Zk Proof Verification

ZK Proof Verification — Nethereum.ZkProofsVerifier

When to Use This

Use this skill when a user wants to:

• Verify a Groth16 zero-knowledge proof in .NET
• Consume snarkjs/Circom output (proof.json, verification_key.json, public.json)
• Check if a ZK proof is valid before submitting a transaction
• Cross-validate native .NET verification against a Solidity Groth16 verifier
• Detect tampered proofs, inputs, or verification keys

Required Packages

dotnet add package Nethereum.ZkProofsVerifier

Core Concept

Groth16 is the most widely used ZK proof system in Ethereum. Nethereum.ZkProofsVerifier verifies proofs natively in .NET by checking a BN128 elliptic curve pairing equation. It directly consumes the three JSON files that snarkjs produces after proving a Circom circuit.

The recommended entry point is CircomGroth16Adapter.Verify() — a single static method that parses all three JSON files and returns a result. This hides all cryptographic internals (curve points, field extensions, BouncyCastle types) behind a clean API.

One-Liner Verification (Recommended)

using Nethereum.ZkProofsVerifier.Circom;

var proofJson = File.ReadAllText("proof.json");
var vkJson = File.ReadAllText("verification_key.json");
var publicJson = File.ReadAllText("public.json");

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

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

Tamper Detection

Verification rejects any modification to proof, inputs, or VK:

// Wrong public inputs — verification fails
var tamperedPublicJson = "[\"999\"]";
var result = CircomGroth16Adapter.Verify(proofJson, vkJson, tamperedPublicJson);
// result.IsValid == false

Error Messages

Key Types

All parsing and cryptographic types (curve points, field extensions, verifier internals) are internal — consumers only interact with CircomGroth16Adapter and ZkVerificationResult.

Supported Formats

Only snarkjs JSON output is supported:

• proof.json — G1/G2 curve points (pi_a, pi_b, pi_c)
• verification_key.json — trusted setup output (vk_alpha_1, vk_beta_2, vk_gamma_2, vk_delta_2, IC)
• public.json — decimal string array of public circuit inputs

For full documentation, see: https://docs.nethereum.com/docs/consensus-and-cryptography/guide-zk-proof-verification