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« Efficient and Secure Multiparty Computation from Fixed-Key Block Ciphers

Efficient and Secure Multiparty Computation from Fixed-Key Block Ciphers

March 15, 2019, 11:45 AM - 12:15 PM


Barrister's Hall - first floor

Boston University Law School

765 Commonwealth Avenue

Boston, MA 02215

Xiao Wang, MIT and Boston University

Many implementations of secure computation use fixed-key AES; this results in substantial performance benefits due to hardware support for AES and the ability to avoid recomputing the AES key schedule. Surveying these implementations, however, we find that most utilize AES in a heuristic fashion; in the best case this leaves a gap in the security proof, but in many cases we show it allows for explicit attacks.

Motivated by this unsatisfactory state of affairs, we initiate a comprehensive study of how to use fixed-key block ciphers for secure computation — in particular for OT extension and circuit garbling — efficiently and securely. Our results provide end-to-end security proofs for implementations of secure-computation protocols based on fixed-key block ciphers (modeled as random permutations). Perhaps surprisingly, at the same time our work also results in noticeable performance improvements over the state-of-the-art.

Work by Chun Guo, Jonathan Katz, Xiao Wang, and Yu Yu.