Round and Communication Balanced Protocols for Oblivious Evaluation of Finite State Machines
This work addresses secure computation challenges in cryptography, offering efficient protocols for privacy-preserving finite-state machine evaluation, though it is incremental in optimizing round and communication complexity.
The paper tackles the problem of obliviously evaluating finite-state machines with privacy for both the machine and input providers, achieving a protocol with only 2 rounds and communication complexity of O(n(|Σ|+|Q|log|Q|)), improving upon previous linear round or higher communication costs.
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 $|Σ|$, number of states $|Q|$, and input length $n$, previous solutions have either required a number of rounds linear in $n$ or communication $Ω(n|Σ||Q|\log|Q|)$. Our solutions require 2 rounds with communication $O(n(|Σ|+|Q|\log|Q|))$. We present two different solutions to this problem, a two-party one and a setting with an untrusted but non-colluding helper.