Open main menu is a distributed computing effort that is attempting to solve large scale problems using otherwise idle CPU or GPU time. It is governed by Distributed Computing Technologies, Incorporated (DCTI), a non-profit organization under U.S. tax code 501(c)(3).
The logo
Type of site
Volunteer computing
OwnerDistributed Computing Technologies, Inc.
LaunchedFebruary 1997
Current statusActive is working on RC5-72 (breaking RC5 with a 72-bit key),[1] and OGR-28 (searching for the optimal 28-mark Golomb ruler).[2] The RC5-72 project is on pace to exhaust the keyspace in just under 150 years, although the project will end whenever the required key is found. Both problems are part of a series: OGR is part of an infinite series; RC5 has eight unsolved challenges from RSA Security, although in May 2007, RSA Security announced[3] that they would no longer be providing prize money for a correct key to any of their secret key challenges. has decided to sponsor the original prize offer for finding the key as a result.[4]

In 2001, was estimated to have a throughput of over 30 TFLOPS.[5] By 2009, throughput was estimated to be much higher.[6] As of August 2019, the throughput was estimated to be the same as the Lonestar 5 supercomputer,[7] or around 1.25 petaFLOPs.[8]


A coordinated effort was started in February 1997 by Earle Ady and Christopher G. Stach II of and New Media Labs, as an effort to break the RC5-56 portion of the RSA Secret-Key Challenge, a 56-bit encryption algorithm that had a $10,000 USD prize available to anyone who could find the key. Unfortunately, this initial effort had to be suspended as the result of SYN flood attacks by participants upon the server.[9]

A new independent effort, named, was coordinated by Jeffrey A. Lawson, Adam L. Beberg, and David C. McNett along with several others who would serve on the board and operate infrastructure. By late March 1997 new proxies were released to resume RC5-56 and work began on enhanced clients. A cow head was selected as the icon of the application and the project's mascot.[10]

The RC5-56 challenge was solved on October 19, 1997 after 250 days. The correct key was "0x532B744CC20999" and the plaintext message read "The unknown message is: It's time to move to a longer key length".[11]

The RC5-64 challenge was solved on July 14, 2002 after 1,757 days. The correct key was "0x63DE7DC154F4D039" and the plaintext message read "The unknown message is: Some things are better left unread".[12]

The search for OGRs of order 24, 25, 26, and 27 were completed by on 13 October 2004, 25 October 2008, 24 February 2009, and 19 February 2014 respectively.[13][14][15][16]


"DNETC" is the file name of the software application which users run to participate in any active project. It is a command line program with an interface to configure it, available for a wide variety of platforms.[17] refers to the software application simply as the "client". As of April 2019, volunteers running 32-bit Windows with ATI/AMD Stream enabled GPUs have contributed the most processing power to the RC5-72 project[18] and volunteers running 64-bit GNU/Linux have contributed the most processing power to the OGR-28 project.[19]

Portions of the source code for the client are publicly available, although users are not permitted to distribute modified versions themselves.[20]'s RC5-72 and OGR-28 projects are available on the BOINC client through the Moo! Wrapper and yoyo@home projects respectively.[21][22]

Development of GPU-enabled clientsEdit

Average daily RC5-72 production by platform for 21 January 2017 – 5 January 2018[23]

In recent years, most of the work on the RC5-72 project has been submitted by clients that run on the GPU of modern graphics cards. Although the project had already been underway for almost 6 years when the first GPUs began submitting results, as of March 2018, GPUs represent 78% of all completed work units,[24] and complete nearly 93% of all work units each day.[23]

In late 2007, work began on the implementation of new RC5-72 cores designed to run on NVIDIA CUDA-enabled hardware, with the first completed work units reported in November 2008. On high-end NVIDIA video cards, upwards of 600 million keys/second has been reported.[25] Considering a very high end single CPU working on RC5-72 may achieve 50 million keys/second, the CUDA advancement represents a performance increase of roughly 1000%. As of March 2018, CUDA clients have completed more than 8% of all work on the RC5-72 project,[24] and currently complete almost 29% of all work units each day.[23]
  • ATI
Similarly, near the end of 2008, work began on the implementation of new RC5-72 cores designed to run on ATI Stream-enabled hardware. Some of the products in the Radeon HD 5000 and 6000 series provide key rates in excess of 1.8 billion keys/second.[26] As of March 2018, Stream clients have completed more than 52% of all work on the RC5-72 project,[24] and currently complete more than 10% of all work units each day.[23]
  • OpenCL
An OpenCL client entered beta testing in late 2012 and was released in 2013. As of March 2018, OpenCL clients have completed 17% of all work on the RC5-72 project, and currently complete 53% of all work units each day.[23] No breakdown of OpenCL production by GPU manufacturer exists (AMD, Nvidia, and Intel GPUs support OpenCL).

