The Z408 cipher really was first solved by the Hardens. It was sent to the Navy who declined to work on it. It was then sent in to the FBI after the Hardens solved it, and the FBI solved it independently and confirmed that the solution was correct. You are aware that someone else sent in a code key a few days after the Hardens? There is speculation that was from the Zodiac himself, but we don’t know. It was most likely just someone else who came up with the solution, or made a copy of the Hardens for ease of reference.

The idea that they withheld the solution for security reasons is a new one, but not correct. The usual story is that the authorities were simply too stupid to solve it, which is a myth that was originated in Graysmith. The reality is that they never really tried, and it was easily solved in a few days by the couple.

Yes, what duck said.

Might add that as far as the inscription is concerned the likeliest meaning of it is simply that B. Harden expressed a desire to solve the 340: In a sense she started the thing (by revealing Zodiac as we know him, through solving his cipher), and she wanted to end the thing too (by solving the 340, in which Zodiac – as she hoped – would reveal his identity).

People have speculated wildly about this, to the point where Bettye and her husband have been launched as "POIs" in the case. I have no time for that myself.

I can understand that people are reluctant to consider that the Hardens may have been more involved; I currently have no opinions either way.
I do find it incredible that they solved it so quickly and; as far as we’re aware; other ciphers remain unsolved but I can’t rule anything in or out; all very intriguing!

The short answer is that the Z408 is pretty simple, while the Z32 and Z13 are unsolvable based on what we currently know. They are simply too short to be able to detect a meaningful pattern. There are in fact thousands of solutions that fit, and it’s impossible to tell which one would be the intended message.

As for the Z340… You could say a lot. It hasn’t been solved because it’s possibly quite a bit more complicated than the Z408. Beyond the cipher work itself, it always struck me that Zodiac went to the trouble of making them, and apparently seemed to not care one bit whether they were solved or not. That’s part of the whole mystery.

I think the bottom line is that the 408 isn’t all that complex: If they had put a team of experienced navy code breakers on it, they probably would have solved it faster than the Hardens.

That the 408 is super complex and that it’s therefore fishy that the Hardens managed to solve it (where the professional code breakers failed) is simply a myth: It didn’t happen that way.

Norse is correct. The Z408 cipher – and others of the same type – can now be solved in mere seconds by computer programs. The Z340 is an entirely different animal, so to speak.

-glurk

The progression of the ciphers is confusing to me. Are we to believe the murderer or his accomplice started with a cipher which could easily have been created and solved and rapidly progressed to creating ciphers which could not be broken by experts? He established his capabilities with the initial cipher and they aren’t very impressive. Is it possible the subsequent ciphers can’t be solved because they are meaningless?

The progression of the ciphers is confusing to me. Are we to believe the murderer or his accomplice started with a cipher which could easily have been created and solved and rapidly progressed to creating ciphers which could not be broken by experts? He established his capabilities with the initial cipher and they aren’t very impressive. Is it possible the subsequent ciphers can’t be solved because they are meaningless?

This is what I think. There was no incentive for Z to send ciphers that could be solved, thus making the solvers appear smarter than him. There was every incentive to make sure they would never be solved. I think the Hardens embarrassed him… he likely, in my opinion, made sure that could never happen again.

The progression of the ciphers is confusing to me. Are we to believe the murderer or his accomplice started with a cipher which could easily have been created and solved and rapidly progressed to creating ciphers which could not be broken by experts? He established his capabilities with the initial cipher and they aren’t very impressive. Is it possible the subsequent ciphers can’t be solved because they are meaningless?

it’s more likely that he added a non-conventional step when enciphering. the weak point of most encryption techniques is you’re trying to hide the message from most people but you want at least one other person to be able to decrypt it. that means there has to be a decryption method and most of the time this follows some series of steps known in advance by both parties. zodiac had already been embarrassed by a mom and pop duo revealing his message (which was also revealed to mostly be nonsense). it’s entirely likely that he changed his technique to add some random step that we’d have to correctly guess at to aid in decryption. if, for instance, he randomly added nulls to the message it’s unlikely to ever be properly decrypted. obviously this would be a dumb step to take if you actually wanted someone to decrypt it because you’d have to explain the randomness of those values thus negating their effectiveness.

it’s more likely that he added a non-conventional step when enciphering. the weak point of most encryption techniques is you’re trying to hide the message from most people but you want at least one other person to be able to decrypt it… if, for instance, he randomly added nulls to the message it’s unlikely to ever be properly decrypted. obviously this would be a dumb step to take if you actually wanted someone to decrypt it because you’d have to explain the randomness of those values thus negating their effectiveness.

Right, so it comes down to: Did Z want someone to decrypt it? If someone did (or does) that person wins and proves himself smarter than Z because it’s far easier to create a cipher than to solve one. Or, did Z, having been beaten and embarrassed once, make sure he would be the winner in the future?

My take on Z is that he wasn’t interested in playing a "fair" game. He was a pure control freak. Obviously I could be wrong, there may be some way to rearrange the symbols, or exclude some as nulls, or whatever, and find some meaningless message about how Z likes to kill people, but even then, what use would that be in solving the case? About the only value would be, if it is a legit cipher, it would show Z to be incredibly smart, but I think the odds of that are low.

I think the worthwhile clues are ones Z left by accident, not the ones he constructed for us.

Marshall….

I know the FBI do more cipher decoding training than anyone, and have used Z codes as part of their training portfolio for years. And the brightest minds in the business have taken their shots without any success. So to me, your theory has a lot of merit. It would be very Z like also to make up a cipher that looks legit, and yet he knows at the end of the game, it’s just Z gibberish, some busy work for police to do.

yeah, the guy was nuts. I mean he might not have had any mental impairment, but he did a lot of things that don’t make any sense.

Like his bus bomb diagram. I think we mostly agree that if he ever did build it, he didn’t really plant it anywhere. But he drew up that diagram and sent it in. Why? To make it more believable? Who cares? No one really cared anyway, and no bomb ever was known to go off, so it was just pointless. Yet that was something he put a lot of time and thought into, for no real reason.

he liked to scare and intimidate people. he liked to be in control. i think the 340 has a solution. i don’t think it’s one anyone but zodiac is likely to find. i think the guys and gals on here who are working to decrypt it are amazing people who probably have the best chance of stumbling into the "a ha, that’s what he did" that it would take to do so. i still think that’s a long shot because it’s so easy to make a cipher that no one can solve.

I tend to think of the bomb diagram as, for lack of a more precise term, cartoonish: He wanted to come across as someone who knew how to construct a death machine, thus adding another string to his bow. He played around with the concept of a – say – super villain, someone who mastered all kinds of fiendish arts, from shooting people with electric gun sights, via complex ciphers, to constructing bombs with ingenious trigger mechanisms.

The motivation for the ciphers lies somewhere within that spectrum for me: It added to the mystery, boosted his notoriety, etc. Everything he did may not be explainable in that light, but I believe everything he wrote can be placed in that category.