Japanese page is here .
Cracking Challenge is a cryptographic contest of RC5-64 bit posted by RSA Data Security, Ltd. . Even though currently 128 is available for RC5, the U.S. government offers users including Windows NT other than North America and Canada less secure 40-bit encryption keys only. Because a 64-bit encryption key creates enormous 18,440 million billion combinations, so to recruit spare cycles on many machines across the Internet is a very effective way. This simple but reliable way works and has decrypted 1,620 million billion out of about 18,000 million billion keys with the speed of 71.4 billion per second. Distribute.net has the feature that ranking is listed by each team and each participant.