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.

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. 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

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:

An 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. 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.

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). 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.

Cryptanalytically, 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. In fact, if you colour all the Z13’s repeated cipher shapes (again, once using Dave Oranchak’s neat-o-rama Cipher Explorer), this is what you see:

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. 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.

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. So there would seem to be something a little odd going on here, cryptanalytically speaking: something feels wrong.

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 [Hollywood] Hills):

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. Giving MAD Magazine’s “Alfred E. Neuman” as his name feels like this exactly the kind of thing the Zodiac Killer would do, in that it is taunting, unhelpful, superior, nasty, satirical, self-centred, and narcissistic in all the right ways.

For ALFREDENEUMAN to be the Z13’s plaintext, the only concession you would need to make is that a single letter was misenciphered: and as starting points go for a ciphertext that already feels as though it has too few shapes, this is not half as big a step as almost all other solutions I’ve seen proposed. Even though I completely accept that this isn’t cast-iron proof, I do think it suggests that it is well worth considering as a conditional piece of evidence to work with.

And Now, The Z340 Cipher…

For me, the big (if not ‘huge’) question the above leads to is this: if this ALFREDENEUMAN Z13 decryption is actually correct, might the Zodiac Killer have included exactly the same name in his Z340 cipher? And if so, might we be able to use the name as a known-plaintext crib into the Z340? (AKA a block-paradigm match. 🙂 )

Assuming the Z340 does use some kind of homophonic cipher, there are (340 – 12) possible positions the Z13 crib could be positioned at: however, we should be able to eliminate any position containing a cipher shape repeat within the 13-shape stretch that does not match a repeat in the ALFREDENEUMAN crib, because that would mean that the same homophonic cipher shape would have been used to encipher two different plaintext letters.

For example, because Z340 line #4 begins “S99…”, the “99” part could not be any part of the Z13 crib because there are no doubled letters in “ALFREDENEUMAN”: this is also true for the “++” pairs in lines #4, #14, and #18. Similarly, the +..+ repeat on line #9 and the W..W repeat on line #18 both cannot be in the crib, because no plaintext letter is repeated three steps apart in “ALFREDENEUMAN”. If you run this against the most widely used Z340 transcription, there are – according to the vanilla C test I put together (below, which you can actually run for yourself by clicking on [Run]) – exactly 197 valid crib positions. So we can eliminate (340-12-197) = 131 candidate positions. Which is nice. 🙂

What I find interesting is that locking a set of fixed set of letters to an (albeit still hypothetical) crib should enable us to use a homophonic solver on far smaller subsections of the Z340 than we would normally be able to do. I’ve written before about how the top half and the bottom half of the Z340 have quite different (but subtly overlapping) properties: for example, how top-half ‘+’ characters seems to work differently to bottom-half ‘+’ characters. As a result, I think it would make sense to try to solve lines #1 to #9 separately from lines #11 to #19.

But there are other results, that point out how lines #1 to #3 seem to work quite differently from lines #4 to #6, and so on. So the ability to try to solve even smaller blocks of lines may well be a critically useful string for our cryptological bow.

Unfortunately, I’m not (yet) a zkdecrypto-lite power-user, so I don’t know how to automate this kind of search Anyone who would like to collaborate on doing this, please feel free to step forward: or if you want to take the idea and do what you like with it, that’s fine by me too. Can you blame me if I want to see this solved before they start shooting Season #2? 😉

Just One Last Thing…

There is, of course, one other possibility that should be investigated… it’s just that those cold, creepy eyes in the famous Zodiac poster remind me of someone, can’t think who it is, but the name might come to me soon, who was it…?

C: Crib Matching Code

Without any further ado, here’s The History Channel’s “The Hunt for the Zodiac Killer” season #1 finale, wherein Craig Bauer, having immersed himself almost completely in Zodiac Killer arcana, conjures up a new solution of the Z340, whereupon everyone else falls (or seems to fall) in line:

Well… OK, I guess. I suspect what most people would agree on about this ‘solution’ are:
* it’s primarily intuitive, and not really ‘cryptological’ in any useful sense of the word
* it’s either really brilliant or really foolish, and almost certainly nowhere inbetween

Craig’s Crack

Because the starting point for Craig Bauer’s decryption attempt was the idea that some letters might actually encipher themselves (to make the answer hide in plain sight), I’ve added a green background to those letters (or simply transformed letters) where the ciphertext and his decrypted text coincide, e.g. “HER……KI.L….” on the topmost line. You should be able to see 23 green-backgrounded letters.

However, for the sake of balance, I’ve also added a red background to those letters (or simply transformed letters) where the two do not coincide, e.g. “…PLVVP….TB.D” on the topmost line. You should be able to see 61 red-backgrounded letters (I think).

