5-UCO
Encyclopedia
The 5-UCO was an on-line one-time tape
Vernam cipher encryption system developed by the UK
during World War II
for use on teleprinter
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 (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.
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. 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 sought to develop a replacement, an effort later taken over by the newly-formed National Security Agency
and resulting in the fielding of the KW-26
(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.
One-time pad
In cryptography, the one-time pad is a type of encryption, which has been proven to be impossible to crack if used correctly. Each bit or character from the plaintext is encrypted by a modular addition with a bit or character from a secret random key of the same length as the plaintext, resulting...
Vernam cipher encryption system developed by the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
for use on teleprinter
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
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 (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.
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. 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 sought to develop a replacement, an effort later taken over by the newly-formed National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
and resulting in the fielding of the KW-26
KW-26
The TSEC/KW-26, code named ROMULUS, was an encryption system used by the U.S. Government and, later, by NATO countries. It was developed in the 1950s by the National Security Agency to secure fixed teleprinter circuits that operated 24 hours a day...
(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.