|Dr. Abraham Sinkov
(1907-1998) was a US cryptanalyst.
Sinkov, the son of immigrants from Russia, was born in Philadelphia,
but grew up in Brooklyn. After graduating from Boys High School --
what today would be called a "magnet school" -- he took his B.S. in
mathematics from City College of New York. (By coincidence, one of his
close friends at Boys High and CCNY was Solomon Kullback). Mr. Sinkov
taught in New York City schools but was unhappy with the working
conditions and anxious to use his mathematics knowledge in practical
The opportunity for a career change came in 1930. Sinkov and Kullback
took the Civil Service examination and placed high. Both received
mysterious letters from Washington asking about their knowledge of
foreign languages. Sinkov knew French and Kullback, Spanish. This was
acceptable to their prospective employer, and they were offered
positions as junior cryptanalysts. Although neither was quite certain
what a cryptanalyst did, they accepted.
The small Signals Intelligence Service (SIS) organization (Sinkov and
Kullback were the third and fourth employees there) had the primary
mission of compiling codes and ciphers for use by the U.S. Army. Its
secondary task was to attempt to solve selected foreign codes and
ciphers -- this was not necessarily done for intelligence purposes but
to keep the cryptanalysts abreast of new developments in the field.
William Friedman put his new employees through a rigorous course of
study of his own design in cryptology, bringing them to high levels of
skill in making and breaking codes and ciphers. Friedman also
encouraged other self-improvement endeavors: his employees trained
summers at a camp at Ft. Meade to earn commissions in the military
reserves. Both Sinkov and Kullback also went on to receive doctorates
in mathematics. Sinkov received his in mathematics in 1933 from The
George Washington University.
SIS grew slowly throughout the early 1930s. However, successes against
Japanese diplomatic machine systems after 1935 provided the U.S.
government with critical information during a series of crises. This
success had practical consequences for SIS, as well. For the first
time, SIS began to garner respect from its military superiors. Once
the military understood that this small organization could read
sensitive messages from a potential adversary, the Signal Corps
increased the SIS budget and authorized increased hiring of
In 1940, even though the United States was not officially a combatant,
the U.S. and Britain initiated exchanges of technical material.
Included in this was a cautious sharing of cryptologic information:
the British in stages revealed the extent of their considerable
success against high-level German systems, the U.S. its equivalent
success against Japanese. This led to an unprecedented level of
cooperation in COMINT between the two countries during the war,
resulting in more personnel, bigger budgets, and a wider range of
activities for the organization. In 1936, Dr. Sinkov was assigned to
the Panama Canal Zone, where he established the U.S. Army's first
permanent intercept site outside the continental United States.
In January 1941, while Britain battled Nazi Germany but nearly a year
before the United States entered the Second World War, Captain Sinkov
was selected as a member of a delegation to the United Kingdom for
initial sharing of information about the two countries' respective
cryptologic programs. The delegation returned in April with mixed
results to report. Sinkov and his colleagues had been shown Bletchley
Park, the secret headquarters for British cryptology, and exchanged
information on German and Japanese systems. It is still unclear how
much the American delegation was told about British success against
the German Enigma machine, but Sinkov later recalled that they were
told about the Enigma problem only a short while before the delegation
was to leave, and that details were sketchy. Nevertheless, the mission
to the UK was a success overall and helped give US-UK cryptologic
relations a strong practical foundation.
After the Japanese attack on Pearl Harbor on December 7, 1941, the
Japanese also attacked the Philippine Islands. General Douglas
MacArthur had been ordered to leave the Philippines and re-establish
U.S. Army headquarters in Australia, from whence counterattacks might
be launched. MacArthur recognized the need for cryptologic support,
thus, on 15 April 1942, he established the Central Bureau (CBB),
cobbling it together from refugee elements of American cryptologists
evacuated from the Philippines, Australian cryptologists, and other
Allied contingents. CBB began in Melbourne, then moved to Brisbane.
In July 1942, by now Major Sinkov arrived in Melbourne as commander of
the American detachment at Central Bureau. The Director of CBB on
paper was General Spencer B. Akin, MacArthur's chief signal officer,
but General Akin in practice seldom visited the organization. He had
worked with Sinkov in Washington and in Panama, and confidently left
CBB operations under his control.
Dr. Sinkov, who demonstrated strong organizational and leadership
qualities in addition to his mathematics skills, brought this group of
Americans and Australians -- representing also different military
services from their countries -- into a cohesive unit. CBB quickly
became a trusted producer of Signals Intelligence (SIGINT) for
MacArthur and his senior commanders. This SIGINT enabled consistent
success in the air war against the Japanese and allowed MacArthur to
win some stunning victories in the ground campaign in New Guinea and
After the war, Sinkov rejoined SIS, now renamed the Army Security
Agency, and, in 1949, when the Armed Forces Security Agency (AFSA) --
the first centralized cryptologic organization in the United States --
was formed, Sinkov became chief of the Communications Security
program. He remained in this position as AFSA made the transition into
the National Security Agency.
In 1954, Dr. Sinkov became the second NSA official to attend the
National War College (the first was Dr. Louis Tordella). Upon his
return, he became Deputy Director for Production, effectively swapping
jobs with his old colleague Frank Rowlett. Dr. Sinkov retired from NSA
In 1966, he wrote Elementary Cryptanalysis: A Mathematical Approach.
Published by the Mathematical Association of America, it was one of
the first books on the subject available to the general public.
Dr. Abraham Sinkov lived in retirement in Arizona after two careers,
32 years in NSA (and its predecessors), followed by an appointment as
a professor of mathematics at Arizona State University.
Hall of fame
Colonel Sinkov is a member of the Military Intelligence Hall of Fame.
Sinkov, Abraham. Elementary cryptanalysis :a mathematical approach,
Mathematical Association of America, Washington, D.C. ISBN