is a world-wide distributed computing effort that is attempting to solve large scale problems using idle CPU time. It started out as an effort to break RC5-56, a 56-bit encryption algorithm
that had a $10,000 USD
prize available to anyone who could find the key. That challenge was solved on October 19 1997
after 250 days. The next project was the RC5-64 challenge which took nearly five years to complete before the correct key was found on July 14 2002
Currently distributed.net is working on RC5-72 (a higher key length version of the original challenge) and the OGR-25 project, which is searching for 25 point Optimal Golomb Rulers.