# Zero-Knowledge Agents (ZKA)

> Privacy-preserving protocols for autonomous AI agent interactions. Noir circuits verified on Aztec L2 and any EVM chain.

ZKA defines the privacy layer using Noir zero-knowledge circuits compiled via ACIR. Primary deployment on Aztec L2 with auto-generated Solidity verifiers for any EVM chain.

## Core Principle

Agents can prove claims without revealing underlying data. Payments happen without exposing amounts or parties. Reputation accrues without leaking transaction history.

## Implementation Stack

| Layer | Technology |
|-------|-----------|
| Circuit Language | Noir v1.0 |
| Proving Backend | Barretenberg (UltraHonk) |
| Curve | BN254 / Grumpkin |
| Hash Function | Poseidon2 |
| Arithmetization | PLONKish |
| Recursion | Goblin Plonk |
| Primary Deployment | Aztec L2 |
| EVM Verification | Auto-generated Solidity verifier |

## Protocol Family

| Protocol | Purpose | Status |
|----------|---------|--------|
| ZKA/Pay | Privacy-preserving agent payments | Implemented (Noir) |
| ZKA/Coord | Recursive coordination proofs | Implemented (Noir) |
| ZKA/Compute | Verifiable private computation | Future |
| ZKA/Attest | ZKC credential binding to notes | Specified (§5) |
| ZKA/Reputation | Privacy-preserving reputation | Future |

## ZKA/Pay: Private Transfers

Noir transfer circuit with hidden amounts and parties:
- Public inputs: nullifier, output_commitment, merkle_root, context, asset_commitment
- Private inputs: note fields, spending key, Merkle path
- Constraints: Merkle membership, nullifier correctness, ownership, value conservation, asset conservation
- Verification: <300k gas on any EVM chain; native on Aztec

## ZKA/Coord: Recursive Proofs

Multi-agent workflow verification via recursive Noir proofs:
- Each agent produces proof embedding verification of upstream inputs
- Recursive composition via Goblin Plonk (Aztec) or manual verification (standalone)
- Final proof attests entire DAG executed correctly
- Verification: <500k gas regardless of recursion depth

## Multi-Chain Verification

Noir → ACIR → Multiple backends:
- Barretenberg (UltraHonk): Aztec + EVM (production)
- Halo 2 (IPA): Setup-free chains (in development)
- Groth16: Via ACIR→R1CS compilation
- Verification on: Aztec, any EVM chain, Starknet, zkVerify, Cosmos, Solana

## Architecture

```
Noir Circuits (ACIR)
    │
    ├── Barretenberg (UltraHonk) → Aztec L2 (native privacy) + EVM (Solidity verifier)
    ├── Halo 2 (future) → Setup-free chains
    └── Groth16 (future) → Cosmos, other targets
```

## Circuit Library

```
noir/
├── zka_lib/              # Shared primitives (Poseidon2, keys, Merkle)
├── zka_transfer/         # Transfer circuit (ZKA/Pay)
├── zka_withdrawal/       # Withdrawal circuit
├── zka_balance/          # Balance proof circuit
├── zka_coordination/     # Coordination circuit (ZKA/Coord)
├── zka_credential/       # ZKC credential binding
└── zka_bridge_*/         # Namada/Penumbra bridge circuits
```

## Specification

- [Full Specification](/spec/)
- [Extended Documentation](/llms-full.txt)

## Version

ZKA Specification Version: 0.6.1