zero-knowledge-proofs

Zero Knowledge Proofs and how they can be implemented in Quorum

This is a SNARK implementation using libsnark for the following:

ZkPoK{ (R1, R2, R3): Hi = sha256(Ri) and R3 = R1 + R2 }

Read: given H1, H2, H3, prove you know R1, R2, R3 such that R1 is the preimage of H1, R2 is the preimage of H2, R3 is the preimage of H3, and R3 is R1 + R2.

This is an implementation and benchmark of the "Receive" zk-SNARK in the Confidential Transaction scheme from this article: https://media.consensys.net/introduction-to-zksnarks-with-examples-3283b554fc3b.

Code based on https://github.com/ebfull/lightning_circuit.

howto

Required packages

On Ubuntu 16.04 LTS:

  `$ sudo apt-get install build-essential cmake git libgmp3-dev libprocps4-dev python-markdown libboost-all-dev libssl-dev`

On Ubuntu 14.04 LTS:

  `$ sudo apt-get install build-essential cmake git libgmp3-dev libprocps3-dev python-markdown libboost-all-dev libssl-dev`

Installation

./get-libsnark && make

npm install

Running

node index.js startBalance=10000

Follow the prompts.

Generate a key pair
Generate a multi-payment proof (one in and one out)
Verify multi-payment proof
Quit

Generate a new key pair

This creates a new proving key and verification key from the circuit. They are saved to the files:

provingKey
verificationKey

Generate a multi-payment proof

This generates a proof using the proving key as well as the input values:

start balance
incoming payment (currently the user is prompted for 1 incoming payments)
outgoing payment (currently the user is prompted for 1 outgoing payments)
intermediate balance (start balance + incoming payments)
end balance (intermediate balance - outgoing payments)

The proofs are:

start balance + incoming = intermediate balance
end balance + outgoing = intermediate balance

Verify multi-payment proof

Verifies the above proofs

anatomy

src/gadget.hpp exposes the gadget, which is an abstraction of related constraint and witness behavior in a circuit. This gadget uses other gadgets, creates its own constraints, and exposes an interface for building input maps.
src/snark.hpp exposes a loose wrapper around the constraint system and key generation used by test.cpp to construct proofs and verify them as necessary.

License

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Szkered / zero-knowledge-proofs