Identity-based （ID-based） ring signature has drawn great concerns in recent years and many ID-based ring signature schemes have been proposed until now. Unfortunately, all of these ID-based ring signatures are constructed from bilinear pairings, a powerful but computationally expensive primitive. Hence, ID-based ring signature without pairing is of great interest in the field of cryptography. In this paper, the authors firstly propose an ID-based ring signature scheme based on quadratic residues. The proposed scheme is proved to be existentially unforgeable against adaptive chosen message-and-identity attack under the random oracle model, assuming the hardness of factoring. The proposed scheme is more efficient than those which are constructed from bilinear pairings.
The paper proposes a novel hardware-based private information retrieval （HWPIR） protocol. By partially reshuffling previously accessed items in each round, instead of frequently reshuffling the whole database, the scheme makes better use of shuffled data copies and achieves the computation overhead at O（/N/K）,where N and k are the sizes of the database and secure storage respectively. For securestorage with moderate size, e.g. k = O（/N）, the overhead is 0（4/N）. The result is much better than the state-of-art schemes （as compared to e.g. O（log2N））. Without increasing response time and communication cost, the proposed protocol is truly practicable regardless of the database size. The security and preformance of the protocol is formally analyzed.
