Zodiac Killer: Code-breakers solve San Francisco killer's cipher

See <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=25390941" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=25390941</a> for earlier discussion.

Breaking ciphers was one of my hobbies growing up the 60&#x27;s. I wasn&#x27;t particularly good at it, but I understood the methods used--I read everything I could find on the subject that was available in the open literature. See the bibliography below if you&#x27;d like to try some interesting cryptography on paper and pencil methods.<p>In graduate school I studied CS and I proposed to my Ph.D. advisor that I would like to do research into cryptography (this was 1983) and he told me that all the interesting things about cryptography have already been discovered and that I should work on something else.<p>In 1983 Byte magazine, volume 3, an article proposed using a program based on the <i>Bazeries Cylinder</i>, see [6, 7], to obtain a practically unbreakable cipher. I didn&#x27;t own a personal computer at the time, so as soon as I could get together with my best friend, a fellow grad student that owned a PC, we were able to break the cipher in just one evening. (Unfortunately, we were the second to do so and missing out on the $10 prize for the first person that broke the cipher.)<p>There are paper and pencil ciphers that are well designed and are much stronger than the Zodiac Killer&#x27;s ciphers as I understand them. One designed for Soviet spies, known as the VIC cipher, resisted US cryptographers (as far as I know) and is explained in an interesting Scientific American in the July 1966 edition, see [7]. See also [8].<p>* Pre-computer age cryptography<p>[1] Helen Fouché Gaines, Cryptanalysis, <a href="https:&#x2F;&#x2F;archive.org&#x2F;details&#x2F;cryptanalysis00hele" rel="nofollow">https:&#x2F;&#x2F;archive.org&#x2F;details&#x2F;cryptanalysis00hele</a><p>[2] William F. Friedman, Riverbank Publications, <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Riverbank_Publications" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Riverbank_Publications</a><p>[3] William F. Friedman, The Friedman Lectures on Cryptography, <a href="https:&#x2F;&#x2F;www.nsa.gov&#x2F;Portals&#x2F;70&#x2F;documents&#x2F;news-features&#x2F;declassified-documents&#x2F;friedman-documents&#x2F;publications&#x2F;ACC15281&#x2F;41785109082412.pdf" rel="nofollow">https:&#x2F;&#x2F;www.nsa.gov&#x2F;Portals&#x2F;70&#x2F;documents&#x2F;news-features&#x2F;decla...</a><p>* Interesting historical information, there are so many to choose from now but two of my favorites (one old and one more recent)<p>[4] David Kahn, The Code Breakers, <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;The_Codebreakers" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;The_Codebreakers</a><p>[5] Leo Marks, Between Silk and Cyanide: a Codemaker&#x27;s Story 1941-1945 (this is less about cryptography and more about the practical problems of secret code and ciphers during WWII).<p>* The Thomas Jefferson wheel cipher or Bazeries Cylinder<p>[6] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Jefferson_disk" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Jefferson_disk</a><p>[7] <a href="https:&#x2F;&#x2F;archive.org&#x2F;details&#x2F;eu_BYTE-1983-03_OCR&#x2F;page&#x2F;n3&#x2F;mode&#x2F;2up?q=Bazeries" rel="nofollow">https:&#x2F;&#x2F;archive.org&#x2F;details&#x2F;eu_BYTE-1983-03_OCR&#x2F;page&#x2F;n3&#x2F;mode...</a><p>* The (once) unbreakable VIC cipher<p>[7] David Kahn, Sci American, Vol 215, No 1 (July 1966), pp 38--47.<p>[8] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;VIC_cipher" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;VIC_cipher</a>

Very cool how they went through their steps etc in the video on Youtube. Lots of intelligence and hard work on show there.<p>So part of me is excited &#x2F; impressed &#x2F; happy for them. Serious effort and seriously impressive. Especially catching Zodiac&#x27;s mistake and adjusting for it to completely solve the cipher.<p>They other part of me hates that someone so terrible has been able to capture the imaginations of people for so long with his terrible games.

video shows just a weird positioning of letters, like that&#x27;s how zodiac had put them into cypher (one down, three to the left). It seems to me that originally text was written in some geometric shape, mostly from top to bottom, then was copied to the paper from left to right. This could explain &quot;mistakes&quot;, &quot;life is&quot; part written horizontally etc. I wonder, what the shape was.

Is the argument that this is a simple procedure which yields recognizable English text? In other words, how does one confirm that this was indeed the encryption procedure originally used?<p>I ask because there are similar procedures one can apply to other documents, but they have been dismissed as coincidental. Bible codes are the example which immediately come to mind.

I think the Zodiac killer must have wanted this to be broken at some point, maybe they overestimated the difficulty though. It&#x27;s not hard to make an unbreakable cipher (one time pad, or just doing a large number of transformations), seems like using a fairly simple method was an intentional choice. Or maybe they are just insane, but it doesn&#x27;t make sense to me that you would actually try and securely encrypt something and then submit it to the public, if there is no target audience you might as well just send random characters.

Looks like obscurity <i>is</i> security worked for 50 years!

TLDR:<p>HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME THAT WASNT ME ON THE TV SHOW WHICH BRINGS UP A POINT ABOUT ME I AM NOT AFRAID OF THE GAS CHAMBER BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE SO THEY ARE AFRAID OF DEATH I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE WILL BE AN EASY ONE IN PARADICE DEATH IS LIFE

Misspellings would probably be in the authors corpus otherwise: somebody should see &quot;paradice&quot; and go hmmmmm

Why is the message in the video much longer, including a part such as that wasn&#x27;t me on the tv show, etc, but not in the text of the article?

&gt; IN PARADICE DEATH<p>Remember: reading the deciphered ramblings of a deranged psychopath is obviously going to have misspellings and weird idiosyncratic oddities in them.<p>My take is (if the killer was in any way rational) is that she knew the plaintext would be unraveled at some stage. If not by quantum computers, then a team of dedicated sleuths who know how to program. So yes: the misspellings could be deliberate.

yet another unsolved problem solved with the aid of a computer. I do not think it would have been possible to solve it without a computer unless you were lucky enough to guess the rule

It seems like this is a rather simple cipher. Is it? I find it very surprising it took this long.

Wow, all that work and it was just some dumb nonsense (or maybe another cipher disguised as nonsense).

I am probably being naive; but because the Zodiac uses multiple ciphers and eventually a very complex and detailed one, couldn’t we infer he was probably either a computer science or math major?<p>Clearly this should have been able to filter out potentials suspects and reduce the pool of possible suspects? Just a run of the mill person is not gonna come up with these codes right?