Cryptology Dr. Richard Spillman Pacific Lutheran University
WW1 – The American Effort • Soon after the American declaration of war in April 1917, Herbert O. Yardley sold the war department on the idea of starting a cryptologic service called MI-8 • David Stevens, 32, an English instructor at UChicago • Thomas A. Knot, 37, an associate professor of English at UC • Charles H. Beeson, 47, associate professor of Latin at UC • Bliss Luquiens, 41, professor of Spanish at Yale • MI-8 became involved in many activities including • cryptography • secret inks • shorthand translation
Secret Inks • The Germans used several kinds of secret inks which could be developed by exposure to heat or by special chemicals • Allied chemists responded with a reagent that brought out secret writing of any kind because it could detect the fibers of paper which had been disturbed by a wetting action • Germans responded by writing in a sympathetic ink and then moistening the entire sheet • Allies responded with a chemical streak test that would detect whether the paper surface had been dampened - who but a spy would dampen paper? • Eventually, both sides discovered a general reagent that would detect any ink under any conditions • MI-8’s secret ink division, however, was testing over 2,000 letters a week and discovered 50 of major importance including the plans of one spy to import high explosives inside the hollow figures of saints and the Virgin Mary
Cryptographic Section • MI-8’s cryptographic section was very successful • One of their most important solutions involved the case of the only German spy condemned to death in the US during WWI. • Captured in January 1918 in Mexico by a US agent, he had a cipher letter • Broken by Dr. John Manly who went on to become one of the world’s leading authorities on Chaucer • After a marathon 3-day effort he broke down the 12 step transposition cipher:
The American Black Chamber • After Armistice, Yardley sold both the State Department and the War Department on jointly setting up a permanent cryptography organization • it became known as the American Black Chamber and was established on July 15, 1919 in NYC • its first task was to solve the codes of Japan and by 1921, they were regularly reading Japanese telegrams • In the summer of 1921, they solved telegram 813 of July 5th from the Japanese ambassador in London to Tokyo which contained instructions about the upcoming naval disarmament conference
Conference Results • Japan was demanding a tonnage ratio of 10 t0 7 with the US when the Black Chamber read what Yardley called the most important telegram he ever solved (0.5 represents 50,000 tons of ship - a battleship and a half) • “It is necessary to avoid any clash with Great Britain and America, particularly America, in regard to the armament limitation question. You will to the upmost maintain a middle attitude and redouble your efforts to carry out our policy. In case of inevitable necessity you will work to establish your second proposal of 10 to 6.5. If, in spite of your utmost efforts, it becomes necessary in view of the situation and in the interests of general policy to fall back on your proposal no. 3, you will endeavor to limit the power of concentration and maneuver of the Pacific and to make an adequate reservation which will make clear that this is our intention in agreeing to a 10 to 6 ratio.” • What do you think the Americans settled for with Japan?
The End of the Black Chamber • Between 1921 and 1929, the American Black Chamber solved more that 45,000 telegrams involving the codes of: • Argentina, Brazil, Chile, China, Cuba, England, France, Germany, Japan, Liberia, Mexico, Peru, USSR, Spain, ... • They even started on the codes used by the Vatican • It all ended on Oct 31, 1929 after Henry L. Stimson, Hoover’s Secretary of State received some solutions from the Black Chamber. He said “Gentlemen do not read each other’s mail”
Pre-WWII • After the American Black Chamber was dissolved, the Army decided to consolidate and enlarge its codemaking and codebreaking activities • It created the Signal Intelligence Service in 1930 with William Friedman as its chief. The Navy created OP-20-G to perform the same tasks • By 1936, both organizations had broken some of the Japanese codes and were sending the plaintext on to the War Department. By 1940 they sent daily reports. • The Director of Naval Intelligence, Read Admiral Walter Anderson code named these reports MAGIC
Traffic • There were so many messages being decoded that it was difficult to handle them all • They were divided: • Messages which originated in Tokyo on odd numbered days were handled by the Navy • Messages which originated in Tokyo on even numbered days were handled by the Army
Japanese Codes • The Japanese used several different but related ciphers • One cipher, called Oite by the Japanese and PA-K2 by the US involved 2 and 4 letter code groupings plus a special transposition • A typical 4 letter coded message might look like: • BYDH DOST JE YO IA OQ GU RA HY HY UQ VI LA YJ AY EC TY FI BANL This is written under a special key number: 10 15 11 16 2 8 1 5 17 3 7 13 19 4 18 6 12 9 14 B Y D H D O S T J E Y O I Q O Q G U R A H Y H Y U Q V I L A Y J A Y E C T Y Each line is then transcribed according to the numbers: SDEQTQ . . . The US could break it in 5 hours to 6 days (average 3 days)
Best Codes • Solutions to the J Code could take up to a month though sometimes they were found in a day or two • The Japanese sent their most secret messages using a rotor cipher system similar to ENIGMA called PURPLE • All but 2 or 3% of the PURPLE keys were recovered and most messages solved within hours by the US
Pearl Harbor – The Warning Signs • Warning Sign One: On December 1, the Navy confirmed that the Japanese fleet reassigned its 20,000 radio call signs at midnight, only 30 days after the last change (usual procedure was every 6 months) • Warning Sign Two: On December 3, Tokyo sent a PURPLE message to its Washington embassy. It was solved by SIS: • “...burn all codes but those now used with the machine and one copy each of 0 code (PA-K2) and abbreviating code . . . Stop at once using one code machine unit and destroy it completely . . .” • Under Sec. of State Wells say it as said, “...the chances had diminished from one in a thousand to one in a million that war could then be avoided.”
