EIPs/EIPS/eip-1923.md

---
eip: 1923
title: zk-SNARK Verifier Registry Standard
author: Michael Connor <michael.connor@uk.ey.com>, Chaitanya Konda <chaitanya.konda@uk.ey.com>, Duncan Westland <duncan.westland@uk.ey.com>
discussions-to: https://github.com/ethereum/EIPs/issues/1923
type: Standards Track
category: ERC
status: Draft
created: 2018-12-22
requires: 165, 196, 197
---

## Simple Summary


A standard interface for a "Verifier Registry"'" contract, through which all zk-SNARK verification activity can be registered.

## Abstract
The following standard allows for the implementation of a standard contract API for the registration of zk-SNARKs ("Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge"), also known as "proofs", "arguments", or "commitments".

TODO: Which functionality is exposed in this standard interface?

## Motivation
zk-SNARKs are a promising area of interest for the Ethereum community. Key applications of zk-SNARKs include:
- Private transactions
- Private computations
- Ethereum scaling through proofs of 'bundled' transactions

A standard interface for registering all zk-SNARKs will allow applications to more easily implement private transactions, private contracts, and scaling solutions; and to extract and interpret the limited information which gets emitted during zk-SNARK verifications.

:warning: TODO: Explain the motivation for standardizing a registry, other than simply standardizing the verifier interactions.

⚠️ TODO: Explain the benefits to and perspective of a consumer of information. I.e. the thing that interfaces with the standard verifier registry.

## Specification
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.


```solidity
pragma solidity ^0.5.6;

/// @title EIP-XXXX zk-SNARK Verifier Registry Standard
/// @dev See https://github.com/EYBlockchain/zksnark-verifier-standard
///  Note: the ERC-165 identifier for this interface is 0xXXXXXXXXX.
/// ⚠️ TODO: Set the interface identifier
interface EIP-XXXX /* is ERC165 */ {

  event NewProofSubmitted(bytes32 indexed _proofId, uint256[] _proof, uint64[] _inputs);

  event NewVkRegistered(bytes32 indexed _vkId);

  event NewVerifierContractRegistered(address indexed _contractAddress);

  event NewAttestation(bytes32 indexed _proofId, address indexed _verifier, bool indexed _result);


  function getVk(bytes32 _vkId) external returns (uint256[] memory);

  function registerVerifierContract(address _verifierContract) external returns (bool);

  function registerVk(uint256[] calldata _vk, address[] calldata _verifierContracts) external returns (bytes32);

  function submitProof(uint256[] calldata _proof, uint64[] calldata _inputs, bytes32 _vkId) external returns (bytes32);

  function submitProof(uint256[] calldata _proof, uint64[] calldata _inputs, bytes32 _vkId, address _verifierContract) external returns (bytes32);

  function submitProofAndVerify(uint256[] calldata _proof, uint64[] calldata _inputs, bytes32 _vkId, address _verifierContract) external returns (bytes32);

  function attestProof(bytes32 _proofId, bytes32 _vkId, bool _result) external;

  function attestProofs(bytes32[] calldata _proofIds, bytes32[] calldata _vkIds, bool[] calldata _results) external;

  function challengeAttestation(bytes32 _proofId, uint256[] calldata _proof, uint64[] calldata  _inputs, address _verifierContract) external;

  function createNewVkId(uint256[] calldata _vk) external pure returns (bytes32);

  function createNewProofId(uint256[] calldata _proof, uint64[] calldata _inputs) external pure returns (bytes32);

}
```
### Interface
``` solidity
interface ERC165 {
    /// @notice Query if a contract implements an interface
    /// @param interfaceID The interface identifier, as specified in ERC-165
    /// @dev Interface identification is specified in ERC-165. This function
    ///  uses less than 30,000 gas.
    /// @return `true` if the contract implements `interfaceID` and
    ///  `interfaceID` is not 0xffffffff, `false` otherwise
    function supportsInterface(bytes4 interfaceID) external view returns (bool);
}
```

## Rationale

⚠️ TODO: Add Rationale section.

