Date & time (UTC/GMT):
October 3, 2021 5:00 PM
Many old encryption methods are still hard to break today. For instance, cryptanalyzing a short 19th century Playfair cipher is far from trivial. WW2 Enigma messages, spy ciphers from the Cold War, and manual methods used by criminals such as the Zodiac Killer can also be challenging, especially when the ciphertexts are short. On the other hand, techniques for breaking historical ciphers have recently made considerable progress. Computer-based cryptanalysis methods such as hill climbing and simulated annealing have been successfully applied to break original WWII Enigma messages, as well as one of the world's most famous unsolved codes, a 1970 ciphertext sent by the Zodiac Killer. The record in solving short Playfair messages has improved: whereas many years ago the shortest Playfair ciphertext that could be cracked required a minimum of 60 letters, now messages as short as 26 letters have been solved. However, many other historical ciphertexts are still unbroken to date. This presentation will introduce the most important historical ciphers, and modern techniques to break them.