Cryptology ePrint Archive: Report 2021/375

Round and Communication Balanced Protocols for Oblivious Evaluation of Finite State Machines

Rafael Dowsley and Caleb Horst and Anderson C A Nascimento

Abstract: We propose protocols for obliviously evaluating finite-state machines, i.e., the evaluation is shared between the provider of the finite-state machine and the provider of the input string in such a manner that neither party learns the other's input, and the states being visited are hidden from both. For alphabet size $|\Sigma|$, number of states $|Q|$, and input length $n$, previous solutions have either required a number of rounds linear in $n$ or communication $\Omega(n|\Sigma||Q|\log|Q|)$. Our solutions require 2 rounds with communication $O(n(|\Sigma|+|Q|\log|Q|))$. We present two different solutions to this problem, a two-party one and a setting with an untrusted but non-colluding helper.

Category / Keywords: cryptographic protocols /

Date: received 20 Mar 2021

Contact author: rafael dowsley at monash edu, calebjh at uw edu, andclay at uw edu

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Version: 20210322:193605 (All versions of this report)

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