Updated Oct 17, 2014: Fixed the Google Drive link to the FBI files.

Diligent researcher morf13‘s persistence recently paid off: He received over 800 pages of never before seen material from FBI files on the Zodiac case. Click here to view all of the new documents (thanks, Mark, for uploading them). The files contain a wide variety of material related to persons of interest investigated for the Zodiac crimes. Inside the files you’ll see handwriting samples, letters, envelopes, crime reports, interview transcripts, emergency call logs, evidence analysis, and even a suspect’s day planner. The files also contain some unconfirmed Zodiac letters, and a lot of material related to Gareth Penn’s oft debunked theories about the killer and his codes.

This cryptanalyst’s conclusions about Gareth Penn’s strange code theories says it all:

Alas, that conclusion is reached all too often when analyzing the many claims that have emerged over the years.

And speaking of codes, here is one that appears in the files:

The files don’t seem to mention this code in any way. At first glance, it resembles a book cipher like the Beale ciphers. But Quicktrader on Morf’s forums was quick to point out the code’s resemblance to a Vigenère cipher matrix, due to the way the numbers repeat in an aligned pattern.

The matrix appears with a lot of other material, including handwriting samples, and this crossword puzzle:

Perhaps someone’s interest in puzzles aroused the suspicions of investigators.

Have a look at the new documents. Can you find anything interesting?

Forum user 4on4off had an interesting idea: Why not run the Gutenberg crib search program again, but against the Zodiac’s own writings instead of the massive collection of books in the Gutenberg collection?

I ran the search, and it found a few matches. Here are the files containing the results:

Results for the 408 cipher
Results for the 340 cipher

In each file, the matches resulting in the highest Zkdecrypto scores are displayed first. Here is a sample line from one of the files:

37, 237, +yBX1*:49CE>VUZ5-+|c.3zBK(Op^.fMqG2Rc, RSEENSIGNEDYOURSTRULEYHEPLUNGEDHIMSEL, 15, 1.8402534E-5, {0 17} {2 23} {20 29} {19 36} , 2952.125, 79.78716

And here’s an explanation of the data format:

  • 37: Length of chunk
  • 237: Position of chunk. Positions start at 0.
  • +yBX1*:49CE>VUZ5-+|c.3zBK(Op^.fMqG2Rc: Transcription of cipher text chunk
  • RSEENSIGNEDYOURSTRULEYHEPLUNGEDHIMSEL: Plain text chunk
  • 15: Number of unique letters in the plain text
  • 1.8402534E-5: Constraint difficulty. Lower values reflect higher difficulty (due to larger numbers of repeated symbols)
  • {0 17} {2 23} {20 29} {19 36}: Positions of repeated symbols, grouped into pairs
  • In the data for the 408, another value appears before the Zkdecrypto score, representing the proportion of characters in the solution that match the real known solution.
  • 2952.125: Zkdecrypto score
  • 79.78716: Zkdecrypto score divided by chunk length

What do you think? See anything interesting?

Harold Kravcik created a stir a few years back when he produced a solution to the 340-character cipher. Some people believed it to be the correct solution, so it was submitted to the FBI, and Harold required others to sign non-disclosure agreements to view his solution. This led to a lot of hype that the decades-old mystery of the 340 cipher had finally been solved. But eventually, confidence in his solution was lost. The drama resulting from all this caused Harold, and others who believed in the solution, to receive ridicule and derision from folks in the Zodiac community who are exhausted by the parade of discredited cipher solutions that have emerged since the Zodiac killer committed his awful crimes.

But what’s wrong with Harold’s solution?
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The program I wrote for the Project Gutenberg crib experiments also looked for pieces of text that fit into the entire 13-character cipher.


This cipher has many repeated symbols: One symbol repeats three times, and three other symbols repeat twice. Nevertheless, the program found over 2,700 unique bits of text that still fit “as is” into the the cipher text. Here are some interesting examples:
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Back in Part 1 we talked about the idea of using a large collection of books as a source of cribs to plug into cipher texts. Can we use a large collection of books, such as Project Gutenberg, to find pieces of real solutions to the ciphers?

I created an experiment to explore this idea. First, the 408 and 340 ciphers are broken down into chunks. Each chunk of cipher text must have some minimum number of repeated symbols. Chunks that have many repeated symbols are difficult to find solutions for, since the solutions must have repeated letters in the exact same locations. If we pick chunks that have too few repeated symbols, then there are way too many solutions that will fit.

Then, a program processes all of Project Gutenberg’s books. Each book is converted into a stream of uppercase text, with all punctuation and numbers removed. For example, here is what the beginning of A Tale of Two Cities looks like when it is converted:

ITWASTHEBESTOFTIMESITWASTHEWORSTOFTIMESITWASTHEAGEOFWISDOM
ITWASTHEAGEOFFOOLISHNESSITWASTHEEPOCHOFBELIEFITWASTHEEPOCH
OFINCREDULITYITWASTHESEASONOFLIGHTITWASTHESEASONOFDARKNESS

The program then looks through all of the text from the books to find pieces that fit into the chunks we created from the cipher texts. In total, the program examined over eleven billion characters of text.