To make the following diagram, I used Dave Oranchak’s funky online Cipher Explorer tool:

It should be immediately obvious that a very high degree of selectivity is going on here: furthermore, seven letters are left out (on lines 2, 3, 5, 6 and 7), while three extra letters are inserted (lines 5 and 8). Finally, there is no consistent mapping of other shapes to plaintext letters as per the claimed decrypt, which is why I think it is safe to say that this is not a ‘cryptological’ decryption in any useful sense of the word.

The notion that a given historical ciphertext uses a handful of actual letters as themselves while the rest are somehow illusory or made up is an illusionary amateur cipher-breaking trope I have seen many dozens of times. In every case, it is a Pyrrhic victory of intense hopefulness over good sense, and achieves nothing bar wasting my time. If anyone can point my attention to anything about this particular decryption that varies from this rather self-defeating and useless template, I’d be fascinated to see it: but so far, this is just about as bad as it gets.

The motif of this antipattern is the codebreaker dreaming themselves an intense imaginary journey into the world of the codemaker, and bringing back as their prize a sampling of their vision, one that is every bit as hard to read as a book in a dream. All they have is the enduring conviction that they have solved it, a conviction that gets strengthened the brainier they are (and hence the more ingenious their post-rationalizing retro-fitting gets).

Total Immersion Delusion

If I were to give this kind of behaviour a “Pattern” name, I’d probably choose “Total Immersion Delusion“. Only someone who feels they have totally immersed themselves in their imagined world of the cipher maker would propose such a thing, and in almost every single case it is – sadly – a delusion that gets conjured up.

Here, you can see the seeds of the dream forming in the first line’s “HER…” and “KI.L” word-fragment patterns: but as the dream progressively fades away, the ability of the dreamer to fit the shape to the overselected letters reduces and reduces, until they’re left with only the sketchiest outlines of hope (a single green letter on lines 4, 5 and 7 demonstrates the degree to which it has triumphed over rationality here).

Sorry, but from what I can see, this Z340 ‘solution’ isn’t even close to being close: nobody’s going to come out of this particular dungheap smelling of roses, no matter how hard you hold your nose. Not huge, not a game-changer, sorry.

The new week brings a further episode of the History Channel’s “The Hunt for the Zodiac Killer”, not for the first time promising much but delivering little (Donna Lass car directions, really?) – the best part [37:25] was the interview with Zodiac Historian Misty Johansen (who wasn’t playing to CARMEL’s script). Even though it also partially revealed Craig Bauer’s much-trailed-and-supposedly-earth-shattering decryption of the Z340, that already looks to be more than a bit of a bust (sorry Craig), which I’ll discuss properly once the season finale has aired.

Things must be particularly bad when it takes someone on Reddit to nail it, but according to ‘chickendance638’:

if you made a drinking game where you drank when somebody said “game-changer” or “huge” then one could forget about the incredibly shitty tv show that’s just been viewed.

Though I’m pleased to say that the same commenter then proved sufficiently wise to the dangers of expressing even mild exasperated sarcasm on the Interweb by noting:

Gotta be careful, if it catches on I could be responsible for more deaths than Zodiac himself

Anyhoo, the Zodiac-Killer-associated cipher this week’s episode highlighted was a short ciphertext included in a letter sent to the Times Union in Albany, NY and postmarked August 1st 1973 (which Karga Seven’s handwriting expert duly affirmed was by the Zodiac Killer). So let’s do our collective codebreaking thing on the “Albany Cipher”…

The Albany Cipher

As always with everything Zodiac related, it’s important to say that the Albany Cipher had been discussed and debated by Zodiac researchers for many years before it appeared on the show. The clearest image we currently have to work with is…

…though this image of its cipher scanned from Lyndon Lafferty’s (2012) “The Zodiac Killer Cover-Up: The Silenced Badge” (p.427) may possibly be slightly clearer, but it’s hard to be sure because of the screening…

Incidentally, I emailed the Times Union’s archive people to see if they happen to have a photo of the letter in their files. They kindly replied that:

We do not have the letter and nobody here has any information on its whereabouts, the actual receipt of the letter and what happened to it.

Which is a shame, but it is what it is.

Cracking the Albany Cipher

As was made clear during Hunt Ep.4, the Albany Cipher was originally cracked by the FBI many years ago, though the version they released to the public had the very first part of the plaintext – presumably containing the non-victim’s name – heavily redacted. So far, this was a basically correct account, i.e. the programme makers didn’t yet again claim that the decryption was puked out by CARMEL.

What we have of the plaintext runs: xxxxxxxxxxxxALBANYMEDICALCENTRETHISONLYTHEBEGINNING. Even though it would normally be the case that having this many plaintext letters would force the rest of the ciphertext to be one of only a small number of possibilities, a number of things conspire to make this difficult here. For a start, a number of cipher letter shapes are very similar: moreover, the quality of the reproductions we have are not good enough to definitively tell them apart; while a third difficulty is that people’s names tend to be more variable and hard to pin down than ‘pure’ dictionary words. And so on.

