The authors propose that this is possible by caching lots of copies at many sites on the Internet, never removing articles from these caches, comparing the copies at different sites to detect and repair damage, and making it hard to find all of the copies. In the authors' proposal, there are a large number of archives keeping copies of various journal articles. When a new issue of a journal comes out, each library's archive site retrieves the new material from the publisher's web site and stores it in the archive. At random intervals, an archive may conduct a poll of other sites, in order to verify the integrity of its collection. Archives which receive this invitation must decide whether to participate.
Participation requires the computation of a hash of the contents, and is therefore expensive.
Consequently, an archive will decline to participate in some polls and participate in others. If the archive chooses to participate, it will, at some point before the duration is up, choose a random verifier, and prepend the verifier and the challenge to the collection and compute a hash. It multicasts the challenge, verifier, remaining duration, and the hash to all other parties. The challenge and the verifier prevent replays, forcing the hash to be recomputed if the archive chooses to participate. Each participant tallies the votes by recomputing the hash using the verifier of the received votes.