MPC Millionaires

Alice, Bob and Charlie are all millionaires.

They would like to know their total wealth and how they compare to each other over 3 years, without disclosing their actual wealth to each other.

This is a somewhat more elaborated version of the famous Yao's Millionaires' problem which demonstrates the ability of CipherCompute EAP to perform confidential computations mixing arithmetic and non-linear operations.

Hack it !

The code is heavily documented and under MIT license as it is meant to be hacked for your purpose.

It is actually very easy to generalize this code to most confidential Key Performance Indicators comparisons across entities with minor modifications.

Do not hesitate to open issues and PRs to improve the quality of this code and its documentation.

Editing and testing

Once you have cloned this repository locally, edit the code; we recommend that you use the free VSCode and rust-analyzer extension.

To check the validity of your code, simply run cargo build. The build process outputs WASM which is what is actually fed as an intermediate representation to the CipherCompute engine.

To facilitate testing without having to run CipherCompute EAP, 2 facilities are provided via 2 scripts:

• emulate.sh will pick up the input data in the data/inputs directory and output its results in the data/outputs directory. These directories contain one file per player. This scripts perform the same emulation as that provided on the CipherCompute UI.

• test.sh will run the unit tests of the main.rs file. For a test written

  #[test]
   fn test_example() {
       // An example of a successful test
       // which input and expected output data are located
       // in the `fixtures/success_test` folder
       cosmian_std::test!("success_test");
       // If you change any data in the input or output files,
       // the test will fail
   }

  The input data will be picked up from the fixtures/success_test/inputs directory and the outputs will be compared to those of the fixtures/success_test/outputs directory.

Testing inside the CipherCompute MPC engine

1. Make a change and test it using ./simulate.sh

2. commit the change to the local git and note the git commit

3. Then use the git-daemon.sh script to launch a git daemon which exposes this project at git://localhost:9418/mpc_millionaires

From the UI on the CipherCompute EAP version

4. Create/update a computation using the git URL above and the git commit you want to test
5. Run the computation from the UI

See the CipherCompute EAP Quick Start Guide on how to use its UI to configure a computation.