Homophonic Substitution Cipher: Cracking the Code of a Killer

Robert Stone began the presentation by demonstrating the mechanics of a substitution cipher. He walked through the details carefully and in detail, making certain that everyone understands the mechanics. From there, he moves forward to discuss the vulnerabilities of the basic subbstitution cipher.

Next, Robert moves into the homophonic substitution cipher and how it reduces the weaknesses of the standard substitution cipher. He worked through an example to show how the system works. The group spent quite a bit of time discussing the implications of these changes.

Finally, Robert went on to describe the circumstances of the three letters that the Zodiac killer sent to different newspapers. He described the letters and what the killer sent with them. He, then, walked through the exercise of attempting to crack the cipher, following in the footsteps of those who solved the cipher.

Unlike many technical talks, this one covered technical details, theory, and real life. The lively conversation during and after the presentation showed how it was enjoyed.

The presentation is available on-line.

We had 10 people attending this month. As always, we'd like to thank HostGator, LLC for providing the meeting space and food for the group.