RC5-64

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RC5-64 is one of the largest-running distributed computing projects, second only to SETI@home. Distributed.net does hold the record for longest-running project, though: RC5-64 has been running for over 1,000 days — almost 3 years. It is taking quite awhile to solve this encryption problem because, chances are, every data block needs to be processed until the key is found; there is no way of knowing what block it is in so all blocks must be tested. This is known as the "brute force" solution method. The odds of when the key could be found are virtually unknown; it could be found in the next hour or next year. However, Distributed.net does have the time it will take to find the key if the key is in the last block processed. Since it's taken 1,000 days to get through 30% of the keyspace, it may take another 3,000 days to find the key.

Unlike SETI@home and a few other distributed computing projects, RC5-64 is partially open source. This has led to some problems, as people can use the parts of the code that are given and try to make their computer appear to be processing more blocks, or even make their computer appear that it is processing data blocks when it's really not. The latter would be especially detrimental to the project. The key is hidden in just one block. If that block was returned as negative when it really did have the key, the project would have to completely start over. Something similar could happen unintentionally if someone's computer crashed while it was processing a block. That block then may be "lost," and wouldn't be redistributed for at least 90 days. However, there are options on the software that allows the user to have the computer save the block every so often, so the liklihood of this happening is very slim.

RC5-64 is a finite project, as it will end once the correct key is found. It is likely, though, that RSA will issue another encryption challenge, perhaps featuring a 72-bit code, and yet again try to convince the US Government that standards should be raised to 128-bit encryption. All that is certain is that Distributed.net will be involved in many more challenges and projects to come, as the organization wants to increase distributed computing usage and augment idle computer power and CPU cycles for something useful.

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