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:


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:

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:

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.

– 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…)

In Part 1, we looked out how to use Project Gutenberg‘s large collection of about 39,000 digitized books to apply cribs to cipher texts to try to tease out solutions. Another way we can use the collection of books is to see if any of the unique words and phrases used by the killer in his many correspondences can be found among the books. Did the killer use a unique writing style that was similar to the style of another author? Did he use relatively rare words that can only be found in a few sources? Can any of his many misspelled words be found in common usage by other authors, suggesting a connection? (more…)

One way to attack a substitution cipher is to guess what part of the plain text solution might be, “plugging” it into where you think it might fit in the cipher text, and then seeing if you can get more of the solution to appear in the rest of the cipher text. Known as a “crib“, this type of attack can be useful if you get lucky and pick the right text.

Donald Harden
Donald Harden, along with his wife, solved the 408-character cipher within a week after seeing it. (Image courtesy of

With skill and determination, Donald Harden and his wife got lucky. Their intuition that the killer used the words “I” and “killing” in the plaintext solution, combined with the fact that “L” is the most commonly doubled letter in English, led to their success in solving the first cryptogram sent by the Zodiac killer.

partially solved 408 cipher
Even with only the small phrase “I LIKE KILLING” used as a crib, other easily solved pieces pop out of the puzzle.
Hardens crack the Zodiac code

Fast forward over forty years. Luck continues to elude codebreakers who are still trying to unlock the remaining mysteries. Our tools have gotten faster and more sophisticated. There are still no definitive solutions to the remaining cryptograms, but we can use new tools to try out new ideas. (more…)

Retired Vallejo officer Lyndon Lafferty has been getting a lot of attention for his book in which he claims to know who the Zodiac killer was. The numerous criticisms of his claims aren’t mentioned by the various news stories, but you can find them here, here, here, here, here, and here.

Lafferty claims to have solved the unsolved Zodiac ciphers, but fails to provide details on his solutions. Like many of his other claims, he expects you to take his word for it. To make matters worse, instead of sharing the solutions outright, he says he intends to profit from them:

The detailed explanation and analysis, including the unbelieveable and undeniable pattern, will be offered for sale at the first opportunity.

Would you pay him?

Over forty years of frustration have passed since the Zodiac killer first sent his mysterious 340-character cipher to the San Francisco Chronicle. It only took a week for two teachers to solve his previous cipher. But many thousands of people, over four decades, have tried to crack the mystery of the 340-character cipher, to no avail. You may have seen many would-be solutions in news stories and on the internet. The 408-character cipher was solved with a definitiveness that defies any possible doubt, because it is impossible for the Harden’s key (Part 1, Part 2, Part 3) to produce such an easily understood plain text message purely by chance. No such solution yet exists for the 340, despite numerous claims to the contrary.

So, with so much failure and defeat confronting us, should we just accept the possibility that the killer, frustrated by the swift unlocking of his previous secret message, simply created a fake cipher to keep us all busy all these years?