SAN FRANCISCO, July 31 - Briefly buoyed by their Supreme Court victory on file sharing, Hollywood and the recording industry are on the verge of confronting more technically sophisticated opponents.

At a computer security conference in Las Vegas on Thursday, an Irish software designer described a new version of a peer-to-peer file-sharing system that he says will make it easier to share digital information anonymously and make detection by corporations and governments far more difficult.

Others have described similar efforts to build a so-called darknet that aims to shield the identities of those sharing information. The issue is complicated by the fact that the small group of technologists designing the new systems say their goal is to create tools to circumvent censorship and political repression -- not to abet copyright violation.

Such a stand is certain to test the impact of the Supreme Court ruling in June against Grokster and StreamCast Networks, publishers of peer-to-peer file-sharing software, a number of legal specialists and industry executives said. The court ruled unanimously that the publishers could be held liable for the copyright infringement that their software enabled in the sharing of pirated movies and music.