Hash and sign with a ZK proof. Assuming public signing key.
Implemented for arbitrary JSON.
The interface is ugly. Also intends user to copy from console logs. The point is to implement an end-to-end working hash and sign zk proof for integration into other projects.
To install the necessary packages etc, run yarn install.
The circuit-specific files are provided to the react frontend through express.
To run the example, start the express server in file-server and the react application:
# Run fileserver:
cd src/file-server
node index.js
# Start react
yarn start
The circuit and related files are located in the folder src/zkproof.
To fix ssl issue:
export NODE_OPTIONS=--openssl-legacy-provider
yarn start
Instructions to compile a circuit are here: https://github.com/iden3/snarkjs#10-compile-the-circuit
We use groth16
The circuit is compiled for 2 versions
- small input:
max_json_size=25; good for tests- compiled with pot14 p-tau's
- larger input:
max_json_size=1400- compiled with pot19 p-tau's
The large one is heavy, takes longer to prove/verify, requires larger files, and more powers of tau.
To generate powers of tau for pot19, I ran a ceremony. But these files are too big to commit to github.
Can generate pot19 files using instructions here: https://github.com/iden3/snarkjs#1-start-a-new-powers-of-tau-ceremony
circuit_1400.zkey is also too large.
Can generate this file again by using pot19 files and steps below (from the snarkjs documentation).
Our curcuit has many more constaints than examples or intended use cases due to our desire to send the json string as we do.
Larger JSON --> More constraints --> Requires more powers of tau.
Must have total constraints < 2**p-taus
More constraints requires more powers of tau.
circom circuit_1400.circom --r1cs --wasm --sym
node circuit_1400_js/generate_witness.js circuit_1400_js/circuit_1400.wasm ./input_1400.json ./witness_1400.wtns
# check witness
snarkjs wtns check circuit_1400.r1cs witness_1400.wtns
snarkjs groth16 setup circuit_1400.r1cs pot19_final.ptau circuit_1400.zkey
# Then I skip some production specific steps for phase 2 contirbutions
# step 21. verify the zkey
snarkjs zkey verify circuit_1400.r1cs pot19_final.ptau circuit_1400.zkey
# 22. export the zkey
snarkjs zkey export verificationkey circuit_1400.zkey verification_key_1400.json
# 23. proof
snarkjs groth16 prove circuit_1400.zkey witness_1400.wtns proof_1400.json public_1400.json
# 24. verify the proof
snarkjs groth16 verify verification_key_1400.json public_1400.json proof_1400.json