Timeline of projectsEdit

Timeline of projects hosted by, as of March 2018
  • RSA Lab's 72-bit RC5 Encryption Challenge — In progress, 5.710% complete as of 22 April 2019[27] (although RSA Labs has discontinued sponsorship)
  • Optimal Golomb Rulers (OGR-28) — In progress, ~61.92% complete as of 22 April 2019[2]
  • RSA Lab's 56-bit RC5 Encryption Challenge — Completed 19 October 1997 (after 250 days and 47% of the key space tested).
  • RSA Lab's 56-bit DES-II-1 Encryption Challenge — Completed 23 February 1998 (after 39 days)[28]
  • RSA Lab's 56-bit DES-II-2 Encryption Challenge — Ended 15 July 1998 (found independently by the EFF DES cracker after 2.5 days)[29]
  • RSA Lab's 56-bit DES-III Encryption Challenge — Completed 19 January 1999 (after 22.5 hours with the help of the EFF DES cracker)
  • CS-Cipher Challenge — Completed 16 January 2000 (after 60 days and 98% of the key space tested).[30]
  • RSA Lab's 64-bit RC5 Encryption Challenge — Completed 14 July 2002 (after 1726 days and 83% of the key space tested).[31]
Golomb rulers
  • Optimal Golomb Rulers (OGR-24) — Completed 13 October 2004[32] (after 1552 days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-25) — Completed 24 October 2008[33] (after 3006 days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-26) — Completed 24 February 2009[34] (after 121 days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-27) — Completed 19 February 2014[35] (after 1822 days, confirmed predicted best ruler)

See alsoEdit


  1. ^ "RC5-72 project page".
  2. ^ a b "OGR-28 Overall Project Stats". Retrieved 22 January 2017.
  3. ^ "RSA Laboratories Secret-Key Challenge". Archived from the original on 2007-07-06.
  4. ^ "RC5-72 Continuation Announcement".
  5. ^ " mailing list archive".
  6. ^ " 2009: 76.1 Billion passwords per second".
  7. ^
  8. ^
  9. ^ Glave, James (1997-03-03). "Macho Computing at Root of RSA Contest Flap". Wired.
  10. ^ "What's with all the cows?".
  11. ^ " Project RC5". Retrieved 2019-04-23.
  12. ^ " Project RC5". Retrieved 2019-04-23.
  13. ^ " staff blogs – 2004 – November – 01". Retrieved 2019-04-23.
  14. ^ " staff blogs – 2008 – October – 25". Retrieved 2019-04-23.
  15. ^ " staff blogs – 2009 – February – 24". Retrieved 2019-04-23.
  16. ^ " staff blogs – 2014 – February – 25". Retrieved 2019-04-23.
  17. ^ " Client Downloads". Retrieved 2019-04-22.
  18. ^ " - RC5-72 CPU Participation". Retrieved 2019-04-23.
  19. ^ " - OGR-28 CPU Participation". Retrieved 2019-04-23.
  20. ^ "Public source code".
  21. ^ "Moo! Wrapper". Moo! Wrapper. Retrieved 2019-03-08.
  22. ^ "yoyo@home". Retrieved 2019-04-22.
  23. ^ a b c d e Calculated by subtracting the completed work units as of 21 January 2017 from the totals on 5 January 2018, creating a 348-day average.
  24. ^ a b c "RC5-72 / CPU Participation". Retrieved 22 January 2017.
  25. ^ "Client Speeds Database (GPU RC5-72 search)". Retrieved 27 February 2014.
  26. ^ "Benchmark results for Radeon HD 5870". MrJackson2000. April 1, 2010.
  27. ^ "RC5-72 Overall Project Stats". Retrieved 7 January 2017.
  28. ^ David C. McNett (24 February 1998). "The secret message is..." Retrieved 27 February 2014.
  29. ^ "The Electronic Frontier Foundation DES Cracker FAQ". EFF. 16 July 1998. Archived from the original on 7 May 2017. Retrieved 27 February 2014.
  30. ^ "CSC project page". 16 January 2000. Retrieved 25 February 2016.
  31. ^ "History & Timeline".
  32. ^ " is proud to announce the completion of OGR-24!". 2004-11-01.
  33. ^ " is proud to announce the completion of OGR-25!". 2008-10-25.
  34. ^ "Howdy all,". 2009-02-24.
  35. ^ "OGR-27 Completion Announcement". 2014-02-25.

External linksEdit