Taming the round efficiency of cryptographic protocols for private web search schemes

Private web search (PWS) schemes allow users to find information on the internet while preserving their privacy. Among them, cryptographic PWS schemes guarantee strong privacy at the cost of performance. Their design principle is that each user takes a list of ciphertexts as inputs from its predecessor and forwards a shuffled list of the input to its successor. This idea is quite reasonable but requires O(n) round complexity with respect to the number of users n. Because these cryptographic PWS schemes are interaction-intensive, this long delay causes network latency and dictates the local computational cost. This linear round complexity is the main obstacle for deploying these schemes in real-world applications.