It’s an interesting question. I’m sure I’ve seen some posts on this – or something similar – either on here or on one of the other boards, i.e. something about "popular" (all is relative) books on the subject in the 60s. You could try searching on Voigt’s or Butterfield’s boards, for instance.

I’m not sure that Z ever studied anything very fancy, however. The 408 certainly didn’t require any in-depth knowledge of the subject. He could have read Poe’s "The Gold Bug" in school – or just picked up something about basic substitution ciphers…anywhere, really.

The question is – as it’s always been – whether the 340 is a genuine step up from the 408, i.e. a properly constructed but significantly more complex cipher, or whether the fact that it’s never been solved is down to something else.

Great topic and very good question. How did Z learn about Ciphers.

One theory, I agree with, first published in the yellow book was that Z used this book:

1964’s Codes and Ciphers:
http://www.tobiasschroedel.com/img/book … k_0237.jpg

This is the book with the Zodiac Alphabet that has a few similarities to the 408:
http://farm2.staticflickr.com/1274/1310 … z.jpg?zz=1

https://en.wikipedia.org/wiki/Helen_Fouch%C3%A9_Gaines

Just sayin’

-glurk

EDIT: I think I have a copy of this book as a PDF file. It’s no longer in print, to the best of my knowledge.

EDIT 2: I do have it. I might share it, if asked nicely…

I was going to mention something of this nature last night. I just couldn’t understand why the poster would want to limit themselves to just the 1960’s.

Soze

These are all great books, but the question is – which one would Zodiac be most likely familiar with? How would he get a hold of one? These days, it’ easy – you can find most popular books online, and the rare ones – on amazon/ebay/etc.. In the ’60s I’m guessing you had to either got to a local bookstore, or a local library. What would be the selection of books on cryptography in an average San Francisco bookstore or library in the ’60s? Is it possible to find that out somehow?

These are all great books, but the question is – which one would Zodiac be most likely familiar with? How would he get a hold of one? These days, it’ easy – you can find most popular books online, and the rare ones – on amazon/ebay/etc.. In the ’60s I’m guessing you had to either got to a local bookstore, or a local library. What would be the selection of books on cryptography in an average San Francisco bookstore or library in the ’60s? Is it possible to find that out somehow?

I’m really surprised you haven’t asked for the eBook glurk offered.

Soze

This is the book with the Zodiac Alphabet that has a few similarities to the 408:
http://farm2.staticflickr.com/1274/1310 … z.jpg?zz=1

Unfortunately these appear to be just similarities. There are quite a few fairly easy signs he could have used from that table, but didn’t. For example, I can see Neptune sign, or Taurus, or Cancer, being simple enough and distinct enough to be used. But he instead chose to go with that "mirrored J" that can easily be confused with the capital I, and added dots to it. Did he invent that symbol by the way, or is it known for something?

My guess would be that any half decent bookstore back then would be able to order in whatever book you wanted provided it was available from the publisher. So if he knew what he wanted, he’d probably get it easily enough even if it wasn’t on the shelf.

As for what would have actually been on the shelf in an average bookstore back then – I have no idea. There are probably records, to some extent, but how to find them – again, no idea. Contacting the publishers, if they’re still in business, is probably where I’d start.

It would probably be easier to find out which crypto books an average public library offered at the time – you may find that out by simply contacting your local library.

Another possibility is to contact a cryptography guy (or girl) at a university – and simply ask them for help: Do they know which books were commonly available back then – and if not, do they know any old geezers you can contact.

By the way, is that 47 in your avatar?

Trying to figure out which book Z might have been familiar with is probably a dead end after all. I was just thinking there could’ve been a popular fad around that time that would have narrowed it down to one book. Something like "The Da Vinci Code" or "50 Shades of Grey" of his time, but about cryptography. Or a movie, like "The Imitation Game". Doesn’t seem to be the case…

By the way, is that 47 in your avatar?

47? Don’t know what you mean. I just used the first image that jumped at me on my computer’s desktop, which happened to be the icon for The Stanley Parable game. 🙂

Who’s old avatar is it reminding me of? Morf was it yours from ZKF years ago except in blue?

There is a book called Secret and Urgent which the Harden’s used to solve the 408.

I find it interesting in relation to the Harden’s and also because of a reference from Wikipedia about a special case of rail fence (Zigzag cipher): https://en.wikipedia.org/wiki/Rail_fence_cipher

Zigzag cipher
The term zigzag cipher may refer to the rail fence cipher as described above. However, it may also refer to a different type of cipher system that looks like a zigzag line going from the top of the page to the bottom. As described in Fletcher Pratt’s Secret and Urgent, it is "written by ruling a sheet of paper in vertical columns, with a letter at the head of each column. A dot is made for each letter of the message in the proper column, reading from top to bottom of the sheet. The letters at the head of the columns are then cut off, the ruling erased and the message of dots sent along to the recipient, who, knowing the width of the columns and the arrangement of the letters at the top, reconstitutes the diagram and reads what it has to say."

47? Don’t know what you mean. I just used the first image that jumped at me on my computer’s desktop, which happened to be the icon for The Stanley Parable game.

Agent 47. Video game character.

I find it interesting in relation to the Harden’s and also because of a reference from Wikipedia about a special case of rail fence (Zigzag cipher): https://en.wikipedia.org/wiki/Rail_fence_cipher

Zigzag cipher
The term zigzag cipher may refer to the rail fence cipher as described above. However, it may also refer to a different type of cipher system that looks like a zigzag line going from the top of the page to the bottom. As described in Fletcher Pratt’s Secret and Urgent, it is "written by ruling a sheet of paper in vertical columns, with a letter at the head of each column. A dot is made for each letter of the message in the proper column, reading from top to bottom of the sheet. The letters at the head of the columns are then cut off, the ruling erased and the message of dots sent along to the recipient, who, knowing the width of the columns and the arrangement of the letters at the top, reconstitutes the diagram and reads what it has to say."

Don’t believe everything you read on Wikipedia. 🙂 What they are describing there is actually called the "Dot code" as the ciphertext looks like a bunch of dots, one per line/row (or one per column, if the ciphertext was rotated 90 degrees). It has nothing to do with rail fence, and I’m not even sure why they made the connection to "zigzag". Here’s an example from Gardner’s book "Codes, Ciphers and Secret Writing":