Massachusetts Institute of Technology
Existing crypto-based Private Information Retrieval (PIR) schemes are either limited in the set of queries they can per-form, or have prohibitively large performance overheads in making query comparisons. On the other hand, most previous tamper-resistant hardware schemes can support more general queries and have lower performance overheads, but need to trust that the query program will not leak information about the user query. The authors introduce stream-ascend in this paper, a processor that executes complex stream queries securely even if the query matching program is not trusted and would leak the query when executed on conventional secure processors. Stream-Ascend is based on Ascend, a recently-proposed tamper-resistant processor for untrusted programs.