Tandem

Secure Multi-Party Computation (SMPC) is a cryptographic field with the goal of allowing two or more parties to cooperatively compute a result while keeping their inputs private.

Our aim at SINE is to make advanced technology, such as SMPC, available to as many companies as possible. We are especially keen to apply SMPC for the exchange of sustainability data.

Tandem, our SMPC engine, aims at fulfilling our vision by providing an easy to use framework to apply this technology wherever there is a need to share data privately, without a third-party trustee.

Encryptle - Tandem in Action

Tandem is fast enough to be used for practical applications. Check out Encryptle, a Wordle clone that runs entirely over SMPC:

https://encryptle.sine.foundation/

Quick Start

The easiest way to try out Tandem is by using our demo server, either by using our online playground or by connecting to it from your local machine using our command line client:

Online Playground

Go to https://playground.sine.foundation/, where you can execute programs written in Garble. The demo server will use the plaintext metadata that is passed in on the playground as its own "private" input. Of course this defeats the purpose of using Multi-Party Computation, but it is a quick and easy way to try out the engine.

Try the following inputs for the example program provided, which adds two signed 32 bit integers, 3 and 7, and then prints 10i32 as the result:

• Function to Execute: main
• Metadata (Plaintext): 3i32
• Input (Kept Private): 7i32

Command Line Client

You can also connect to the server using the command line client. To do so, install the client binary, create a file containing the garble program and then run the client:

cargo install --features="bin" tandem_http_client
echo "pub fn main(x: u8, y: u8) -> u8 { x + y }" > add.garble.rs
tandem_http_client --function main --input 3u8 --metadata 7u8 add.garble.rs

Overview

This repository consists of four crates:

tandem

This crate includes SINE's Secure Multi-Party Computation engine, Tandem. It is a Rust library, implementing WRK17 as a non-blocking Finite State Machine (FSM).

Please note that, for the time being, Tandem only supports two-party computation.

tandem_garble_interop

The Tandem engine runs Garbled Circuits. As these are cumbersome to write, SINE provides a higher-level programming language: Garble. This crate provides helper functions for translating between the Tandem MPC engine circuit representation and the Garble language circuit representation and types.

tandem_http_client

This crate provides an HTTP client to use the Tandem engine (against a running tandem_http_server server). This crate includes a CLI client, functions targetting WebAssembly and an interactive notebook to test Garble programs during development.

tandem_http_server

This crate provides an HTTP server to use the Tandem engine (with some client). This crate can be used as either a library to construct a server with custom logic or as a binary to run a sample server based on Rocket.

Usage

Basics

Every SMPC session run by the Tandem engine depends on the following data:

1. An MPC program, known to both client and server in plaintext;
2. The name of the function in the MPC program to be executed;
3. The contributor's input, known only to the server (the first argument of the function);
4. The evaluator's input, known only to the client (the second argument of the function).

The Tandem engine runs Garbled Circuits and is agnostic as to what their source is. However, we recommend that all of the above be written in Garble, SINE's programming language, developed specifically for this end. To learn more about Garble and its syntax, take the Language Tour.

In order for the Tandem engine to run, both a server and a client must already be set up and running. Please refer to the documentation on the tandem_http_server and tandem_http_client crates to set them up according to your needs.

Demo

The following is a demonstration of how to run Tandem with a simple function and inputs using the CLI provided by the tandem_http_client crate. Please follow these instructions in order.

1. Starting the Server

Use the commands below to build, install and run the sample server provided by the tandem_http_server crate on localhost:8000:

cargo install --features="bin" tandem_http_server
tandem_http_server

This server acts as a simple 'echo server', which expects the contributor's input to be supplied by the client (as plaintext metadata). While not appropriate in any practical setting, this can be used to test different programs without having to re-deploy servers. This server will accept and execute all MPC programs sent by the client.

To know how to start a server with static configuration, refer to the tandem_http_server documentation.

2. Installing the Client's CLI

On a different terminal tab, use the commands below to install and run the CLI app provided by the tandem_http_client crate:

cargo install --features="bin" tandem_http_client
tandem_http_client <PROGRAM> \
  [OPTIONS] \
  --function <FUNCTION> \
  --input <INPUT> \
  --metadata <METADATA>

The [OPTIONS] include the flag --url, allowing us to set the URL of the HTTP server to use. If none is provided, it defaults to the 'echo server' deployed by SINE: https://echo-server.sine.dev. (Run tandem_http_client --help for more information.)

3. Running the Tandem Engine

We are now ready to gather the four pieces of data needed to run the Tandem engine. Below are the data to be used in this demonstration:

MPC Program

The following Garble program takes two unsigned 8 bit numbers and outputs their sum:

pub fn main(x: u8, y: u8) -> u8 {
    x + y
}

This program is stored in tandem_http_client/tests/.add.garble.rs.

Name of the Function

The function we want to call is main.

Contributor's Input

In this case, the contributor's input will be 110u8 (an unsigned 8-bit integer with a value of 110).

Evaluator's Input

In this case, the evaluator's input will be 57u8 (an unsigned 8-bit integer with a value of 57).

Running Tandem

Use the following command to run the Tandem engine:

tandem_http_client tests/.add.garble.rs \
  --function main \
  --url http://localhost:8000/ \
  --input 110u8 \
  --metadata 57u8

Once Tandem has finished computing, the result will be printed in your terminal:

167u8

(If for some reason this is not what you see, please repeat the steps above and make sure nothing is missing. If that does not work, please reach out.)

Contributions

All contributions and suggestions are welcomed! Please open issues for that effect.