The Zodiac Killer Cipher

Posted by Jonas Elfström Fri, 25 May 2007 16:31:00 GMT

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.

Posted in Ruby, Cryptography | 5 comments

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    1. Avatar
      jonelf Wed, 30 May 2007 11:42:06 GMT
    2. Avatar
      NewGuy Thu, 01 Jan 2009 00:10:59 GMT

      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

    3. Avatar
      Jonas Elfström Thu, 23 Jun 2011 09:46:00 GMT
    4. Avatar
      Jonas Elfström Thu, 23 Jun 2011 09:49:12 GMT
    5. Avatar
      Jonas Elfström Fri, 19 Aug 2011 14:07:56 GMT

      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

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