ZK Architecture

ZK Proof Architecture

SIP uses Noir as the primary ZK circuit language for zero-knowledge proofs.

Overview

SIP requires ZK proofs for three core operations:

Funding Proof - Prove sufficient funds without revealing balance
Validity Proof - Prove intent authorization without revealing sender
Fulfillment Proof - Prove correct execution without revealing path

Framework Selection

Decision: Noir

Noir provides the best balance of:

Developer experience (Rust-like syntax)
Backend flexibility (UltraPlonk, Groth16, Halo2)
Universal setup (no per-circuit trusted setup)
Rich standard library

Evaluation Matrix

Criteria	Circom	Noir	Halo2
Security	9/10	7/10	7/10
DX	5/10	9/10	4/10
Performance	9/10	7/10	8/10
Trust Assumptions	5/10	8/10	10/10
Weighted Score	7.05	7.75	6.55

Circuit Specifications

Funding Proof

Proves user has sufficient balance without revealing actual amount.

fn funding_proof(
    // Public inputs
    commitment_hash: pub Field,
    minimum_amount: pub u64,

    // Private inputs
    actual_balance: u64,
    blinding_factor: Field,
) {
    // Prove balance is sufficient
    assert(actual_balance >= minimum_amount);

    // Prove commitment is correctly formed
    let computed = pedersen_commit(
        actual_balance as Field,
        blinding_factor
    );
    assert(commitment_hash(computed) == commitment_hash);
}

Validity Proof

Proves intent is authorized without revealing sender.

fn validity_proof(
    // Public inputs
    intent_hash: pub Field,
    sender_commitment: pub Field,

    // Private inputs
    sender_address: Field,
    signature: [u8; 64],
    blinding: Field,
) {
    // Verify signature
    let is_valid = ecdsa_verify(
        sender_address,
        intent_hash,
        signature
    );
    assert(is_valid);

    // Verify sender commitment
    let address_hash = poseidon::hash_1([sender_address]);
    let computed = pedersen_commit(address_hash, blinding);
    assert(commitment_hash(computed) == sender_commitment);
}

Fulfillment Proof

Proves solver correctly executed the swap.

fn fulfillment_proof(
    // Public inputs
    intent_id: pub Field,
    output_commitment: pub Field,
    min_output: pub u64,
    recipient_stealth: pub Field,

    // Private inputs
    output_amount: u64,
    output_blinding: Field,
    tx_hash: Field,
) {
    // Prove output meets minimum
    assert(output_amount >= min_output);

    // Prove commitment correctness
    let computed = pedersen_commit(
        output_amount as Field,
        output_blinding
    );
    assert(commitment_hash(computed) == output_commitment);

    // Prove delivery to stealth address
    // (binding to tx_hash proves execution)
}

Standard Library

Noir provides built-in support for:

Primitive	Usage
Pedersen hash	Commitment scheme
SHA256	Compatibility
Poseidon	Field-efficient hashing
ECDSA	Wallet signatures
EdDSA	Alternative signatures
Schnorr	Stealth derivation

Architecture

flowchart TB
    subgraph SDK["SDK (TypeScript)"]
        subgraph PP["ProofProvider Interface"]
            Mock["MockProvider"]
            Noir["NoirProvider"]
        end
    end

    SDK --> TestPath
    SDK --> ProdPath

    subgraph TestPath["Testing Path"]
        MockProofs["Mock Proofs<br/>(Testing)"]
    end

    subgraph ProdPath["Production Path"]
        NoirJS["Noir / NoirJS<br/>(Production)"]
    end

    NoirJS --> UP["UltraPlonk Backend"]
    NoirJS --> G16["Groth16 Backend"]

    style SDK fill:#312e81,stroke:#8b5cf6,stroke-width:2px
    style PP fill:#4c1d95,stroke:#a78bfa
    style TestPath fill:#1e1b4b,stroke:#8b5cf6
    style ProdPath fill:#4c1d95,stroke:#a78bfa,stroke-width:2px
    style UP fill:#22c55e,stroke:#86efac
    style G16 fill:#22c55e,stroke:#86efac

SDK Integration

ProofProvider Interface

interface ProofProvider {
  generateFundingProof(params: FundingProofParams): Promise<ProofResult>
  generateValidityProof(params: ValidityProofParams): Promise<ProofResult>
  generateFulfillmentProof(params: FulfillmentProofParams): Promise<ProofResult>
  verifyProof(proof: ZKProof, publicInputs: Field[]): Promise<boolean>
}

MockProofProvider

For testing and development:

const sip = new SIP({
  network: 'testnet',
  proofProvider: new MockProofProvider()
})

NoirProofProvider (Planned)

For production:

const sip = new SIP({
  network: 'mainnet',
  proofProvider: new NoirProofProvider({
    wasmPath: '/circuits/funding.wasm',
    circuitPath: '/circuits/'
  })
})

Performance

Operation	Mock	Noir (estimated)
Funding proof gen	<1ms	2-5s
Validity proof gen	<1ms	2-5s
Fulfillment proof gen	<1ms	2-5s
Verification	<1ms	~10ms

Browser Support

NoirJS enables client-side proof generation:

import { compile, createProver } from '@noir-lang/noir_js'

// Load circuit
const circuit = await compile('/circuits/funding.nr')
const prover = await createProver(circuit)

// Generate proof in browser
const proof = await prover.prove({
  actual_balance: 1000n,
  blinding_factor: randomField(),
  commitment_hash: commitmentHash,
  minimum_amount: 500n
})

Risk Mitigation

Risk	Mitigation
Less battle-tested	Simple circuits, formal verification
Performance gaps	Start with UltraPlonk, can switch
Smaller ecosystem	Core primitives well-supported