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 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 ...

Vernam cipher Vernam is a surname. Notable people with the surname include: *Charles Vernam (born 1996), English professional footballer *Gilbert Vernam (1890–1960), invented an additive polyalphabetic stream cipher and later co-invented an automated one-time ...

encryption system developed by the UK during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

for use on

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 ...

circuits. During the 1950s, it was used by the UK and US for liaison on cryptanalysis. 5-UCO was fully synchronous, and therefore could be electrically regenerated on tandem high frequency (HF) radio links (i.e. one link connected to the next). It could operate directly with commercial circuits. The system also provided

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 ...

(TFS). Another feature of the 5-UCO was that the receiving operator could maintain synchronisation if the path delay suddenly changed by "walking up and down" the key tape (one character at a time or one bit at a time). This procedure avoided the cumbersome task of a restart.Melville Klein, "Securing Record Communications: The TSEC/KW-26", 2003, NSA brochure, p. 4
(PDF)
/ref> 5-UCO required large amounts of key tape to operate on a continual basis. In 1960, supplying the key tape for a single 5-UCO in continuous use cost £5000 per year ()."Awards to civilian personnel in respect of cypher machine development", 1955-1960, PRO AVIA 65/977 In the US, the logistical problems involved in the generation, supply and destruction of sufficient quantities of key tape limited its use to only the most sensitive traffic. The

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 ...

sought to develop 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. Colonel G. ff Bellairs was awarded sums totalling £2250 for the development of 5-UCO, £750 in 1943, and £1,500 in 1960. Dr G. Timms and Mr D. C. Harwood were also awarded £1,000 for work on random tape for 5-UCO.

References

External links

5-UCO on Crypto Museum website
*

Rockex Rockex, or Telekrypton, was an offline one-time tape Vernam cipher machine known to have been used by Britain and Canada from 1943. It was developed by Canadian electrical engineer Benjamin deForest Bayly, working during the war for British Secur ...

{{Cryptography navbox , machines Encryption devices

See also

References

External links