Alice, Bob, and Mallory: The Zodiac Killer Cipher

The Zodiac Killer Cipher

Jonas Elfström — Fri, 25 May 2007 18:31:00 +0200

The Zodiac Killer was a serial killer in the late sixties and maybe early seventies. He sent a number of letters to the press, including four ciphers or cryptograms and only one of them has been solved. The killer's identity remains unknown.

Chris McCarthy has a nice page about the cipher and he also has an ASCII version of the cipher.

Here's a small Ruby hack that calculates the character frequency using the ASCII version of the cipher. Feel free to use it if you like to have a go at cracking it!

EDIT: At this page you can have a go at cracking it real-time. I am not convinced it's really a homophonic substition cipher since the frequency analysis shows that the 340 does not have a flat frequency distribution.

It would be nice to know what cryptographic literature was available for the public in northern California in the late sixties.

"The Zodiac Killer Cipher" by Jonas Elfström

Fri, 19 Aug 2011 16:07:56 +0200

Corey Starliper claims to have solved the 340-character Zodiac Killer but it seems to be a hoax. http://oranchak.com/zodiac/corey/hoax.html

"The Zodiac Killer Cipher" by Jonas Elfström

Thu, 23 Jun 2011 11:49:12 +0200

Nice to see John Graham-Cumming having a go at it:

http://blog.jgc.org/2011/06/how-zodiac-enciphered-zodiac-408-cipher.html

http://blog.jgc.org/2011/06/identification-of-homophone-sequences.html

"The Zodiac Killer Cipher" by Jonas Elfström

Thu, 23 Jun 2011 11:46:00 +0200

I’m the guy who took 3 days off of work in an attempt to crack the Zodiac serial killer’s last remaining undeciphered message. - A quite confused and confusing try.

"The Zodiac Killer Cipher" by NewGuy

Thu, 01 Jan 2009 01:10:59 +0100

Hello,

It would be nice to know what cryptographic literature was available for the public in northern California in the late sixties.

I don’t want to seem like a smarta**, but it would have had to be something printed before or during the late 60s. The 408 was a simple substitution cipher. The 340 is most likely a substitution+transposition cipher. The number of permutations to test for this is enormous. I suggest testing in that area.

NewGuy

"The Zodiac Killer Cipher" by jonelf

Wed, 30 May 2007 13:42:06 +0200

Mono-, Bi and Trigram Frequency for English