From the letters we have, the cipher alphabet mapping looks something like this:

Using these, some of the letters in the name section seem quite solid: CONxxExxENLY. The closest single word (with a couple of ciphering slips) would be CONSEQUENTLY, but because that’s not a name, it doesn’t make sense in context. If you like Mexican food, you can also try to start it CON QUESA: but this also seems unlikely in context.

Which is why, back in 2013, Zodiac crypto-meister Dave Oranchak floated the idea that the name might possibly be CONNIExHENLY. (This is of course the same name that CARMEL supposedly suggested in 2017, *sigh*.)

But cryptologically, I’m not so sure that Dave was on the money here: given that there seems no obvious reason to think that the message contains homophones, we should surely not begin by accepting ‘N’ as the fourth plaintext letter, and, rather, should instead directly reject it. However, because most of the plaintext alphabet has already been allocated, the unique shape at position four must surely be an otherwise unused plaintext letter.

Moreover, there are patterns within the mapping layout: for example, I’ve marked up R/S/T with the same proxy cipher shape in the table because (frankly) I can’t tell them apart in the ciphertext, so they look to be part of the same shape family. Hence I wouldn’t be at all surprised if the same pattern was also used for adjacent letters Q or U. And finally, the closest visual match to the unknown fourth shape of the ciphertext is the shape used for Y: so I would be unsurprised if this letter stood in for an adjacent letter e.g. X or Z.

Put all this together: and if this is a name, my own best guess is that the first six letters are in fact “CONZUE” (short for “CONZUELA”). I’m sure Spaniards will be happy to tell me which part of Spain or South America “Conzuela” is typical of (or whatever).

Fans of Family Guy will (of course) know the name Consuela well:

Yes, it’s the famous “I clean toilet” sketch. 🙂

What would Consuela say about the Albany Cipher – does she think it was made by the Zodiac Killer? Only one possible answer: “No, no“. Well… either that, or “More Lemon Pledge“, you choose (and you pay). 😉

OK, I’m going to start this post by embedding S01E03 of the History Channel’s “The Hunt for the Zodiac Killer”, because this is what started me on the road to the solution to the Donna Lass cipher:

About half the episode is taken up with trying to make links between the Zodiac Killer and Donna Lass’s disappearance in 1970, a connection for which there seem to be two primary pieces of evidence – a poster (with a cryptogram) and a postcard. However, as we’ll see, it turns out that there are serious problems here which the series makers chose to fast-forward their audience past.

Who Was Donna Lass?

According to her FindAGrave website entry:

Donna was the daughter of James and Frances (Kukar) Lass. During high school, her activities included F.H.A. and singing in mixed chorus. During her senior interview, she stated that her plans were “to go college or be a nurse.” She was one the fifty-two members of the graduating class of 1962 at Beresford High School in Beresford, South Dakota.

Donna was listed as a survivor in the 1973 obituary of her father; but, she was listed as deceased in the 1982 obituary of her mother.

It’s hard not to conclude that hope for her survival died with her mother.

There are some reasonably good pictures of her on the Internet:

What happened to her? According to the official missing person’s page that discusses her:

Donna Lass was last seen in South Lake Tahoe, she left her residence without her vehicle or personal belongings. Lass worked as a nurse at the “Sahara Hotel-Casino”. Her last entry in the nurse’s log book was at 1:50 a.m., and although her car was found parked at her apartment complex in nearby Stateline, she wasn’t seen after leaving the Sahara.

The next day, an unknown male called her landlord and employer, stating Lass wouldn’t be returning due to a family emergency. The call was a hoax, and there has been no trace of Lass ever since

Of course, none of this sounds remotely like the Zodiac Killer’s modus operandi: so you’d have thought there really ought to be some good evidence out there linking the two, given the longevity of these claims.

The Donna Lass Cipher

The cipher first appeared on a reward-for-information poster, with each cipher shape underlined by hand. It’s unclear to me whether the underlining was originally designed in to the poster, or whether it was added by hand to the poster in the only genuine copy of the poster we have.

In episode S01E03 of “The Hunt for the Zodiac Killer”, the editing makes it seems as though everyone spends some time following a – frankly somewhat pathetic – interpretative anagram of the above cipher, that magically turns the cryptogram into driving instructions to get to some woods that just happen to have a TV-friendly creepy historical backstory (the Donner Pass cannibalism story, yada yada yada). In my opinion, this is right up there with people who draw pencil lines between similar letters and then try to convince you that it is not the cryptogram itself but rather those pencil lines that are the ‘real’ treasure map. *sigh*

Moreover, it was immediately clear to me (as I’m sure it was to everyone in the codebreaking team) that this particular reading wasn’t even close to being close: and, moreover, that the patterns of shapes were more or less exactly as you would expect a simple substitution cipher to present (for instance, the presence of doubled letters pointed directly away from any thought of Zodiac Killer-style homophones).

