This experiment didn’t yield anything looking like a solution, so we tested all pairs of transpositions. Using AZdecrypt, we tested all row–major, column–major, alternating row–column, alternating column–row, inward spirals, outward spirals, diagonals and proper one-dimensional and two-dimensional decimation transpositions. Just for fun, I decided to plot this transposition using Mathematica: Perhaps solving the Z340 is a case of finding by trial and error the correct transposition, then using AZdecrypt to solve the homophonic substitution cipher.ĭavid outlined one particular transposition, which was discovered independently and posted to by user “daikon” and Jarl van Eycke (the author of AZdecrypt): the “ period-19,” which had some interesting statistical properties that would suggest that they were closer to the correct transposition. However, AZdecrypt cannot be used to solve the Z340 because when you run it on the Z340, it does not produce a solution. Experiments suggest that AZdecrypt can solve all homophonic substitution ciphers of the same length and symbol distribution as the Z340. Highly efficient programs for solving homophonic substitution ciphers exist, the best of which is AZdecrypt. In his presentation, David explored the idea that the cipher is both a homophonic substitution cipher and a transposition cipher. This cipher is considered one of the holy grails of cryptography, as at the time the cipher had resisted attacks for 50 years, so any attempts to find a solution were truly a moonshot. I was inspired by a YouTube video by David Oranchak, which looked at the Zodiac Killer’s 340-character cipher (Z340), which is pictured below. This gave me lots of time to look into interesting problems I’d been putting off for years. The wearing of masks was mandatory and we were limited to one hour a day of outside activity. In 2020, Melbourne, Australia, had a 112-day lockdown of the entire city to help stop the spread of COVID-19. The killer sent the fourth and final cipher (discussed in this blog post) to the San Francisco Chronicle after the 408-character cryptogram, deciphered in 1969, did not reveal the killer’s identity. The killer claimed that this cryptogram would reveal his identity when deciphered. He also included three ciphers, each containing one-third of a 408-character cryptogram. In these letters, the killer took responsibility for the crimes and threatened to commit further murders. Editor’s note: The Zodiac Killer (an unidentified American serial killer active during the 1960s and 70s) sent numerous taunting letters to the press in the San Francisco area with regard to a local murder spree.
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