### Backwards Compatibility

⚠️ TODO: Add Backwards Compatibility section.

### Test Cases

Truffle tests of example implementations are included in this Repo.

⚠️ TODO: Reference specific test cases because there are many currently in the repository.


## Implementations
Detailed example implementations and Truffle tests of these example implementations are included in this Repo.

⚠️ TODO: Update referenced verifier registry implementations so that they are ready-to-deploy or reference deployed versions of those implementations. At current, the referenced code specifically states "DO NOT USE THIS IN PRODUCTION".

⚠️ TODO: Provide reference to an implementation which interrogates a standard verifier registry contract that implements this standard.


## References

⚠️ TODO: Update references and confirm that each reference is cited (parenthetical documentation not necessary) in the text.

**Standards**

1. ERC-20 Token Standard. ./eip-20.md

1. ERC-165 Standard Interface Detection. ./eip-165.md
2. ERC-173 Contract Ownership Standard (DRAFT). ./eip-173.md
3. ERC-196 Precompiled contracts for addition and scalar multiplication on the elliptic curve alt_bn128. ./eip-196.md
4. ERC-197 Precompiled contracts for optimal ate pairing check on the elliptic curve alt_bn128. ./eip-197.md
5. Ethereum Name Service (ENS). https://ens.domains
6. RFC 2119 Key words for use in RFCs to Indicate Requirement Levels. https://www.ietf.org/rfc/rfc2119.txt

##### Educational material:  zk-SNARKs

1. Zcash. What are zk-SNARKs? https://z.cash/technology/zksnarks.html
2. Vitalik Buterin. zk-SNARKs: Under the Hood. https://medium.com/@VitalikButerin/zk-snarks-under-the-hood-b33151a013f6
3. Christian Reitweissner. zk-SNARKs in a Nutshell. https://blog.ethereum.org/2016/12/05/zksnarks-in-a-nutshell/
4. Ben-Sasson, Chiesa, Tromer, et. al. Succinct Non-Interactive Zero Knowledge for a von Neumann Architecture. https://eprint.iacr.org/2013/879.pdf

##### Notable applications of zk-SNARKs

1. EY. Implementation of a business agreement through Token Commitment transactions on the Ethereum mainnet. https://github.com/EYBlockchain/ZKPChallenge
2. Zcash. https://z.cash
3. Zcash. How Transactions Between Shielded Addresses Work. https://blog.z.cash/zcash-private-transactions/

##### Notable projects relating to zk-SNARKs

1. libsnark: A C++ Library for zk-SNARKs ("project README)". https://github.com/scipr-lab/libsnark
2. ZoKrates: Scalable Privacy-Preserving Off-Chain Computations. https://www.ise.tu-berlin.de/fileadmin/fg308/publications/2018/2018_eberhardt_ZoKrates.pdf
3. ZoKrates Project Repository. https://github.com/JacobEberhardt/ZoKrates
4. Joseph Stockermans. zkSNARKs: Driver's Ed. https://github.com/jstoxrocky/zksnarks_example
5. Christian Reitweissner - snarktest.solidity. https://gist.github.com/chriseth/f9be9d9391efc5beb9704255a8e2989d

##### Notable 'alternatives' to zk-SNARKs - areas of ongoing zero-knowledge proof research

1. Vitalik Buterin. STARKs. https://vitalik.ca/general/2017/11/09/starks_part_1.html
2. Bu ̈nz, Bootle, Boneh, et. al. Bulletproofs. https://eprint.iacr.org/2017/1066.pdf
3. Range Proofs. https://www.cosic.esat.kuleuven.be/ecrypt/provpriv2012/abstracts/canard.pdf
4. Apple. Secure Enclaves. https://developer.apple.com/documentation/security/certificate_key_and_trust_services/keys/storing_keys_in_the_secure_enclave
5. Intel Software Guard Extensions. https://software.intel.com/en-us/sgx


## Copyright

Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).