erikp0 / ppac

A privacy-preserving access control system using secret-sharing and zkSnarks

About

This is a prototype implementation of a distributed key-management system with privacy-preserving access control.

Key management is distributed among policy enforcement (PEP) nodes that use secret-sharing and various threshold cryptography protocols to generate, manage and re-encrypt key material.

Access policies to keys are encoded as zero-knowledge proof statements in the ZoKrates format. A requester then creates a zk-snark proof over the given statement and uses this proof as authorization. The proof is checked in a smart contract in a (private) Ethereum blockchain.

In short:

• Keys are secret-shared and thus partial compromise of PEP nodes is tolerated
• A requester uses a privacy-preserving authorization with minimal release of information

The implementation consists of three parts

• The PEP node implementation secret-store
• The client implementation client
• The smart contract in contracts

Building

Make sure that the submodule is pulled: git submodule update --init.

Prerequisites:

• Rust installation supporting Rust 2018 with stable and nightly toolchains available to Cargo

All build commands and steps are abbreviated via make

Type make to see list of all targets,

client             Builds the client
client-test        Runs client tests
secretstore        Builds secretstore server
secretstore-test   Runs secretstore server tests

The binaries for make client and make secretstore can be found in target/client and target/secretstore respectively.

secretstore-test is fast to build and run while client-test will take a while to compile at the first run as a full secretstore instance will be built to run tests against.

Docker

There are docker images for the client and secretstore server available.

They can be build manually via docker build -f [client|secretstore].Dockerfile ..

Pre-built images are available from the GitHub package repository:

docker pull docker.pkg.github.com/erikp0/ppac/secretstore:latest

and

docker pull docker.pkg.github.com/erikp0/ppac/client:latest

Demo

See demo directory.

License

Parts of this work use code from Parity's secret-store implementation licensed under GPL3.