The Data Encryption Standard Challenge was launched in 1997 by RSA Laboratories (part of RAS Security Company) and was the first of 3 DES challenges.
The contest was meant to demonstrate to the US government that 56-bit DES is an ineffective form of encryption for international use, and only stronger forms will ensure security. The goal of the challenge was to decrypt secret messages which had been encrypted with DES.
DES Challenge I was solved on 17.June 1997 after a period of 140 days by DESCHALL, a group led by Rocke Verser, Matt Curtin, and Justin Dolske. They officially cracked DES for the first time using a distributed computing project on the Internet. A 'brute force attack' was carried out, which means that they were simply testing one possible key after another, knowing that the total number of key was 2^56 (over 72 quadrillion).
The architecture of the distributed system focused on a single 'key-server' which acted as the brain of the whole system. Each Client had to contact the server via the internet to request work and report the results. According to the DESCHALL project, more than 78.000 unique IP addresses were recorded by the key-server as having participated to some extent.
In July, then a new record was established, when the Electronic Frontier Foundation (EFF) won DES Challenge II-2 cracking a message in just 56 hours using the first unclassified hardware for cracking DES messages, called 'Deep Crack'.
With the end of DES Challenge III it was proven that it was now feasible to break DES encrypted messages in less than 24 hours, which could also be understood as an immediate call for action, knowing that DES was still in use for numerous purposes in public live relying on previous statement by the US-Government, that the DES was secure. From that day on there was no need for additional DES Challenges, but the RSA Labs are still active today and are awarding prizes for solving various security related problems.
Electronic Frontier Foundation (DES Cracker)
RSA Labs (actual cryptographic challenges)