zk-proof-verification

name	zk-proof-verification
description	Help users verify Groth16 zero-knowledge proofs from Circom/snarkjs circuits using Nethereum.ZkProofsVerifier (.NET). Use this skill whenever the user mentions ZK proofs, Groth16, snarkjs, Circom, zero-knowledge verification, BN128 pairing, proof.json, verification_key.json, or public.json in a C#/.NET context.
user-invocable	true

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

Error	Meaning
"Proof is null"	Null proof passed
"Verification key is null"	Null VK passed
"Public inputs array is null"	Null inputs passed
"Verification key IC array is empty"	VK has no IC points
"Expected N public inputs but got M"	IC length doesn't match inputs + 1
"Pairing check failed"	Proof is invalid (tampered or wrong inputs)

Key Types

Type	Purpose
CircomGroth16Adapter	One-liner verification from JSON strings
ZkVerificationResult	Result with IsValid and Error properties

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