Paper 2016/546

An Unconditionally Hiding Auditing Procedure for Multi-Party Computations

Lucas Schabhüser, Denise Demirel, and Johannes Buchmann

Abstract

In this work an unconditionally hiding auditing procedure for computations on documents stored in distributed fashion is introduced. There is only one multi-party computation (MPC) scheme providing auditability which computationally protects the inputs of the computations. Building on this, we propose a computationally hiding solution that uses bilinear maps and therefore produces no additional overhead in the online phase. In addition, we introduce a second variation that is the first auditable MPC scheme providing unconditional (or information-theoretic) hidingness. We achieve this by combining bilinear maps with unconditionally hiding commitments leading to only a small overhead in the online phase. We prove our solutions secure and give arguments for practicability and efficiency. The auditing procedures presented here are an important contribution since distributed storage solutions, e.g. cloud of clouds, allow for information-theoretic confidentiality. Using our technique, they can be extended to perform auditable computations on the data stored.