his name in a cipher. The text just above the Zodiac Killer’s Z13 cipher (20th April 1970) clearly and unambiguously refers back to a ‘name’ supposedly in the Z340 cipher (8th November 1969), though as far as I can see the “Dripping Pen” note that arrived with the Z340 didn’t mention a name at all:Īn oft-repeated account for this is that the Z13 had been constructed in response to a kind of cryptographic ‘taunt’ that appeared six months previously in the Examiner newspaper on 22nd October 1969, as detailed here. ![]() But first I’m going to talk about the Z13 cipher, because I think it tells us a lot about what is hidden inside the Z340 and indeed why the Z340 was written at all… The Z13 Cipher In particular, I want to suggest an approach we might follow to try to solve the Z340 that (hopefully) won’t need a brain the size of a planet to run it. After The History Channel’s recent season of “The Hunt For The Zodiac Killer” programmes (episodes 1, 2, 3, 4 and 5), I thought it was time to get back to some non-fake-news codebreaking research. ![]()
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