Project RC5

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Project RC5


The "Bovine" RC5 effort was formed to take the responsibilities of coordinating and maintaining the RC5 servers that are needed to distribute key blocks to work on to all of the participating client programs. We depend heavily (entirely) on the participation of people like yourself, as we intend to solve this project via the use of brute force, trying every possible key there is.

We know this method works! On 19 October 1997 at 1325 UTC, we found the correct solution for the RSA Labs 56-bit secret-key challenge (RC5-32/12/7). The key was 0x532B744CC20999, and it took us 250 days to locate.

Then, on 14 July 2002 at 0150 UTC we found the winning key for the RSA Labs 64-bit secret-key challenge (RC5-32/12/8). That key was 0x63DE7DC154F4D039 and took us 1,757 days to locate. As of 03 December 2002, we're now working on the 72-bit RSA Labs secret-key challenge (RC5-32/12/9). In summary:

  • RC5-56: 'The unknown message is: It's time to move to a longer key length'
  • RC5-64: 'The unknown message is: Some things are better left unread'
  • RC5-72: ??? (in progress; you can help!)

In May 2007, RSA Labs announced that Secret Key Challenge would be discontinued. Fortunately, due to the continued interest in our RC5-72 project we have decided to privately sponsor the prize and operate the RC5-72 project as before. You can read about this in bovine's 2008-Sep-08 plan and in bovine's 2007-May-21 plan.

Current speeds and statistics for individual participants or teams are available at our dedicated stats server. You can find out our current overall speed for the entire network at our network status page.

If you have any technical support questions regarding the operations of your client, then please send mail to or email submission form. Be sure to also check out the FAQ-o-Matic to see if your question has already been answered.

The Prize

RSA Labs was offering a US$10,000 prize to the group that wins this contest. The distribution of the cash was to be as follows:

  • $1000 to the winner
  • $1000 to the winner's team (or to the winner if not on a team)
  • $6000 to a non-profit organization chosen by all participants
  • $2000 to for building the network and supplying the code

The recipient non-profit is chosen by means of a meritocratic vote through an extension of the stats database. We will distribute the RC5-72 prize money based on your votes, with one vote per work unit per person. You can also see how we've distributed the prize money on previous RC5 projects: RC5-56 and RC5-64.

General Links Pertaining to RC5

Recommended Links

Visit our Press Room for more information and to read the announcements.