Editing Lorenz cipher (section)

===Decryption machines===
Several complex machines were built by the British to aid the attack on Tunny. The first was the [[British Tunny]].<ref>{{Harvnb|Halton|1993}}</ref><ref>[https://www.theregister.co.uk/2011/05/26/bletchley_park_tunny_rebuild_project/ Bletchley Park completes epic Tunny machine] The Register,  [https://www.theregister.co.uk/2011/05/26/ 26 May 2011], Accessed May 2011</ref> This machine was designed by Bletchley Park, based on the [[reverse engineering]] work done by Tiltman's team in the Testery, to emulate the Lorenz Cipher Machine. When the pin wheel settings were found by the Testery, the Tunny machine was set up and run so that the messages could be printed.

A family of machines known as "[[Heath Robinson (codebreaking machine)|Robinsons]]" were built for the Newmanry. These used two [[paper tape]]s, along with logic circuitry, to find the settings of the ''χ'' pin wheels of the Lorenz machine.{{sfn|Copeland|2006|p=66|loc="Machine against Machine"}} The Robinsons had major problems keeping the two paper tapes synchronized and were relatively slow, reading only 2,000 characters per second.
[[File:ColossusRebuild 11.jpg|thumb|A team led by [[Anthony Sale|Tony Sale]] (right) reconstructed a Colossus (Mark II) at Bletchley Park. Here, in 2006, Sale supervises the breaking of an enciphered message with the completed machine.]]
The most important machine was the [[Colossus computer|Colossus]] of which ten were in use by the war's end, the first becoming operational in December 1943. Although not fully programmable, they were far more efficient than their predecessors, representing advances in electronic digital [[computer]]s. The [[Colossus computer|Colossus]] computers were developed and built by [[Tommy Flowers]], of the [[Dollis Hill]] [[Post Office Research Station]], using algorithms developed by [[W.T. Tutte|Bill Tutte]] and his team of mathematicians.<ref>{{cite web|url=https://uwaterloo.ca/combinatorics-and-optimization/about/professor-william-t-tutte/biography-professor-tutte#bletchley|title=Biography of Professor Tutte - Combinatorics and Optimization|date=13 March 2015|access-date=2017-05-13 |archive-date=2019-08-19 |archive-url=https://web.archive.org/web/20190819115149/https://uwaterloo.ca/combinatorics-and-optimization/about/professor-william-t-tutte/biography-professor-tutte#bletchley|url-status=dead}}</ref> Colossus proved to be efficient and quick against the twelve-rotor Lorenz SZ42 on-line teleprinter cipher machine.

Some influential figures had doubts about his proposed design for the decryption machine, and Flowers  proceeded with the project while partly funding it himself.<ref>{{cite book|last=Boden|first=Margaret Ann|title=Mind as Machine: A History of Cognitive Science|url=https://books.google.com/books?id=yRyETy43AdQC&q=TOMMY+FLOWERS+built+at+his+own+expense+colossus&pg=PA159|publisher=Clarendon Press |location=Oxford|date=2006|page=159|isbn=9780199543168}}</ref><ref>{{cite book |last=Atkinson|first=Paul |date=2010|title=Computer|location=UK|publisher=Reaktion Books|isbn=9781861897374 |url=https://books.google.com/books?id=D5H_OsxEywwC |page=29}}</ref> Like the later [[ENIAC]] of 1946, Colossus did not have a [[stored program]], and was programmed through plugboards and jumper cables. It was faster, more reliable and more capable than the Robinsons, so speeding up the process of finding the Lorenz ''χ'' pin wheel settings. Since Colossus generated the putative keys electronically, it only had to read one tape. It did so with an optical reader which, at 5,000 characters per second, was driven much faster than the Robinsons' and meant that the tape travelled at almost 30 miles per hour (48&nbsp;km/h).<ref>{{Harvnb|Flowers|2006|p=100}}</ref> This, and the clocking of the electronics from the optically read paper tape sprocket holes, completely eliminated the Robinsons' synchronisation problems. Bletchley Park management, which had been sceptical of Flowers's ability to make a workable device, immediately began pressuring him to construct another. After the end of the war, Colossus machines were dismantled on the orders of Winston Churchill,<ref>Verdict of Peace: Britain Between Her Yesterday and the  future, Correlli Barnett, 2002</ref> but GCHQ retained two of them.{{sfn|Copeland|2006|p=173}}