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The History Of NSA Computers, Up Until 1964. Part III.
Alex Trent
Staff Writer
2010-06-17
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Recently a formerly classified document was declassified describing how the NSA used computers to crack codes.
In Part II, we covered the ATLAS II, the second type of computer used by the NSA for code cracking. The next computer built, ABNER, was very different from its predecessors.
After the Pendergrass Report was published in December of 1946, the Army Security Agency made plans to acquire a computer similar to the Navy's proposed ATLAS. In 1948, ASA analysts visited the three major computer installations currently in existence. The analysts performed experiments using different programming order codes. They concluded that four-address logic (RAYDAC and EDVAC) was preferred over one-address logic (ATLAS and UNIVAC). The ability to use binary notation was found to be a necessary requirement (this disqualified UNIVAC).
The Reeves Instrument Corporation provided the design of ABNER. Mercury delay lines with access time between 48 and 348 microseconds were used to compose a 1024 word memory bank. Basic logic was based on the EDVAC design of 16 four-address instructions and 45-bit words.
ABNER's memory was based on the idea that electric pulses would be converted to an analog acoustic signal that could travel through tubes of mercury that used amplifiers at the opposite end to reconstruct the analog wave into an electrical signal. This digital to analog conversion and subsequent analog to digital conversion allowed the storage of data as the signals moving through the mercury could only move at the speed of sound, much slower than electrical signals. A tank of mercury was a glass tube around two feet long. Two cabinets containing 64 mercury delay lines each made up the memory bank. Each tube was held eight words of 48 bits at one-megacycle-per-second with the aforementioned delay time of 384 microseconds.
ASA engineers worked closely with programmers to build ABNER. This allowed the ASA to incorporate new feature improvements as ABNER was constructed. This was preferred rather than waiting for the next successor computer. Paired stream comparison, data stream manipulation, and character transformations as modular additions were a few of the logic features added. Besides the new logic features, ABNER, had several input-output features including: a console with status lights, an input-output typewriter, a data conversion unit, punched card and punched paper-tape readers and punches, and it could utilized up to six magnetic tape drives.
The construction of ABNER took about two years. The first ABNER was delivered in 1951, followed by a second ABNER in 1955 using quartz instead of mercury for its memory banks. NSA engineers also constructed an clone of of ABNER's logical design, but with parallel circuits called BAKER. BAKER was a slow-speed analog of ABNER, based on the design of ATLAS I. Unfortunately, BAKER was never reliable enough to really use in training or debugging, but BAKER was a great achievement. It is thought however, that BAKER's use of parallel circuits to simulate a powerful serial computer should not have been attempted.
Next time, we'll cover more NSA computers of the past, the successors to ABNER and BAKER.
For more in depth reading see: http://www.governmentattic.org/3docs/NSA-HGPEDC_1964.pdf.
View All Articles by Alex Trent
About the Author:
Alex is a staff writer for SecurityProNews.
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