What is Zodiac’s 340-character cipher?

Earlier this month I gave a talk about Zodiac’s unsolved 340-character cipher at the annual convention of the American Cryptogram Association in Hendersonville, NC. It is full of things I’ve learned over the years about the cipher. My goal was to try to summarize all the interesting “clues” in the cipher, and hopefully get more people interested in trying to solve it. Here is a video I made of the talk, including updated visuals:

It gets rather technical at times but that’s because the audience is full of fellow codebreaking enthusiasts.

The other talks at the convention were fascinating and covered a wide variety of topics, such as ancient Latin manuscripts, playing card ciphers, competitive codebreaking for kids, an NSA case study involving dictionary codes, cryptocurrencies, a code on William Friedman’s tombstone, puzzles as on-stage entertainment, and interrupted key ciphers. To top it off, the keynote talk was by Will Shortz, the famous New York Times crossword editor, in which he gave many interesting examples of devious crossword puzzles that contained hidden messages beyond the normal solutions.

There were so many intelligent and friendly codebreaking enthusiasts at the convention, and I hope some of them will turn their efforts to working towards a solution to Zodiac’s 340 cipher!