staff blogs

distributed.net staff keep (relatively) up-to-date logs of their activities in .plan files. These were traditionally available via finger, but we've put them on the web for easier consumption.

2010/12/28

A near-miss (or perhaps a near-hit?)

Filed under: project status @ 21:00 UTC

Dear friends,

We recently received the first true “false positive” work unit of the RC5-72 project. These are a rare find.

In the interests of client speed, only the first “block” of the encrypted text is decrypted and evaluated for a solution. This means that it’s possible for a key which isn’t the correct key to report as a false positive because although it doesn’t decrypt the text, it does yield a plaintext which matches “The unkn” for the first eight bytes.

The decrypt of the packet was “The unkn…O.k.V>..3W.R..lW.]*e.sc.:-…..u…..cN.&.0.N.” The lucky participant is known as 門村 (“Gate Village”) and will be receiving a T-shirt from us soon. He is a researcher in Japan running dnetc on a Windows system with a Stream client.

As some participants may recall, we also identified a similar ‘false positive’ during the previous RC5-64 project. Finding these are exciting because they help to validate that the project is working properly and is still on track to find the real solution.

It also represents an interesting datapoint regarding the RC5 algorithm. There’s been much speculation and napkin scribbling on just how frequently such false positives might present themselves. The general consensus seemed to be that such an occurrence is extremely improbable. A brute-force search is really the only way to conclusively determine the likelihood of such false positives.

Keep on crunching! ]:8)