LangSMC - Language-based Secure Multiparty Computation
Secure multiparty computation (SMC) allows for complex computations over encrypted data. Privacy concerns for cloud applications makes this a highly desired technology and recent performance improvements show that it is practical. To make SMC accessible to non-experts and empower its use in varied applications, many domain-specific compilers are being proposed.
In this work we review the role of these compilers and provide a formal treatment of the core steps that they perform to bridge the abstraction gap between high-level ideal specifications and efficient SMC protocols. Our abstract framework bridges this secure compilation problem across two dimensions:
- Language-based source- to target-level semantic and efficiency gaps
- Cryptographic ideal- to real-world security gaps
We link the former to the setting of certified compilation, paving the way to leverage long-run efforts such as CompCert in future high-assurance SMC compilers. Security is framed in the standard cryptographic sense. This repository reports on the machine-checked formalisation of our results carried out in EasyCrypt, an interactive theorem prover for code-based cryptographic security proofs.
The development is highly modular, and is spread among a considerable number of files. For the sake of illustration in the companion article "A Formal Treatment of the Role of Verified Compilers in Secure Computation", we have produced a simplified, single-file version, that includes all definitions and theorem statements mentioned. Proofs in this file have been replaced to pointers to the corresponding results in the original formalisation. It can be found here.
Repository organisation
We disclose an image of the main EasyCrypt repository under the easycrypt submodule folder.
All EasyCrypt scripts that encompass our formalisation can be found in the proof/src folder.
Building the proof
Requirements
Because the only third-party tool that is used in this project is EasyCrypt, our requirements are essentially the requirements of EasyCrypt. We refer the user to the README file in the EasyCrypt repository - https://www.easycrypt.info/trac/browser/README.md?rev=1.0 - for clear instructions on how to install such dependencies.
Building EasyCrypt
Once all EasyCrypt installation requirements are installed, EasyCrypt can be locally built via
make easycrypt
Verifying the proof
Finally, the formalisation can be verified by typing
make check-proof
which launches an EasyCrypt test script and applies it to all files that comprise the proof.
Proof documentation
A comprehensive description of our EasyCrypt formalisation can be found in http://langsmc.readthedocs.io. However, the documentation can be locally build using the command
make docs-[target]
where target can be either html or latex. This command will
create the appropriate documentation files under the docs/build
folder.