Final Report Summary - PPP (Protecting and Preserving Human Knowledge for Posterity) The amount and variety of content being published online is growing at anexplosive rate. Online publishing enables content to reach a much largeraudience than paper publishing but offers no guarantee of long-term accessto the content. The PPP Project investigates techniques for building alarge, reliable peer-to-peer system for the preservation of onlinepublished material. The system consists of a large number of low-cost,persistent web caches (peers) that cooperate to detect and repair damageby voting in "opinion polls" on the content of their cached documents.The peers are autonomous and mutually suspicious. Project activitiesinclude 1) investigating defenses against adversaries whose goal is toattack the preservation process; 2) performing a foundational study of theinterconnections between identity, trust, and reputation models inpeer-to-peer systems; 3) investigating the use of estimates of peerdiversity to increase the fault and attack tolerance of peer-to-peersystems; and 4) developing, analyzing, implementing, and testing newprotocols that address a large spectrum of data preservation challengesincluding: the high frequency of updates of online government documents,the large volumes of scientific data, and the privacy concerns of sensitiveuser data.This work is being evaluated using a real testbed of over 200 librariesaround the world with the support of publishers representing thousands oftitles. The broader impact of the work is that all electronic materialpreserved through the system including academic journals, governmentdocuments and web articles, and scientific data will remainaccessible to generations of citizens for both research and educationpurposes.
