Nethereum.ZkProofsVerifier 7.1.0

Nethereum.ZkProofsVerifier

Native .NET Groth16 proof verification for Circom/snarkjs circuits on the BN128 curve. Verify zero-knowledge proofs entirely in C# without external dependencies on native libraries or JavaScript runtimes.

Overview

Nethereum.ZkProofsVerifier implements the Groth16 zero-knowledge proof verification algorithm using BN128 elliptic curve pairings. It directly consumes the JSON output files produced by snarkjs (proof.json, verification_key.json, public.json), making it straightforward to integrate Circom circuit verification into .NET applications.

Key capabilities:

• One-liner verification via CircomGroth16Adapter.Verify(proofJson, vkJson, publicJson)
• Step-by-step API for parsing and verifying proofs independently
• Tamper detection — modified proofs, inputs, or verification keys are rejected
• EVM-compatible — produces the same results as Solidity Groth16 verifier contracts

Installation

dotnet add package Nethereum.ZkProofsVerifier

Dependencies

• Nethereum.Signer — BN128 curve arithmetic, Fp2/Fp12 extension fields, and optimal Ate pairing

Quick Start

using Nethereum.ZkProofsVerifier.Circom;

// Load snarkjs output files
var proofJson = File.ReadAllText("proof.json");
var vkJson = File.ReadAllText("verification_key.json");
var publicJson = File.ReadAllText("public.json");

// Verify in one line
var result = CircomGroth16Adapter.Verify(proofJson, vkJson, publicJson);

if (result.IsValid)
    Console.WriteLine("Proof verified!");
else
    Console.WriteLine($"Verification failed: {result.Error}");

Usage Examples

Example 1: End-to-End Verification with CircomGroth16Adapter

using Nethereum.ZkProofsVerifier.Circom;

var result = CircomGroth16Adapter.Verify(proofJson, vkJson, publicInputsJson);

if (result.IsValid)
{
    Console.WriteLine("Proof is valid!");
}
else
{
    Console.WriteLine($"Verification failed: {result.Error}");
}

Example 2: Detecting Tampered Proofs

Verification rejects any modification to the proof, inputs, or verification key:

using Nethereum.ZkProofsVerifier.Circom;

// Verify with wrong public inputs
var tamperedPublicJson = "[\"999\"]";
var result = CircomGroth16Adapter.Verify(proofJson, vkJson, tamperedPublicJson);
// result.IsValid == false — inputs don't match what was proven

// Verify with mismatched circuit files
var result2 = CircomGroth16Adapter.Verify(proofJsonA, vkJsonB, publicJsonA);
// result2.IsValid == false — VK doesn't match the proof's circuit

API Reference

CircomGroth16Adapter

The public entry point for verifying snarkjs/Circom proofs. Parses all three JSON files internally and runs the BN128 pairing check.

public static class CircomGroth16Adapter
{
    public static ZkVerificationResult Verify(
        string proofJson,
        string vkJson,
        string publicInputsJson);
}

ZkVerificationResult

Immutable result of a verification attempt.

public class ZkVerificationResult
{
    public bool IsValid { get; }
    public string Error { get; }

    public static ZkVerificationResult Valid();
    public static ZkVerificationResult Invalid(string reason);
}

Verification Algorithm

Internally, the adapter parses the JSON inputs into BN128 curve points and checks the Groth16 pairing equation:

e(-A, B) · e(Alpha, Beta) · e(vkX, Gamma) · e(C, Delta) == 1

Where vkX = IC[0] + sum(IC[i+1] * publicInputs[i]).

All cryptographic types (curve points, field extensions, parsers) are internal implementation details — consumers only interact with CircomGroth16Adapter and ZkVerificationResult.

Supported Formats

Related Packages

• Nethereum.Signer — BN128 curve operations, Fp2/Fp12 extension fields, optimal Ate pairing
• Nethereum.Util — Poseidon hashing (PoseidonHasher with CircomT1/CircomT2/CircomT3 presets) for ZK circuit inputs
• Nethereum.Merkle — Sparse Merkle Binary Tree with PoseidonSmtHasher for ZK-compatible state trees