SIGTOT was a
one-time tape
In cryptography, the one-time pad (OTP) is an encryption technique that cannot be cracked, but requires the use of a single-use pre-shared key that is not smaller than the message being sent. In this technique, a plaintext is paired with a rand ...
machine for encrypting
teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
communication that was used by the United States during World War II and after for the most sensitive message traffic. It was developed after security flaws were discovered in an earlier
rotor machine
In cryptography, a rotor machine is an electro-mechanical stream cipher device used for encrypting and decrypting messages. Rotor machines were the cryptographic state-of-the-art for much of the 20th century; they were in widespread use in the 19 ...
for the same purpose, called
SIGCUM
SIGCUM, also known as Converter M-228, was a rotor cipher machine used to encrypt teleprinter traffic by the United States Army. Hastily designed by William Friedman and Frank Rowlett, the system was put into service in January 1943 before any ...
. SIGTOT was designed by
Leo Rosen
Leo Rosen was a U.S. cryptanalyst who worked with Frank Rowlett at Signals Intelligence Service (S.I.S.) before the start of World War II on Japanese ciphers. Rowlett found a method to read the messages enciphered on the Japanese PURPLE machine ...
and used the same Bell Telephone 132B2 mixer as SIGCUM. The British developed a similar machine called the
5-UCO The 5-UCO (5-Unit Controlled)Ralph Erskine, "The 1944 Naval BRUSA Agreement and its Aftermath", ''Cryptologia'' 30(1), January 2006 pp14–15 was an on-line one-time tape Vernam cipher encryption system developed by the UK during World War II f ...
. Later an improved mixer, the SSM-33, replaced the 131B2,
SSM-33 (SIGTOT) Cryptosystem
/ref>
The phenomenon, codenamed TEMPEST
Tempest is a synonym for a storm.
'' The Tempest'' is a play by William Shakespeare.
Tempest or The Tempest may also refer to:
Arts and entertainment Films
* ''The Tempest'' (1908 film), a British silent film
* ''The Tempest'' (1911 film), a ...
, of sensitive information leaking by way of unintended electromagnetic radiation for the circuits used inside encryption machine was first discovered coming from the 131B2 mixers used in SIGTOT.[A History of U.S. Communications Security; the David G. Boak Lectures]
National Security Agency (NSA), Volumes I, 1973, Volumes II 1981, partially released 2008, additional portions declassified October 14, 2015
SIGTOT required large amounts of key tape to operate on a continual basis, which was needed for traffic flow security
Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication, it can be performed even when the messages are encrypted. In general, the greater the number of messages observed ...
. In 1955, NSA produced some 1,660,000 rolls of one time tape.Army Security Agency
The United States Army Security Agency (ASA) was the United States Army's signals intelligence branch from 1945 to 1976. The Latin motto of the Army Security Agency was ''Semper Vigiles'' (Vigilant Always), which echoes the declaration, often ...
began developing a replacement, an effort later taken over by the newly formed National Security Agency
The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collecti ...
and resulting in the fielding of the KW-26
The TSEC/KW-26, code named ROMULUS, (in 1966 the machine based encryption system was not code-named "Romulus," rather the code-name was "Orion," at least in the US Army's variant) was an encryption system used by the U.S. Government and, later, ...
(ROMULUS) system.[Melville Klein, "Securing Record Communications: The TSEC/KW-26", 2003, NSA brochure, p. 4]
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References
History of cryptography
Encryption devices
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