Efficient Verification of Web-content Searching Through Authenticated Web Crawlers

We consider the problem of verifying the correctness and completeness of the result of a keyword search. We introduce the concept of an authenticated web crawler and present its design and prototype implementation. An authenticated web crawler is a trusted program that computes a specially-crafted signature over the web contents it visits. This signature enables (i) the verification of common Internet queries on web pages, such as conjunctive keyword searches---this guarantees that the output of a conjunctive keyword search is correct and complete; (ii) the verification of the content returned by such Internet queries---this guarantees that web data is authentic and has not been maliciously altered since the computation of the signature by the crawler. In our solution, the search engine returns a cryptographic proof of the query result. Both the proof size and the verification time are proportional only to the sizes of the query description and the query result, but do not depend on the number or sizes of the web pages over which the search is performed. As we experimentally demonstrate, the prototype implementation of our system provides a low communication overhead between the search engine and the user, and fast verification of the returned results by the user.