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ZoKrates pyCrypto

This repository contains accompanying crypto application code for the zkSNARKs toolbox ZoKrates.

This is a proof-of-concept implementation. It has not been tested for production.

Install

Make sure you are running a python 3 runtime.

git clone https://github.com/Zokrates/pycrypto.git
pip install -r requirements.txt

Example

Compute SNARK-friendly Pedersen hash

Let's create a simple demo, called demo.py:

from zokrates_pycrypto.gadgets.pedersenHasher import PedersenHasher

preimage = bytes.fromhex("1616")
# create an instance with personalisation string
hasher = PedersenHasher(b"test")
# hash payload
digest = hasher.hash_bytes(preimage)
print(digest)
# x:2685288813799964008676827085163841323150845457335242286797566359029072666741,
# y:3621301112689898657718575625160907319236763714743560759856749092648347440543

# write ZoKrates DSL code to disk
path = "pedersen.code"
hasher.write_dsl_code(path)

# write witness arguments to disk
path = "pedersen_witness.txt"
witness = hasher.gen_dsl_witness_bytes(preimage)
with open(path, "w+") as f:
    f.write(" ".join(witness))

We can now can run this python script via:

python demo.py

which should create the ZoKrates DSL code file pedersen.code, as well as a file which contains the witness pedersen_witness.txt.

Make sure you have the zokrates executable in the same folder. Then run the following command to compile the SNARK-circuit:

./zokrates compile -i pedersen.code

We can now conpute the witness:

`cat zokrates_witness.txt | ./zokrates compute-witness`

Witness:

~out_1 3621301112689898657718575625160907319236763714743560759856749092648347440543
~out_0 2685288813799964008676827085163841323150845457335242286797566359029072666741

As you can easily verify we get the same pedersen hash point for the Python and ZoKrates implementation.

Create and verify Eddsa signature

Let's create a simple demo, called demo.py:

import hashlib

from zokrates_pycrypto.eddsa import PrivateKey, PublicKey
from zokrates_pycrypto.field import FQ
from zokrates_pycrypto.utils import write_signature_for_zokrates_cli

if __name__ == "__main__":

    raw_msg = "This is my secret message"
    msg = hashlib.sha512(raw_msg.encode("utf-8")).digest()

    # sk = PrivateKey.from_rand()
    # Seeded for debug purpose
    key = FQ(1997011358982923168928344992199991480689546837621580239342656433234255379025)
    sk = PrivateKey(key)
    sig = sk.sign(msg)

    pk = PublicKey.from_private(sk)
    is_verified = pk.verify(sig, msg)
    print(is_verified)

    path = 'zokrates_inputs.txt'
    write_signature_for_zokrates_cli(pk, sig, msg, path)

We can now can run this python script via:

python demo.py

which should create a file called zokrates_inputs.txt.

We can now create a small ZoKrates DSL file which wraps the existing verifyEddsa function in the standard library.

from "ecc/babyjubjubParams" import BabyJubJubParams
import "signatures/verifyEddsa.code" as verifyEddsa
import "ecc/babyjubjubParams.code" as context

def main(private field[2] R, private field S, field[2] A, u32[8] M0, u32[8] M1) -> (bool):

	BabyJubJubParams context = context()
	
    bool isVerified = verifyEddsa(R, S, A, M0, M1, context)

	return isVerified

After compiling this file we can now pass our input arguments into witness generation:

cat zokrates_inputs.txt | ./zokrates compute-witness

CLI Usage

pycrypto also provides a simple command-line interface to make it easy to integrate the used crypto primitives into your existing application code.

Some examples:

Compute SNARK-friendly Pedersen hash

python cli.py hash 3755668da8deabd8cafbe1c26cda5a837ed5f832665c5ef94725f6884054d9083755668da8deabd8cafbe1c26cda5a837ed5f832665c5ef94725f6884054d908

where the first argument denotes the preimage as a hexstring.

Create and verify an EdDSA signature

python cli.py keygen
# => 37e334c51386a5c92152f592ef264b82ad52cf2bbfb6cee1c363e67be97732a ab466cd8924518f07172c0f8c695c60f77c11357b461d787ef31864a163f3995
# Private and public key

python cli.py sig-gen 37e334c51386a5c92152f592ef264b82ad52cf2bbfb6cee1c363e67be97732a 11dd22
# => 172a1794976d7d0272148c4be3b7ad74fd3a82376cd5995fc4d274e3593c0e6c 24e96be628208a9800336d23bd31318d8a9b95bc9bd8f6f01cae207c05062523
# R and S element of EdDSA signature

python cli.py sig-verify ab466cd8924518f07172c0f8c695c60f77c11357b461d787ef31864a163f3995 11dd22 172a1794976d7d0272148c4be3b7ad74fd3a82376cd5995fc4d274e3593c0e6c 24e96be628208a9800336d23bd31318d8a9b95bc9bd8f6f01cae207c05062523
# => True

Contributing

We happily welcome contributions. You can either pick an existing issue, or reach out on Gitter.

Unless you explicitly state otherwise, any contribution you intentionally submit for inclusion in the work shall be licensed as above, without any additional terms or conditions.

Setup

First install the development packages via pip install -r requirements-dev.txt.

In addition this repo uses the python package pre-commit to make sure the correct formatting (black & flake) is applied and all tests pass. You can install it via pip install pre-commit.

Then you just need to call pre-commit install.

License

This repo is released under the GNU Lesser General Public License v3.