So once I’d got to the end of the programme, I found a copy of the cipher online and wrote it down on a piece of paper. Within ten seconds, I realized that the last set of shapes could only sensibly be DONNALASS: and that gave me enough letters to get to STALKING, and within a few minutes I also figured out that the larger phrase was I AM STALKING.

The next morning, when I ran a test to find words that fitted the pattern of the first six letters, only two words fitted – BEHAVE and BEWARE. Eliminating BEHAVE gave a nearly-complete decryption:


I then immediately felt a bit of a fool that I hadn’t immediately noticed that this was exactly the same as the start of the last sentence of the Riverside “Confession” letter: “BEWARE . . . I AM STALKING YOUR GIRLS NOW” (there’s a copy here):

After a little more thought, I became convinced that the first of the two outline triangle shapes at the start of the second line should probably have been an upside-down outline triangle, and that the original plaintext for the Donna Lass cipher was (without any real doubt):


Put all this together, and you’d have to say this looks like a cryptographic slam-dunk to link the crime to the Zodiac Killer’s “The Confession” letter (even if – in my opinion – he probably only tried to take ‘credit’ for Cheri Jo Bates’ murder, i.e. he didn’t do it himself). You can even see how the cipher shapes were laid out in a 5 x 5 grid by the encipherer, because the triangle shapes are all five letters apart, as are all the backwards letters.

However, it turns out that even though this is definitely the correct plaintext for this cryptogram, there are a number of issues

The Donna Lass Poster

The full poster looks like this:

For a start, it turns out that I was reinventing the wheel here (as far as solving this cipher goes). A number of other people had worked out the exact same plaintext a decade or more earlier than me – the earliest mention I found was May 2007: but given that it was so straightforward, it would be unsurprising if yet others had solved it long before then.

Problematically, commenter Seagull pointed out that:

The reward poster for Donna Lass, that Tahoe27 linked, can’t be from the ’70’s because the Area Code for the phone number did not come into being until 1997. […] Maybe this reward poster is from the time of Harvey Hines investigation.

Even Wikipedia lists this fact: “Created in 1997 by split from 916.” From that alone, there seems no chance at all that this poster was really from 1970 or 1971.

Moreover, commenter Slug then quickly pointed out (a) that the typesetting seemed inconsistent with the 1970s, and (b) that it seemed to have been laid out in close-to-exactly the same way that MS Word 97 would have done it. Others have also pointed out that it used Times New Roman, further compounding the period inaccuracy of the thing.

Finally, commenter Jupiter noted “a newspaper article about the Lass murder, written in 1971, that details a $500 reward put up by the family and people with information were to contact a private eye hired by the Lass family. There is no mention of having people contact the police with the info and the reward is considerably smaller”.

So where did the poster come from? Tom Voigt got it from Howard Davis, who in turn said:

Donna’s sister Mary sent that poster to me.It was done by the Lass family.

When asked about it, he then went on:

Mary mentioned to me a few times they had a family member(or in law) that is into computers,graphics,etc. He may have done the poster. She told me the reward was no longer in effect as I recall.Note at the bottom of the poster the family is mentioned.I do hope this doesn’t go into a all out contraversy as it was just an attempt at the time by the family to seek more information.I have enough to do as it is.Remember that Hines had pretty much convinced them Kane was the perp,hence,the ‘positive’poster wordage about having information,etc.

Put all this together, and the picture that finally emerges seems to be of the Zodiac theory industry collectively manufacturing a connection between Donna Lass and the Zodiac Killer – that is, Zodiac theorists convincing Hines so strongly that Laurence Kane (who Donna Lass personally knew) was the Zodiac Killer that he incited the Lass family to include a fake Zodiac-style cryptogram on a later faked-up poster.

The awful (and stupid) thing about this is that it encourages people to view the causality backwards: that while there is no doubt that Laurence Kane was connected to Donna Lass (and so could genuinely have been a person of interest), her sad death had absolutely nothing in common with any of the Zodiac Killer’s confirmed murders – the connection implied by the poster would seem to be totally bogus, in every sense of the phrase.

The Donna Lass Postcard

All of which process of elimination leaves us with the Donna Lass postcard, which the History Channel episode also trawled over for some time:

Well… after all the above discussion, it perhaps won’t come as any great surprise that there is a high chance that this postcard (which, let’s face it, contains nothing new about her death, nor proof of her murder, etc) is also fake:

A postcard, supposedly from Zodiac, was received by the San Francisco Chronicle on March 22, 1971, with the implication that Lass was a murder victim. However, the postcard contained no proof, as Zodiac was known for including. In 1999 a retired detective revealed to me that a former Zodiac investigator had admitted to forging the Lass postcard.

I’m sorry, but I have to say that I find this whole thing unbelievably sad. A vivacious young woman gets abducted (and, in all probability, killed) and all people want to do is to use her death to manufacture elaborate links falsely entangling it with a serial killer. What kind of vacuous, cynical theatre is that? This isn’t a cipher mystery, this is a cipher tragedy: shame on those who do such things.

