Editing Colossus computer (section)

==Reconstruction==
[[File:ColossusRebuild 11.jpg|right|thumb|upright=1.35|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.]]
A team led by Tony Sale built a fully functional reconstruction<ref>{{cite web|url=http://www.codesandciphers.org.uk/lorenz/rebuild.htm|title=Colossus Rebuild - Tony Sale|website=Codesandciphers.org.uk|access-date=26 October 2017}}</ref><ref>* {{cite web |last= Sale |first= Tony |author-link= Tony Sale |title= Video of Tony Sale talking about rebuilt Colossus 2008-6-19 |year= 2008 |url= https://www.codesandciphers.org.uk/lorenz/pods/coltalk_2.html | access-date= 13 May 2017}}</ref> of a Colossus Mark 2 between 1993 and 2008.<ref name="The Colossus Computer"/><ref name="auto"/> In spite of the blueprints and hardware being destroyed, a surprising amount of material had survived, mainly in engineers' notebooks, but a considerable amount of it in the U.S. The optical tape reader might have posed the biggest problem, but [[Arnold Lynch|Dr. Arnold Lynch]], its original designer was able to redesign it to his own original specification. The reconstruction is on display, in the historically correct place for Colossus No. 9, at [[The National Museum of Computing]], in H Block [[Bletchley Park]] in [[Milton Keynes]], Buckinghamshire.

In November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for The National Museum of Computing, a Cipher Challenge<ref>{{cite web |title=Cipher Challenge |url=http://www.tnmoc.org/cipher1.htm |access-date=1 February 2012 |archive-url= https://web.archive.org/web/20080801175842/http://www.tnmoc.org/cipher1.htm |archive-date=1 August 2008}}</ref> pitted the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode three messages enciphered using the [[Lorenz SZ42]] and transmitted from radio station DL0HNF in the ''Heinz Nixdorf MuseumsForum'' computer museum. The challenge was easily won by [[radio amateur]] Joachim Schüth, who had carefully prepared<ref>{{cite web |url=http://www.schlaupelz.de/SZ42/SZ42_software.html |title=SZ42 codebreaking software |website=Schlaupelz.de |access-date=26 October 2017}}</ref> for the event and developed his own signal processing and code-breaking code using [[Ada (programming language)|Ada]].<ref>{{cite web |url=http://www.adacore.com/home/ada_answers/lorenz-code/ |title=Cracking the Lorenz Code |website=Ada Answers |publisher=AdaCore |access-date=26 October 2017 |archive-url=https://web.archive.org/web/20120208010213/http://www.adacore.com/home/ada_answers/lorenz-code/|archive-date=8 February 2012 |url-status=dead}}</ref> The Colossus team were hampered by their wish to use World War II radio equipment,<ref>{{cite news |title=Colossus loses code-cracking race |url=http://news.bbc.co.uk/1/hi/technology/7098005.stm |date=16 November 2007 |work=BBC News |access-date=2 January 2010 |first=Mark |last=Ward}}</ref> delaying them by a day because of poor reception conditions. Nevertheless, the victor's 1.4&nbsp;GHz laptop, running his own code, took less than a minute to find the settings for all 12 wheels. The German codebreaker said: "My laptop digested ciphertext at a speed of 1.2&nbsp;million characters per second—240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8&nbsp;MHz for Colossus. That is a remarkable speed for a computer built in 1944."<ref>{{cite web |title=German Codebreaker receives Bletchley Park Honours |date=27 Jan 2008 |publisher=Bletchley Park National Codes Centre |url=http://www.bletchleypark.org.uk/news/docview.rhtm/487682 |access-date=2012-04-07 |archive-url= https://web.archive.org/web/20130102214431/http://www.bletchleypark.org.uk/news/docview.rhtm/487682 |archive-date=2 January 2013 |url-status=dead}}</ref>

The Cipher Challenge verified the successful completion of the rebuilding project. "On the strength of today's performance Colossus is as good as it was six decades ago", commented Tony Sale. "We are delighted to have produced a fitting tribute to the people who worked at Bletchley Park and whose brainpower devised these fantastic machines which broke these ciphers and shortened the war by many months."<ref>{{cite web |title=Latest Cipher Challenge News 16.11.2007 |website=TNMoC - Cipher Challenge! |url=http://www.tnmoc.org/cipher7.htm |archive-url= https://web.archive.org/web/20080418084956/http://www.tnmoc.org/cipher7.htm |archive-date=2008-04-18}}</ref>

[[File:Frontal view of the reconstructed Colossus at The National Museum of Computing, Bletchley Park.jpg|center|thumbnail|upright=3.35|Front view of the Colossus reconstruction showing, from right to left: (1) The "bedstead" containing the message tape in its continuous loop and with a second one loaded. (2) The J-rack containing the Selection Panel and Plug Panel. (3) The K-rack with the large "Q" switch panel and sloping patch panel. (4) The double S-rack containing the control panel and, above the image of a postage stamp, five two-line counter displays. (5) The electric typewriter in front of the five sets of four "set total" decade switches in the C-rack.<ref>{{cite web |last=Sale |first=Tony |author-link=Anthony Sale |title=The Colossus its purpose and operation |website=Codesandciphers.org.uk |url=http://www.codesandciphers.org.uk/virtualbp/fish/colossus.htm |access-date=26 October 2017}}</ref>]]