The Final Warning • Warning Sign Three: On December 7, at 1:28 am, a short message was received by the Navy’s radio station on Bainbridge Island and passed on to OP-20-GY in Washington, D.C. • The message was in PURPLE but it only took a few minutes to break because the key was a simple rearrangement of the December 1 key • The message was translated by 5 a.m. It read “Will the Ambassador please submit to the US Government our reply to the US at 1:00 pm on the 7th your time.”
The Japanese Reply • The reply, referred to in the Dec 7th message had been transmitted in 14 parts over the last 18.5 hours using PURPLE • The final sentence of the last part read: “The Japanese Government regrets to have to notify hereby the American Government that in view of the attitude of the American Government it cannot but consider that it is impossible to reach an agreement through further negotiations.” • This message was delivered to the White House, the Chief of Naval Operations, and the Secretary of the Navy one hour before the Japanese code clerks arrived at the embassy to decode it for their ambassador.
What Did We Know? • Intelligence had informed the US Government of three vital facts • the Japanese navy in an unusual move was trying to hide its position • the Japanese embassy in Washington was ordered to burn all codes • the Japanese Ambassador was instructed to deliver a message breaking off negotiations at exactly 1 p.m. on Dec 7th • What did it mean and why didn’t we react?
Midway • The battle for Midway illustrates the use of intelligence in the Pacific • The Japanese had so quickly overtaken the western Pacific, that they set their sights on forcing the US to defend and lose Midway - which they would use a base of operations for the final destruction of the US fleet • The one thing that stood between the US and the trap at Midway was the radio intelligence organization called the Combat Intelligence Unit, CIU, located at Pearl Harbor
The CIU • Three days after Pearl Harbor, the CIU was assigned the task of breaking the Japanese fleet cryptographic system called JN25 • Because of the enormous increase in radio traffic, the workload at CIU was impossible, so they found anyone they could to help, including the band of the USS California • JN25 was a two-part code of about 45,000 five digit groups enciphered by two volumes of 50,000 five digit additives • on December 1, 1941, a second edition of the code was created called JN25b - it took only four days to break most of this new code
Plans for Midway • By early May 1942, the US had recovered about 1/3 of JN25b and could read about 90% of the traffic • Hence, they could read most of Yamamoto’s plans to trap the US fleet at Midway • On May 20, 1942, Yamamoto issued the operations orders for the Midway assault. CIU also received the message and from its length could immediately tell its importance • 85 to 90% of it was broken within hours, it took a week to fill in most of the remaining holes • However, the important details were still in doubt: the dates, the times and the places. These were superenciphered in what appeared to be a polyalphabetic system which had only been seen 3 other times.
Best Intelligence • Naval intelligence applied ship speed and other data to estimate the date and time but the place information was more difficult • The Japanese indicated locations by maps with coordinates in code. • We found the coordinates AF in the text and thought that it meant Midway but no one was sure
The Trick • The chief of CIU worked up a trick to force the Japanese to give up the code for Midway • He asked Midway to send a clear message reporting that their fresh-water distillation plant had broken down • They sent the message and two days later CIU read a Japanese message reporting that AF was short of fresh water
The Result • On June 2, we caught the Japanese navy by surprise and sank 4 carriers - they never recovered • Adm. Nimitz later wrote: “Midway was essentially a victory of intelligence. In attempting surprise, the Japanese were themselves surprised.” • Gen. Marshall declared: “ (as a result of cryptanalysis) . . . We were able to concentrate our limited forces to meet their naval advance on Midway when otherwise we almost certainly would have been some 3,000 miles out of place.”
The Japanese Mistake • The Japanese had planned to change their fleet cryptographic system on April 1 to JN25c but they postponed it twice. First to May 1 and later to June 1. • When they finally changed the code on June 2, it blacked out CIU until August