A new day, and a new episode of “The Hunt for the Zodiac Killer” (S01 E02, in programme guide speak) to trawl through. Luckily, though, this week’s episode proved to be fairly lightweight:

Increasingly Uncomfortable

I’m sorry to have to say it, but as this series goes on, I’m getting less and less comfortable with the presentation. Televisually, the editing conceit has been to make it look as though all the evidence is being considered and discovered for the first time (and sort of ‘in real time’), but just about everything that pops up (hey, what magic beans has CARMEL found this time?) has previously been floated, shot down, raked over, partially resurrected and left hanging in a kind of evidential limbo ten or twenty times over. And so it’s more than a little bit grating to see so many creaky old ideas being dredged up and presented as if they were not only new, but also generated by a piece of software.

So, for all the potential cleverness of the software toolkit, CARMEL has been largely reduced here to a panto linking device, not a million miles from “And now for something completely different: a man with a tape recorder up his nose”. (Which, tape recorder reference aside, originally came from Blue Peter’s Christopher Trace, UK TV buffs might be interested to know.)

The connection the programme makers float between TWICH/TWICHED and SQUIRM/SQWIRM in the Cheri Jo Bates typed “Confession” letter and the Zodiac’s 1970 letter is interesting (of course, Michael Butterfield discussed this in 2009, though doubtless it was already old news by then). But in every other sense the Confession letter comes across to me as a crock, a simulation of a confession letter that says nothing actually new. And though two of the three notes that arrived six months later said that “BATES HAD TO DIE THERE WILL BE MORE Z”, these also come across to me as fakes, or rather someone simulating nuttiness.

At the same time, according to this Quester Files website page, “[t]he envelopes carried double postage. This is something the Zodiac did.” And moreover, “Sherwood Morrill, the Questioned Document’s examiner in Sacramento, examined the envelopes and writing. He said it was indeed The Zodiac’s handwriting.”

Putting all this together, even though I could comfortably accept the idea that the 1966 Cheri Jo Bates “Confession” letter and even the three (somewhat belated) nutty-looking handwritten notes were by the same person who would later become the Zodiac Killer, I would struggle to accept without any obvious supporting evidence the claim that he also killed Cheri Jo Bates, in the unquestioning way the programme makers seem to think their audience should. To me, it seems far safer to conclude that in 1966 Zodiac was instead merely fantasizing about killing, and that he instead wrote the suite of letters as a kind of performative role play theatre, projecting his incipient psychopathy onto the stabby, bloody, horrible backdrop of some other properly mad person’s crime (which was very probably driven by enraged sexual inadequacy and/or spurned passion).

Lone Wolf, or Sea Wolf?

As a side note, the question of the origin of the Zodiac and his ‘cross-hair’ symbol comes up again and again: an obvious issue is that his chosen symbol is not in any way connected with astrological or zodiacal symbols, which is also true of the (for the most part letter, reflected letter, and part-filled geometrical) shapes he uses in his ciphertexts. So, then: why ‘Zodiac’?

However, I have to say that the answer to this question seems to me to be very simple and indeed painfully obvious (though it has of course previously been pointed out a thousand times or more): that the most likely inspiration for the Zodiac’s symbol and name was the Zodiac Watch Company, which had during the 1950s achieved great renown with their Sea Wolf diving watch (and very similar symbol).

Note that the Zodiac Sea Wolf watch had (of course it did) a movable bezel, much as per the Mt Diablo note: which is not anything like proof, of course, but it’s definitely something to think about. (As a further aside, perhaps a watch historian might like to tell us which movable watch bezels of the 1960s had 0 / 3 / 6 / 9 markings on them.)

All of which finally spins this post back round again to poor Cheri Jo Bates’ murder: for, as the zodiackillerfacts site points out, it was there that “[I]nvestigators came upon a man’s Timex watch lying on the ground near the body”. Honestly, does anyone truly believe that a psychopath who specifically named himself after a macho Swiss watch brand would be seen dead – if you’ll pardon the phrase – in an American Timex?

The History Channel’s new Karga Seven-produced series “The Hunt for the Zodiac Killer” has just started: it features top Zodiac Killer researcher Dave Oranchak, Copiale Cipher cracker (and Voynich Manuscript fanboy) Kevin Knight, long-time Zodiac researcher (and University of North Texas CompSci professor) Ryan Garlick, Cryptologia editor (and author of “Unsolved!”) Craig Bauer, and a Google engineer guy called Sujith Razi who I’ve never heard of. But I’m sure is a lovely bloke.

The film makers also have a retired homicide cop and a cold case searcher both talking to people on the ground and raking over hitherto unseen archives. Overall, the televisual conceit they try to sustain is that the whole process is unfolding right before our eyes in sort-of real time, which is a decent enough fiction to structure this kind of thing by.

