circom-mp-spdz

circom-MP-SPDZ allows parties to perform Multi-Party Computation (MPC) by writing Circom code using the MP-SPDZ framework. Circom code is compiled into an arithmetic circuit and then translated gate by gate to the corresponding MP-SPDZ operators. See the write-up to learn how it works (roughly) and the spec of inputs and outputs: circom-mp-spdz write-up.

NOTE: Now circom-2-arithc also conveniently outputs the Bristol format with corresponding circuit_info (hence the json_arbistol is not necessary anymore).

Supported Circom Type and Op

Type	Op	Supported
Int (sint, cint)	+ Addition	✅
	/ Division	✅
	== Equality	✅
	> Greater Than	✅
	>= Greater Than or Equal	✅
	< Less Than	✅
	<= Less Than or Equal	✅
	* Multiplication	✅
	!= Not Equal	✅
	- Subtraction	✅
	** Exponentiation	✅
	<< Shift Left	✅
	>> Shift Right	✅
	^ Bitwise XOR	❌
	| Bitwise OR	❌
	& Bitwise AND	❌
	% Modulo	❌

NOTE Int can also be used in quantization aware mode, by scaling every input with 2^f and shift left f after every multiplication of two scaled values.

Structure

• circom-2-arithc - we're using commit 800e2d4 not so far from the latest version of circom-2-arithc.
• MP-SPDZ - the custom MP-SPDZ framework to run the MPC protocol. We are using commit 704049e.
• arithc_to_bristol.py - a script to transplie the arithmetic Bristol format to MP-SPDZ .mpc program.
• main.py - the main script to run the circom-mp-spdz. It does the following:
  • Compiles the Circom code to the arithmetic circuit with circom-2-arithc.
  • Generates an MP-SPDZ circuit from the Bristol format circuit with arithc_to_bristol.py.
  • Generates MP-SPDZ input files for each party from the inputs_party_i.json.
  • Performs the computation using MP-SPDZ by running all parties on the local machine.
  • Prints the outputs.
• examples - example circuits to run with circom-mp-spdz.

Installation

Clone the repo

git clone https://github.com/namnc/circom-mp-spdz.git
git clone https://github.com/namnc/circom-2-arithc
git clone https://github.com/mhchia/MP-SPDZ/

Build circom-2-arithc

Go to the circom-2-arithc submodule directory:

cd circom-2-arithc
git checkout 800e2d4

Initialize the .env file:

touch .env
vim .env

and add LOG_LEVEL="DEBUG"

Build the compiler:

cargo build --release

Build MP-SPDZ

You may need to install some dependencies, see: MP-SPDZ.

Go to the MP-SPDZ submodule directory:

cd ../MP-SPDZ
git checkout 704049e

Build the MPC VM for semi protocol

make -j8 semi-party.x
# Make sure `semi-party.x` exists
ls semi-party.x

How to run

We have two examples available

• ops_tests - a benchmark of supported ops for sint
• naive_search - a benchmark of naive search

In both examples, we assume there are only 2 parties. You will find the following files in each example directory:

• circuit.circom - the circom code representing the circuit to be computed by all parties
• mpc_settings.json - the settings file defining for each party:
  • the party's name in string format
  • which input signals they should provide
  • which output signals they can learn the value of
• inputs_party_0.json - the input file for party 0. It must contain all the inputs for party 0
• inputs_party_1.json - the input file for party 1. It must contain all the inputs for party 1

See the section Input files in the write-up for more details.

You can run these examples by following the instructions in the root directory.

# Go back to the root directory of circom-mp-spdz
cd ..
python main.py {circuit_name}

• {circuit_name} is the name of the circuit you want to run. Can either be ops_tests or naive_search.
• Intermediate files will be stored in the outputs/{circuit_name} directory. NOTE: we also output circuit.mpc which you can use to run with the original MP-SPDZ.
• Outputs are directly printed to the console.

Example ops_tests

python main.py ops_tests

You can see the the intermediate files in the outputs/ops_tests directory. And you should see the following outputs in the console:

...
========= Computation has finished =========


Outputs: {...}

Example naive_search

python main.py naive_search

You can see the the intermediate files in the outputs/naive_search directory. And you should see the following outputs in the console:

...
========= Computation has finished =========


Outputs: {...}

Moving Forward

The circuit.mpc program in the respective output folder can be used with MP-SPDZ in an appropriate deployment settings.