It has taken 331,252 volunteers four years to solve the RC5-64 Secret-Key challenge organised by RSA Laboratories.

Established in 1997, RSA Laboratories' Secret-Key Challenge was staged to quantify the strength of symmetric encryption algorithms such as DES and the RC5 algorithm with various key sizes.

By sponsoring an actual contest, RSA Laboratories helps the industry confirm theoretical estimates, and through this constant evaluation, vendors are motivated to continue to improve their security solutions.

The winner, the distributed.net consortium, utilised the idle time of computers throughout the world to search through the list of all possible 64-bit keys for RSA Security's RC5 algorithm to find the one secret key selected at random by RSA Laboratories that decrypts a given message correctly.

RSA Laboratories sponsors a series of cryptographic challenges that allow individuals or groups to attempt to solve various encryption "puzzles" for cash prizes. The RC5-64 Challenge is one of a series of contests held to determine the difficulty of finding a symmetric encryption key using an exhaustive "brute forcing" search (trial-and-error). Previous contests include the DES Challenge, the RC5-40 Challenge and the RC5-56 Challenge.

Distributed.net cofounder and president David McNett said the contest shows how collective computing power can be applied to security technology with ordinary PCs.

Chief scientist at RSA Laboratories Burt Kaliski said those involved in the challenge were certainly persistent.

"Their work helps the industry confirm how much work is involved to search exhaustively for a key and how a huge volume of computing time can be harnessed," he said.

"The various challenges we sponsor are very useful for tracking the state of cryptographic achievements and helping ensure that organisations are maintaining the highest levels of security to protect their most critical data assets."