Abstract. Performance of secure computation is still often an obstacle to its practical adaption. There are different protocols for secure computation that compete for the best performance. In this paper we propose automatic protocol selection which selects a protocol for each operation resulting in a mix with the best performance so far. Based on an elaborate performance model, we propose an optimization algorithm and an efficient heuristic for this selection problem. We show that our mixed protocols achieve the best performance on a set of use cases. Furthermore, our results underpin that the selection problem is so complicated and large in size, that a programmer is unlikely to manually make the optimal selection. Our proposed algorithms nevertheless can be integrated into a compiler in order to yield the best (or near-optimal) performance.

Abstract-Secure Computation (SC) enables secure distributed computation of arbitrary functions of private inputs. It has many useful applications, e.g. benchmarking or auctions. Several general protocols for SC have been proposed and recently been implemented in a number of compilers and frameworks. These compilers or frameworks implement one general SC protocol and then require the programmer to implement the function he wants the protocol to compute.Performance remains a challenge for this approach and it has been realized early on that special protocols for important problems can deliver superior performance.In this paper we propose a new intermediate language (L1) for optimizing SC compilers which enables efficient implementation of special protocols potentially mixing several general SC protocols.We show by three case studies -one for computation of the median, one for weighted average, one for division -that special protocols and mixed-protocol implementations in our language L1 can lead to superior performance. Moreover, we show that only a combined view on algorithm and cryptographic protocol can discover SCs with best run-time performance.

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Many advancements in the area of Secure Multi-Party Computation (SMC) protocols use improvements in communication complexity as a justification. We conducted an experimental study of a specific protocol for a real-world sized problem under realistic conditions and it suggests that the practical performance of the protocol is almost independent of the network performance. We argue that our result can be generalized to a whole class of SMC protocols.

Recent databases are implemented as in-memory columnstores. Adjustable encryption offers a solution to encrypted database processing in the cloud.We show that the two technologies play well together by providing an analysis and prototype results that demonstrate the impact of mechanisms at the database side (dictionaries and their compression) and cryptographic mechanisms at the adjustable encryption side (order-preserving, homomorphic, deterministic and probabilistic encryption).