Distributed.net is a volunteer 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).

Distributed.net is working on RC5-72 (breaking RC5 with a 72-bit key). The RC5-72 project is on pace to exhaust the keyspace in just under 36 years as of July 2025, although the project will end whenever the required key is found. RC5 has eight unsolved challenges from RSA Security, although in May 2007, RSA Security announced that they would no longer be providing prize money for a correct key to any of their secret key challenges. distributed.net has decided to sponsor the original prize offer for finding the key as a result.

In 2001, distributed.net was estimated to have a throughput of over 30 TFLOPS. , the throughput was estimated to be the same as a Cray XC40, as used in the Lonestar 5 supercomputer, or around 1.25 petaFLOPs.

History

A coordinated effort was started in February 1997 by Earle Ady and Christopher G. Stach II of Hotjobs.com 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.

A new independent effort, named distributed.net, 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.

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".

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".

Client

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

Portions of the source code for the client are publicly available, although users are not permitted to distribute modified versions themselves.

Distributed.net's RC5-72 project is available on the BOINC client through the Moo! Wrapper.

Development of GPU-enabled clients

thumb|350px|Average daily RC5-72 production by platform for 26 May 2024 – 4 January 2025

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 July 2025, GPUs represent almost 89% of all completed work units, and complete more than 95% of all work units each day. For comparison, a 2008-era high-end single CPU working on RC5-72 achieved about 50 million keys/second, representing a very significant advancement for RC5-72. As of July 2025, CUDA clients have completed almost 11% of all work on the RC5-72 project, and perform almost 9% of the work each day. As of January 2025, FireStream clients have completed over 19% of all work on the RC5-72 project.

Timeline of distributed.net projects

{| class="wikitable" style="margin: 1em auto 1em auto"

! Timeline of projects hosted by distributed.net,

|-

|<timeline>

  1. All measures are in pixels

ImageSize = width:800 height:247

PlotArea = left:40 right:0 bottom:20 top:10

AlignBars = justify

DateFormat = mm/dd/yyyy

Period = from:01/01/1997 till:03/18/2026

TimeAxis = orientation:horizontal

ScaleMajor = unit:year increment:1 start:01/01/1997

  1. there is no automatic collision detection,
  2. so shift texts up or down manually to avoid overlap

Define $dy = 25 # shift text to right side of bar

Colors=

id:yellow1 value:rgb(0.867,0.797,0.33)

id:yellow2 value:rgb(0.816,0.714,0.031)

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id:blue1 value:rgb(0.418,0.543,0.950)

id:blue2 value:rgb(0.318,0.484,0.769)

PlotData=

bar:RC5 color:yellow width:25 mark:(line,white) align:center fontsize:S

from:start till:10/19/1997 text:RC5-56 color:yellow1

from:10/29/1997 till:07/14/2002 text:RC5-64 color:yellow2

from:12/03/2002 till:end text:RC5-72 color:yellow3

bar:OGR color:blue1 width:25 mark:(line,white) align:center fontsize:S

from:07/14/2000 till:10/13/2004 text:OGR-24

from:10/26/2008 till:02/24/2009 text:OGR-26

from:02/19/2014 till:11/23/2022 text:OGR-28

bar:&nbsp; color:blue2 width:25 mark:(line,white) align:center fontsize:S

from:08/01/2000 till:10/24/2008 text:OGR-25

from:02/24/2009 till:02/19/2014 text:OGR-27

bar:CSC color:orange width:25 mark:(line,white) align:center fontsize:S

from:11/17/1999 till:01/16/2000 text:CSC

bar:DES color:green width:25 mark:(line,white) align:center fontsize:S

from:01/13/1998 till:02/24/1998 text:DES-II-1

bar:&nbsp;&nbsp;&nbsp; color:yellow1 width:25 mark:(line,white) align:center fontsize:S

from:07/13/1998 till:07/17/1998 text:DES-II-2

bar:&nbsp;&nbsp;&nbsp;&nbsp; color:purple width:25 mark:(line,white) align:center fontsize:S

from:01/18/1999 till:01/19/1999 text:DES-III

</timeline>

|}

; Current

  • RSA Lab's 72-bit RC5 Encryption Challenge started 3 December 2002 — In progress, 15.691% complete as of 18 March 2026 (although RSA Labs has discontinued sponsorship)

; Cryptography

  • 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)
  • 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)
  • 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).
  • RSA Lab's 64-bit RC5 Encryption Challenge — Completed 14 July 2002 (after days and 83% of the key space tested).

; Golomb rulers

  • Optimal Golomb Rulers (OGR-24) — Completed 13 October 2004 (after days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-25) — Completed 24 October 2008 (after days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-26) — Completed 24 February 2009 (after days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-27) — Completed 19 February 2014 (after days, confirmed predicted best ruler)
  • Optimal Golomb Rulers (OGR-28) — Completed 23 November 2022 (after days, confirmed predicted best ruler)

See also

  • RSA Secret-Key Challenge
  • Golomb Ruler
  • DES Challenges
  • Brute force attack
  • Cryptanalysis
  • Key size
  • List of volunteer computing projects
  • Berkeley Open Infrastructure for Network Computing

References

  • Official website