tommenstein is correct in that encryption does not help people who are sharing data. the riaa could do a search and download stuff from you, get your ip, sue you etc. I know, me and some guys got a letter from the RIAA when we were in school

encryption (via public key for each client) helps riaa from seeing who _else_ is downloading material, but they could still set up a 'sting' server that has songs and try to bait you that way. but thats what you get on a public network, too bad.