FBI analysis from Dan Olson

From Zodiac Killer Ciphers Wiki
Jump to: navigation, search

This is a letter that FBI cryptanalyst Dan Olson sent to Tom Voigt:

"We havent seen any recent solutions or ideas that have generated a second look as of yet. If you can point us in the right direction we'll be all over it. FYI, if we ever do see a good partial or full solution we will forward it with our endorsement to the cold case squad at SFPD, but we will give credit to where credit is due.

I dont have a graphic to share but here are more details you can post instead: Statistics for repeated characters for each line of text show a distinct higher randomness with the lines we've discussed (1-3 and 11-13). The higher randomness may be due in part or whole to greater care by the writer to not repeat characters on these lines. This indicates homophonic substitution. The opposite is true for lines 4, 10, 14, 17 and 18, these lines have many repeats. Additionally, there is far greater randomness for rows versus columns. This rules out any form of columnar or diagnal transpositions (a big step forward).

These same statistical tests were done on Z408. The results suggest that 340 is similar to 408 except for the bogus rows: overall randomness of 408 is .48, 340 is .50. Row randomness of 408 is .22, 340 is .19. Column randomness of 408 is .48, 340 is .68. By way of comparison, row and column randomness should be near identical if the 340 does not contain any message, or if there is a message that is evenly scrambled."

My name is Dan Olson. I am the Unit Chief of the Cryptanalysis and Racketeering Records Unit that was featured on MysteryQuest episode. I wanted to pass to you the reasons behind the Z340 theories I presented on the episode last night. I believe these are important discoveries that may assist skilled codebreakers find a solution.

  • Statistical tests indicate a higher level of randomness by row, than by column. This indicates that the cipher is written horizontally and rules out any transposition patterns that are not strictly horizontal.
  • Lines 1-3 and 11-13 contain a distinct higher level of randomness than lines 4-6 and 14-16. This appears to be intentional and indicates that lines 1-3 and 11-13 contain valid ciphertext whereas lines 4-6 and 14-16 may be fake.
  • Because of the vertical symmetry of the statistical observations, the message may have been written, then split into two equal size parts and placed top over bottom.

Please feel free to disseminate these observations as you see fit. I ask that you please do not distribute my Email address beyond yourself. We share a desire to someday see the Z340 cipher solved, and more importantly, to identify the true killer and close this terrible chapter of history. Thanks.

Daniel Olson Unit Chief Cryptanalysis & Racketeering Records Unit FBI Laboratory