The first episode tries to link the Zodiac Killer with the unsolved 1966 Riverside murder of 18-year-old Cheri Jo Bates, a connection that has been floated (yet also denied) many times. The suspect they quickly move to is a certain Ross Sullivan, who was a student who also worked in the library where Bates was studying the evening of her death: Sullivan took a cryptography class, wore army boots, disappeared the day after Bates’ death, came back with fresh clothes a few weeks later, etc etc etc.

The programme alludes to DNA comparisons, to reconstructing faces purely from DNA, and to cracking some part of one the Zodiac Killer’s ciphers in the following episodes, but we’ll have to see which of these promises they keep. If all they ultimately serve up on their delightful silver platter is Craig Bauer’s ALFREDENEUMAN hopeful crack of the Z13 cipher (whose first three cipher letters are also “AEN”), I’m not 100% certain the cryptological ticker tape and marching elephants parade will be on duty that day. But, as always, we shall see.

Incidentally, my personal favourite of the homophonic solutions for the Z13 listed by Dave Oranchak are “Sarah The Horse”, “All Banana Alan”, and “Trove Behemoth”. Ever since I read that, I’ve been deeply distrustful of anyone called Sarah The Horse: I therefore advise all Cipher Mysteries readers to keep some sugar cubes in a convenient pocket, just in case this particular worst-case scenario is correct. What, me worry?

The Hunt for the Zodiac Killer

Anyway, I’m not sure how long the following embedded video will stay live for, but it’s courtesy of well-known site Tagtélé:

Enjoy! 🙂

When talking about the Zodiac Killer Z340 cipher, FBI cryptanalyst Dan Olson once pointed out that:

Statistical tests indicate a higher level of randomness by row, than by column. This indicates that the cipher is written horizontally and rules out any transposition patterns that are not strictly horizontal.

Here, while I’d agree with his observation part (the first sentence), I’m really not so sure about the conclusion part (the second sentence). And a little further on, Olson continues:

Row randomness of 408 is .22, 340 is .19. Column randomness of 408 is .48, 340 is .68. By way of comparison, row and column randomness should be near identical if the 340 does not contain any message, or if there is a message that is evenly scrambled.

This second time round, I’m comfortable with the observations here (the first two sentences), and mostly comfortable with Olson’s conclusion (the last sentence). However, I’d add that you have to be careful with his conclusion, because there is an implicit (but incorrect) follow-on conclusion lurking just beyond its limits for many readers: that if the cipher is not sequenced along columns, it must surely be primarily sequenced along rows of the text.

On the positive side, I would agree that we can conclude from this that we are not looking at a ‘pure’ periodic transposition cipher (i.e. one that rakes over the whole ciphertext, or even over the top or bottom halves). But what would it mean to assert that the Z340 is a bit more horizontal than vertical, though not as horizontal as the Z408?

An New Axis to Grind?

My (admittedly as-yet-hypothetical) explanation for all of the above is that what lurks behind is perhaps a short transposition cycle (i.e. no more than two or three elements long), where the elements are arranged across two or three consecutive lines, and where the end of each cycle steps back to the letter position immediately after the beginning of the cycle.

According to this, each ciphertext line would contain every second or third letter in the plaintext: for even though this would weaken the horizontal (row) adjacency patterning, it would not eliminate it. And statistically, this is essentially what we see: weakened horizontal patterning but no obvious vertical patterning. Because of the apparent groups of three lines (also noted by Olson), I suspect that these are arranged over three lines: and so this forms my primary hypothesis going forward.

A Quick JavaScript Test

I’ve posted up a quick JavaScript gist of what I’m talking about here:

The preliminary results of running this code fragment yields a different internal structure to each of the two halves (various intriguing results in bold):

Top half, first nine lines:
0: off2 = 3, off3 = 3, metric = 8
1: off2 = 2, off3 = 6, metric = 8
2: off2 = 2, off3 = 3, metric = 8
3: off2 = 0, off3 = 3, metric = 7

4: off2 = 3, off3 = 14, metric = 6
5: off2 = 1, off3 = 7, metric = 6
6: off2 = 0, off3 = 7, metric = 6
7: off2 = 3, off3 = 2, metric = 5
8: off2 = 2, off3 = 7, metric = 5
9: off2 = 2, off3 = 5, metric = 5

Bottom half, first nine lines:
0: off2 = 1, off3 = 0, metric = 10
1: off2 = 3, off3 = 11, metric = 9
2: off2 = 3, off3 = 10, metric = 9
3: off2 = 0, off3 = 4, metric = 9
4: off2 = 3, off3 = 15, metric = 8
5: off2 = 0, off3 = 8, metric = 8
6: off2 = 4, off3 = 8, metric = 7
7: off2 = 4, off3 = 4, metric = 7
8: off2 = 2, off3 = 15, metric = 7
9: off2 = 0, off3 = 10, metric = 7

Note that the period-19 (i.e. 17+2) effect is still slightly visible in the top half, but it’s much less apparent in the bottom half.