It is a bit like finding a needle in a haystack, since the chances are low of finding a long piece of text that exactly matches the real solution. Actually, it’s a bit worse than finding a needle in a haystack: It is more like finding a needle in a needle stack, because very many pieces of text can fit into a chunk of cipher text. You have to come up with a way to figure out which needle is the one you’re really looking for.

For example, take a look at this 46-character chunk of cipher text from the 408-character cipher:
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Have you ever wanted to do cryptanalysis on someone’s back?

The latest tip jar doodle by a hot dog vendor in San Francisco shows a familiar figure with a brand new puzzle for you:

Can you solve it before your frank gets cold?

UPDATE: The tip jar doodle artist emerged, and posted the following background info on Morf’s Zodiac forum:
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In our many online discussions of the Zodiac’s ciphers, I’ve often needed to create pictures of symbols or pieces of the cipher text to illustrate a point. This became tedious after a while, so I created the “Zodiac Typewriter” to make this task simpler.

The Zodiac Typewriter gives you a quick way to string together a set of symbols to save as HTML (for blogposts and web pages), or as BBCode (for forum posts). It also generates hyperlinks so you can share your chunks of cipher text. This is so much faster than creating homemade, custom images. For example:

Here’s how to use it:

First, enter some text into the input box:

As you type your text, the generated cipher text image will appear below:

Each of the available cipher symbols is displayed in a table, along with the corresponding letter you can type to use it. The symbols come from the 408, 340, 13, and 32 character ciphers:

To use a symbol, enter its corresponding letter into the input box. Or, while your cursor is in the input box, click on one of the symbols. If you enter an unrecognized letter, a red question mark will appear.

If the table of symbols gets in your way, click the “hide” button.

Click the “lighter” button to make the cipher text gray. You can then click the “darker” button to make it black again. Maybe we’ll make this thing support more colors in the future.

When you’re happy with the cipher text, you can share it in several ways. One option is HTML, which is simply a collection of image tags that link directly to the images for each symbol. Click the “show html” button and you’ll see the HTML source. Copy and paste it to your blog post or web page and you’ll see the cipher text.

Another sharing option is to use BBCode for forum posts. Click the “show bbcode” button and you’ll see the bbcode necessary to reproduce your cipher text in a post. It is a collection of image tags, just like the HTML source. Simply copy and paste the BBCode into your post.

Finally, you can link directly to your cipher by clicking the “show links” button, which will generate hyperlinks for your cipher text. The “Full” link will open your cipher in the full Zodiac Typewriter interface. The “Compact” link opens a page that displays only your cipher.

!

Michael Cole has a great recent post on his site concerning the flood of web traffic again generated by the interest in Corey Starliper’s debunked claim of a solution to the 340-character cipher. Michael’s indictment of shoddy journalism is spot on.

If Corey Starliper walked into your office and announced that he had cured cancer, would you write the story: “Tewksbury Native: I’ve Cured Cancer” without seeking input from a medical professional? If he walked in and claimed to have solved one of math’s currently unsolved problems, would you write the article without doing something to evaluate the validity of his claim? I hope the answer to those questions is “No.” But, for some reason, if he walks in and says he’s solved a cipher that’s remained unsolved for the last 40 years, the Tewksbury Patch has no problem publishing an article without doing anything in terms of evaluating the probability that his solution is actually correct. His solution is garbage, pure and simple. Point me to one person with real cryptographic expertise who endorses Starliper’s solution. I’m going to go out on a limb and say that you cannot because I’m fairly certain one does not exist.

Those of us who have definitively shown Corey’s solution to be incorrect are often criticized for being “jealous” of him for solving the code, or for not having a solution that is better than his. What those critics fail to understand is that I would be among the first people to celebrate a real solution to any of the unsolved Zodiac ciphers, no matter who comes up with it! To be rid of another long-standing mystery would be a great relief to us all. In the meantime, there is no reason to sit back and accept unsubstantiated claims without evaluating their merit.

Cole’s article

This new Zodiac-related iPhone app was released recently by Rene Lowack:

Reveal the mysterious secret of the still unsolved encrypted Zodiac letter.

Zodiac was a serial killer active in California during the late 1960s and early 1970s. After killing, he wrote letters to local newspapers and demanded to publish them.
Some of them contained also encrypted messages. Only one of these cryptograms has been solved. The killer’s true identity is still unknown.

It’s time to reveal his secret now.

Features:
– Encrypted message 408 part 1 including solution
– Encrypted message 340 (still unsolved)
– Statistic view
– Current plaintext and substitutions
– Manual substitutions
– Randomized substitutions
– Background information

Screenshots: (more…)