SUNY Geneseo Department of Mathematics
Monday, October 4
INTD 105 17
Fall 2021
Prof. Doug Baldwin
(No.)
Final versions of the race essays are due to me by this evening.
Also don’t forget that I want to meet with you to discuss those final versions. The same is true of the final versions of the warm-up essays; many of you still need to have those meetings.
Friday we worked on breaking some messages I encrypted using a substitution cipher:
XCEQFBOPA BD LJA ZHTFLJ SBDLAF HZ LJA SCF: C PJHUL LHSD (FHQAFL JCFFBU)
ZHF LJHTUCDOU HZ NACFU, KBDPU, ITAADU, CDO PADAFCWU JCYA FAWBAO HD AZZBXBADL XHEETDBXCLBHD BD HFOAF LH PHYAFD LJABF XHTDLFBAU CDO XHEECDO LJABF CFEBAU. CL LJA UCEA LBEA, LJAN JCYA CWW QAAD CSCFA HZ LJA XHDUAITADXAU HZ LJABF EAUUCPAU ZCWWBDP BDLH LJA SFHDP JCDOU, ... (UBEHD UBDPJ)
LJA UHWTLBHD BU QN DH EACDU UH OBZZBXTWL CU NHT EBPJL QA WACO LH BECPBDA ZFHE LJA ZBFUL JCULN BDUVAXLBHD HZ LJA XJCFCXLAFU (AOPCF CWWCD VHA)
At the end of Friday’s class we started working as a group to break the longest of these messages. When the class period ended we had decided…
We had also decided to continue building on these clues today. We did so, using the “Black Chamber” substitution cracking tool.
After putting in the letter equivalences for “A,”, “L,” and “J,” the decryption still looked at least plausible. We guessed a few more letters based on them making plausible words; this worked particularly well when guessing groups of letters. In the course of doing that, we guessed that ciphertext “B” corresponds to plaintext “I,” which means that ciphertext “C” must be “A” (since “C” could be either “A” or “I”). At about this point we started to recognize words that had only 1 or 2 unknown letters in them. Filling in those letters led to more such words, and we broke the rest of the message straightforwardly. The final decryption (without punctuation, since the substitution tool leaves it out) reads:
FOR THOUSANDS OF YEARS KINGS QUEENS AND GENERALS HAVE RELIED ON EFFICIENT COMMUNICATION IN ORDER TO GOVERN THEIR COUNTRIES AND COMMAND THEIR ARMIES AT THE SAME TIME THEY HAVE ALL BEEN AWARE OF THE CONSEQUENCES OF THEIR MESSAGES FALLING INTO THE WRONG HANDS SIMON SINGH
Based on the first 2 chapters, what’s going on and who’s doing it?
The story is set during World War 2.
Tom Jericho is a government worker with PTSD and secrets. He works and studies at Cambridge University, as well working for the government. A talented mathematician, and student of Alan Turing’s at Cambridge.
Alan Turing appears only as background in this story, but he was a very important person historically (who we’ll study in depth when we read “Breaking the Code”). He was a key player in breaking Germany’s Enigma code, an inventor of the computer, and proposer of the Turing test. He was also gay, and forced to take drug treatments to suppress homosexuality in the 1950s, probably leading to his suicide in 1954.
Some of the actual history this story is set against…
Britain, being an island, relied heavily on imported raw materials and food to keep the war effort going, leading to the Battle of the Atlantic: Germany’s effort to cut off Britain’s supply chain by launching U-boat (i.e., submarine) attacks against the ships delivering goods to Britain.
German commanders in Europe kept in touch with U-boats in the Atlantic using the Enigma machine, i.e., a machine that performed very secure encryption and decryption. Breaking the Enigma code was thus crucial to Britain in being able to predict where U-boat attacks would happen. Capturing Enigma machines, especially U-boat ones, was an important part of this effort; even more important was capturing the code books that told U-boat crews what keys to use in the communication.
Finish discussing the background (both actual and in the novel) to Enigma.
Finish reading chapters 1 and 2 if you haven’t already.