[This is an adaptation of a presentation the NSA Historian made at the Solomon Kullback Memorial Conference at George Washington University on 25 May 1996.]
On April Fool's Day 1930, the U.S. Army began building its new Signals Intelligence Service (SIS), when William Friedman hired three"junior cryptanalysts." The first to report was Frank Rowlett, a young mathematics teacher from southern Virginia. He was followed by Abraham Sinkov of Brooklyn on April 10 and Solomon Kullback, also of Brooklyn, on April 21. For the better part of a decade, these gentlemen constituted the Army's sole effort against the codes and ciphers of potential enemies, and the nucleus of the Army communications intelligence (COMINT) service thereafter.
William Friedman is the subject of a published biography (The Man Who Broke PURPLE). Frank Rowlett has been profiled in recent books and articles about COMINT in World War II. Abraham Sinkov's "memoirs" were published in a recent issue of Cryptologic Quarterly. Solomon Kullback, however, remains a much lesser-known figure.
Solomon Kullback attended Boy's High School in Brooklyn, then City College of New York. His intention had been to teach, and he returned to Boy's High to do it, but soon found it not to his taste. Boys High was running three sessions daily and new instructors were put on the least popular shifts. He discovered his real interest was using math, not teaching it.
Fortuitously, at that time, he met an old friend from City College, Abraham Sinkov, who showed him a Civil Service flyer for"junior mathematicians" at $2,000 per year -- fairly good money in those days. Both took the examination, both passed, and both received letters from the U.S. Army Signal Corps, ordering them to report to Washington, DC as"junior cryptanalysts." Neither was certain what a cryptanalyst was, but both accepted with alacrity.
Upon arrival in Washington, Kullback found himself assigned to William F. Friedman. Friedman, now a civilian, had spent World War I working against German codes and ciphers and had nearly 10 years experience training military cryptologists; he now began an intensive program of training in cryptology for his new civilian employees.
Friedman encouraged his employees to further their education and also obtain commissions in the military reserves. Thus, for several summers running, the three SIS cryptanalysts attended training camps at Fort Meade until they received commissions as reserve officers in the Army. Kullback and Sinkov took Friedman's admonitions on education seriously and spent the next several years attending night classes; both received their doctorates in mathematics. Afterward, Kullback rediscovered a love of teaching; he began offering evening classes in math at George Washington University from 1939 on, and found a new pleasure in teaching.
Once they had completed the training Friedman expected of them -- nearly two years -- these three were put to the work for which they had actually been hired, compilations of cipher or code material for the U.S. Army. It was an odd business. The SIS had no machinery for code compilation, so the essential method to prepare a 50,000-word code was to draw up two sets of 3x5 cards -- the encryption side and decryption side -- and play"52 pickup." The cryptologists locked themselves in a vault, took handfuls of the encryption cards, and tossed them in the air, then followed this up with extensive and tedious cross-checking.
On one occasion, a major from another office discovered them tossing around handfuls of cards. He cautiously asked Friedman about it and received reassurances that it was a purposeful endeavor."I thought this code business had finally gotten to them," he said.
Another task was to test commercial cipher devices which vendors wished to sell to the U.S. government. Kullback recalled,"We solved them for our own amazement or amusement," but the exercise had practical consequences -- their skill kept the U.S. government from adopting insecure methods of encipherment. Furthermore, these three never found one they couldn't solve, and the work gave them considerable experience in the range of machine systems then available.
In the 1930s, the SIS concentrated on communications security (COMSEC), the protection of American communications. Occasional work against foreign messages was justified on the grounds that they were keeping informed on developments in order to strengthen America's systems. However, in 1936, SIS began to get regular intercepts of Japanese diplomatic communications. The Japanese, in the 1930s had begun converting to machine encipherment systems. The SIS gave the first Japanese machine they attempted a covername from the first color of the spectrum -- RED. With a solid background now in machine systems, Kullback commented in retrospect,"it wasn't very difficult really for us to work it out."
Kullback worked in partnership with Frank Rowlett against RED messages. Almost overnight, these two unravelled the keying system and then the machine pattern -- with nothing but the intercepted messages in hand. Using the talents of John Hurt, a talented linguist, to translate text, SIS started issuing current intelligence to military decision-makers./p>
It was an exceedingly critical time. The first RED messages gave U.S. officials inside information about the signing of the so-called Tripartite Agreement, in which Japan tied itself to Germany and Italy -- ostensibly against the Soviet Union, but, in actuality against the western Allies as well. The solution of RED began a long string of American successes against Japanese and other foreign high-level cryptographic systems.
In May 1942, five months after Pearl Harbor, now Major Kullback was sent to Great Britain to expedite these exchanges. Kullback learned how the British were producing COMINT of high quality by exploiting the famous ENIGMA machine. He also cooperated with the British in the solution of more conventional German codebook-based systems. After one was completed, he borrowed a catch-phrase from the then-popular comedian Red Skelton, and cabled back to the office,"We dood it!" Shortly after his return to the States Kullback moved into the Japanese section as its chief.
Even in the midst of war, Kullback demonstrated he was a"people person." For example, in order to boost morale, he often would come to work on the night shift to show the overnight workers they had not been forgotten. He also played a mean center field on the AHS baseball team.
Cryptology proved vital role to Allied victory. Kullback summed it up by saying,"Ultimately, we got into every bit of traffic…[T]here wasn't a damn thing that the Japanese transmitted that we weren't able to read… [M]ore than the translators could go through and really more than the intelligence people needed to maintain the battle order…"
After the war, the United States tried several methods of centralizing its cryptologic activities; eventually forming the National Security Agency in 1952. In this new world, the original SIS cryptanalysts assumed senior positions. Rowlett became chief of cryptanalysis, Sinkov of COMSEC, and Kullback of Research and Development (R&D).
The primary problem facing R&D in the post-war period was development of high-speed processing equipment. Kullback supervised a staff of about 60, including such innovative thinkers in ADP development as Leo Rosen and Sam Snyder. His staff pioneered new forms of input and memory, such as magnetic tape and drum memory, and compilers to make machines truly"multi-purpose." Perhaps based on his memories of"52 pickup," Kullback gave priority to using computers to generate COMSEC materials.
Solomon Kullback retired from NSA in 1962. As it happened, his retirement from government meant only the enlargement of his teaching career. He now focused directly on his teaching at George Washington University. His list of publications on statistics, already long, grew ever more extensive. With Solomon Kullback, almost all conversations ultimately had a way of reverting to the subject of mathematics, it was the great center of his life.
Solomon Kullback is remembered by his colleagues at NSA as straightforward; one described him as"totally guileless, you always knew where you stood with him." One former NSA senior recalled him as a man of unlimited energy and enthusiasm and a man whose judgment was usually"sound and right." He is also remembered as the man who usually took his bowling ball along on TDYs and spent his evenings practicing.
The original members of SIS were a unique quartet, men who ought to be national heroes. Their love was as much for the process as the result, the cryptanalysis as the intelligence derived from it, but what they did, the breakthroughs against the high-level code and cipher systems of our principal enemies, surely shortened the period of war by many months and resulted in the saving of thousands of American and British lives.
Years later, in an interview with NSA's oral historian, Solomon Kullback was modest about his accomplishments, but made a telling comment about his activities against German cryptography. He still recalled many of the details of these systems, described them in considerable detail, and commented:"They were a lot of fun."
Solomon Kullback passed away in 1994.
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