However, the most striking new pattern here is the (off2 = 1, off3 = 0) pattern in the bottom half, that yields ten pair matches in the untransposed text. This is the kind of zigzag transposition pattern one might expect of what Filippo Sinagra calls “peasant ciphers” – improvised amateur cryptographic tricks, that aim for security through obscurity.

Of course, I still have no idea whether or not I’m merely generating coincidences from the 17 x 17 x 2 = 578 permutations being examined here. But nonetheless it’s all quite interesting, right?

I’ve had the Zodiac Killer Z340 cipher on my mind for the last few days. Though I’m still finding it hard not to draw the conclusion that its top and bottom halves are two different ciphertexts (joined together for reason(s) we can only hazily guess at), what has drawn so much of my attention is a quite different class of statistical observation: letter skips.

Letter Skips

The most (in)famous example of letter skips was the Bible Code, made famous by Michael Drosnin’s (1997) book The Bible Code. However, this was merely one in a long line claiming that the Bible is not only the literal and exact Word of God, but is also an implicit encipherment of all manner of unexpected occult statements and prophecies. To get to these secret messages, all you have to do is read every nth letter, modulo length(Bible): and then, if you hunt through the vast swathes of near-random junk that emerges from that, you’ll eventually discover words, phrases, and proper names that couldn’t possibly have been known millennia ago when the Bible was first written down.

There have been plenty of mathematical and statistical dismissals of the Bible Code, almost all of which reduce to the simple argument that if you search enough random letter sequences for long enough, you’ll find something that sort of looks like text. And so when Drosnin huffed that “When my critics find a message about the assassination of a prime minister encrypted in Moby Dick, I’ll believe them”, his critics took it literally as a challenge. As a result, we now have lists of numerous Drosnin-style letter-skip ‘predictions’ in Moby Dick, along with a ‘prediction’ of Princess Diana’s death [thanks to Brendan McKay].

From which the moral unavoidably seems to be: be careful what you wish for.

Generated Coincidences

At the heart of the Bible Code lies a simple sampling fallacy: which is that if you perform a long enough series of arbitrary statistical analyses on the text of any given document, you will (eventually) uncover things in it which superficially appear extraordinarily improbable.

This is directly relevant to a lot of the Zodiac Killer code-breaking discourse because, broadly speaking, it is exactly what has happened there: diligent statistical enquiry has yielded not only millions of strike-out tests, but also a large number of (superficially) unlikely-looking patterns. And so the question is: if you perform a hundred different statistical tests and one of them happens to yield a pattern that only appears in one in two hundred randomised versions of the same document, have you (a) found something fundamental and causal that could possibly explain everything, or (b) just generated a coincidence that means nothing?

Sadly, there is no obvious way of telling the difference: all one can do is nod sagely and say, in the words of a great 1970s philosopher…


Transposition or “Tasoiin rnpsto”?

As should be plain as day from the above, I too view Bible Code letter skips as complete nonsense, and reserve my inalienable human right to cast a similarly cool eye over the impressive panoply of Zodiac Killer cipher observations, each of which may or may not be a generated coincidence.

Even so, utter disbelief of the specifics of the Bible Code shouldn’t mask the fact that the kind of statistical tests that are used for letter skips share a significant overlap with the kind of statistical tests that help reveal periodic ciphers and transposition ciphers.

Hence evidence of a letter-skip period in the Zodiac Killer Cipher should not be automatically put to one side because of the test’s association with hallucinatory Bible Code letter-skips, because evidence of a periodic effect could instead be pointing towards one of many other phenomena.

And there is indeed strong evidence of a period in play in the Z340, as first discussed by Daikon and Jarlve in 2015. Daikon examined the number of Z340 bigram repeats at different periods, and found a significant spike at period 19 (this really is noticeably larger than the other periods).

Here’s what these period-19 bigram repeats look like (was this diagram made by David Oranchak?):

Having then performed 1,000,000 random shuffles, David Oranchak concluded that this period-19 result had a “1 in 216” chance of happening. Which is good, but just a smidgeon short of great.

Incidentally, it’s easier to see these bigram matches if you rewrite Z340 in 19-wide columns (this diagram also probably made by David Oranchak):

More tests revealed all manner of similar periodic results that may or may not mean something: but I’m interested here specifically in the period-19 result.

Period-19? So what?

When he constructed the Z340, the Zodiac Killer had previously seen his Z408 cipher not only printed on the front page of newspapers (which surely pleased him), but also very publicly cracked (which surely displeased him). And yet his Z340 cipher closely resembles the Z408 in so many ways that it seems a fairly safe bet to me that his later cipher system was nothing more than a modification (a ‘delta’) of the earlier cipher system rather than something wildly different.

