LP-0033Finalquantumq-chainpost-quantumdilithiumkyber

LP-033: Quantum VM

Abstract

The Quantum VM runs the Q-chain, a dedicated chain for post-quantum cryptographic operations. All transactions on the Q-chain use ML-DSA (FIPS 204, formerly CRYSTALS-Dilithium) signatures and ML-KEM (FIPS 203, formerly CRYSTALS-Kyber) key encapsulation. The Q-chain serves as the PQ key registry for the entire Lux network, allowing any chain to verify PQ signatures by referencing Q-chain state via Warp messages (LP-021).

Specification

Account Model

Q-chain accounts use Dilithium-3 public keys (1952 bytes) instead of ECDSA:


Account {
    pubkey      [1952]byte  // Dilithium-3 public key
    nonce       uint64
    balance     uint256
    codeHash    [32]byte    // for PQ smart contracts
    storageRoot [32]byte
}

Account addresses are derived as keccak256(dilithiumPubkey)[12:] (20 bytes, compatible with EVM tooling).

Transaction Format


QTx {
    nonce       uint64
    to          [20]byte
    value       uint256
    data        []byte
    gasLimit    uint64
    gasPrice    uint256
    signature   [3293]byte  // Dilithium-3 signature
}

Signature verification uses the NTT-accelerated ML-DSA verifier (LP-029).

PQ Key Registry

The Q-chain maintains a registry mapping addresses (on any Lux chain) to their PQ public keys:


Registry {
    mapping(address => DilithiumPubkey) public pqKeys;
    mapping(address => KyberPubkey)     public encryptionKeys;
}

Any user can register their PQ keys on the Q-chain. Other chains verify PQ signatures by querying this registry via Warp.

Precompiles

| Address | Function | Gas |

|---|---|---|

| 0x0300...01 | Dilithium-3 signature verification | 15,000 |

| 0x0300...02 | Kyber-768 key encapsulation | 10,000 |

| 0x0300...03 | Kyber-768 decapsulation | 10,000 |

| 0x0300...04 | NTT forward transform | 5,000 |

| 0x0300...05 | NTT inverse transform | 5,000 |

Migration Path

Users transition to PQ security:

1. Register ML-DSA key on Q-chain, linked to existing ECDSA address

2. Set PQ key as backup signer for multi-sig wallets

3. When ECDSA is deprecated (quantum threat timeline), switch to Q-chain signing exclusively

Security Considerations

1. Key size: Dilithium-3 keys are large (1952 bytes public, 3293 bytes signature). Block size limits account for this.

2. Hybrid period: during transition, both ECDSA and ML-DSA signatures are accepted. A compromised ECDSA key cannot override a PQ-signed transaction if PQ is registered.

3. Parameter agility: the Q-chain VM can be upgraded to new PQ standards (e.g., if NIST revises parameters) via L1 governance.

Reference

| Resource | Location |

|---|---|

| Quantum VM | github.com/luxfi/node/vms/qvm/ |

| ML-DSA implementation | github.com/luxfi/node/crypto/dilithium/ |

| ML-KEM implementation | github.com/luxfi/node/crypto/kyber/ |

| NTT acceleration | LP-029 |

Copyright

Licensed under the MIT License.