Cryptology ePrint Archive: Report 2018/404

Enforcing ideal-world leakage bounds in real-world secret sharing MPC frameworks

Josť Bacelar Almeida and Manuel Barbosa and Gilles Barthe and Hugo Pacheco and Vitor Pereira and Bernardo Portela

Abstract: We give a language-based security treatment of domain-specific languages and compilers for secure multi-party computation, a cryptographic paradigm that enables collaborative computation over encrypted data. Computations are specified in a core imperative language, as if they were intended to be executed by a trusted-third party, and formally verified against an information-flow policy modelling (an upper bound to) their leakage. This allows non-experts to assess the impact of performance-driven authorized disclosure of intermediate values.

Specifications are then compiled into multi-party protocols. We formalize protocol security using (distributed) probabilistic information-flow and prove that compilation is security-preserving: protocols do not leak more than allowed by the source policy. The proof exploits a natural but previously missing correspondence between simulation-based cryptographic proofs and (composable) probabilistic non-interference.

Finally, we extend our framework to justify leakage cancelling, a domain-specific optimization that allows to, first, write an efficiently computable specification that fails to meet the allowed leakage upper-bound, and then apply a probabilistic pre-processing that brings the overall leakage to within the acceptable range.

Category / Keywords: Domain-specific languages, Privacy, Security, Semantics, Type systems, Verification, Multi-party computation, Secure compilation

Original Publication (with major differences): 31st IEEE Computer Security Foundations Symposium

Date: received 30 Apr 2018, last revised 1 May 2018

Contact author: vitor m pereira at inesctec pt

Available format(s): PDF | BibTeX Citation

Version: 20180510:201327 (All versions of this report)

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