This patent purports to cover the rather obvious idea of "using substantially unique identifiers to identify data items, whereby identical data items have the same identifiers":
http://www.patentstorm.us/patents/5978791.html It was filed in October 1997, and is owned by Altnet, who are currently using it to sue Streamcast (creators of Morpheus), and, if they prevail or of Streamcast caves, could conceivably attack other P2P networks, including Freenet: http://arstechnica.com/news.ars/post/20060815-7508.html Now it is hard to believe that prior art wouldn't exist for such an obvious idea, claim one is a text book definition of a hash function which have been around for decades, claim 2 would seem to describe a hashtable, also a notion with clear prior art going back decades, claim 5 seems to describe the operation of a cache, and so on. But then the claims discuss using this technique to retrieve things over a network. Now, one might argue that simply applying a common computer science technique to a distributed situation is not novel (I don't believe you can get a valid patent simply by combining two other things you didn't invent), but it would be really useful to find some robust examples of requesting files by their hashes over a network that pre-date October 1997. I have heard that the Xanadu project may have something in 1990, but haven't got any specific references. Is anyone aware of anything concrete? Ian.