Hence I’ve long suspected that if we could somehow work out what the Zodiac Killer thought was technically wrong with the Z408 cipher system, then we could make a guess what his delta to the Z340 system might be.

Even though the Z408 presented all manner of homophone cycles, it wasn’t these that gave the game away to Donald Gene Harden and Bettye June Harden of Salinas. Rather, they made a number of shrewd psychological guesses (that the most likely first word a psychopath would write was “I”, and that the plaintext would include the word “KILL” multiple times), and used repetitions of “LL” as cribbed ways in to the message.

(As an aside, I struggle to believe that Bettye Harden genuinely guessed from scratch that the first three words of Z408 would be “I LIKE KILLING”, as has been reported. Instead, it seems far more likely to me that she had already worked for several hours on the cipher before making such an inspired guess.)

And so it seems most likely to me that the Zodiac Killer conceived his delta specifically as a way of disrupting the weakness of doubled letters (specifically doubled L), but without really affecting the rest of his code-making approach. And as always in cryptography, there are numerous ways this could be achieved:
* removing the second letter of all doubled letter pairs
* adding in new tokens for specific doubled letters (e.g. use ‘$’ to encipher ‘LL’)
* disrupt the order of the letters (i.e. transpose them) so that ILIKEKILLING becomes IIEILN LKKLIG etc

I’m therefore wondering if his cipher system delta was some kind of period-19 transposition. But – of course – people have already checked for the presence of straightforward period-19 transposition, and have basically drawn a blank. So if there is a period-19 ‘signature’ arising from some kind of transposition, it’s a little more complicated.

But if so, then what would it look like?

A three-way line dance?

My final piece of observational jigsaw in today’s reasoning chain is that the Z340 ciphertext is apparently arranged in groups of three lines. FBI cryptanalyst Dan Olson famously commented that…

Lines 1-3 and 11-13 contain a distinct higher level of randomness than lines 4-6 and 14-16. This appears to be intentional and indicates that lines 1-3 and 11-13 contain valid ciphertext whereas lines 4-6 and 14-16 may be fake.

…though note that this mixes up observation (the first sentence) with his best-guess inference (the second sentence). What I’m instead taking is that Olson’s observation more generally implies that lines are somehow grouped together in sets of three BUT with a spare line added in between the top and bottom half.

So, the overall line grouping sequence of the Z340 appears to be:
* top half: 1-1-1 2-2-2 3-3-3 X [a spare line with “cut marks” at either end of a fake line]
* bottom half: 4-4-4 5-5-5 6-6-6 X [a spare line with ‘ZODAIK’-like fake signature at the end]

Hence – putting it all together – I’m now wondering whether there is a period-19 transposition in play here BUT arranged in groups of three lines at a time. In which case, the symbol sequence for each set of three lines (3 x 17 = 51) might well look like this (where 01 is the first symbol of the plaintext, 02 is the second symbol, etc):

* 01 04 07 10 13 16 19 22 25 28 31 34 37 40 43 46 49
* 47 50 02 05 08 11 14 17 20 23 26 29 32 35 38 41 44
* 42 45 48 51 03 06 09 12 15 18 21 24 27 30 33 36 39

This transposition arrangement would yield both the period-19 effect and the groups-of-three-lines effect: and might also go some of the way towards explaining why lines 10 and 20 function differently to the other lines.

As I mentioned at the top of the post, I also strongly suspect that the top half of the Z340 and the bottom half of the Z340 are separate ciphertext systems, and so any solving should be attempted on the two halves individually, however inconvenient that may be. 🙂

I haven’t tested out this new transposition hypothesis yet: but it’s definitely worth a look, wouldn’t you think, hmmm?

Here’s the evidence that the Zodiac Killer is alive and busy with a spray can in Cyprus, visual documentary evidence to which only the most obtuse could possibly object:

And if you think that’s the most ridiculous and/or foolish cipher theory you’ve encountered in the last seven days, you obviously haven’t been paying much attention. 🙁

OK, so there’s like another Zodiac film coming out this summer (2017), and it’s like called Awakening The Zodiac. And if that’s not just like totally thrilling enough for you kerrrazy cipher people already, there’s also a trailer on YouTube long enough to eat a couple of mouthfuls of popcorn (maybe three tops):

I know, I know, some haters are gonna say that it’s disrepectful to the memory of the dead, given that the Zodiac claimed to have killed 37 people, and that the film makers are just building cruddy entertainment on top of their families’ suffering. But it’s just Hollllllllllywood, people, or rather about as Hollywood as you can get when you film it on the cheap in Canada. Though if the pitch was much more elaborate than “Storage Hunters meets serial killer”, you can like paint my face orange and call me Veronica.

Seriously, though, I’d be a little surprised if anyone who knows even 1% more than squat about ciphers was involved: if my eyes don’t deceive me, there certainly ain’t no “Oranchak” in the credits. Maybe there’ll turn out to be hidden depths here: but – like the Z340 – if there are, they’re very well hidden indeed.