LP-0074Finalpost-quantumfalconntrulatticeprecompile

LP-074: FALCON Signature EVM Precompile

Abstract

Defines an EVM precompile at 0x0074 for FALCON signature verification. FALCON (Fast-Fourier Lattice-based Compact Signatures over NTRU) produces the smallest post-quantum signatures among lattice schemes (666 bytes at NIST Level 1). It is selected for use cases where signature size is critical: on-chain attestations, certificate chains, and compact proofs.

Specification

Parameter Sets

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

| FALCON-512 | 1 | 897 B | 666 B | 128-bit |

| FALCON-1024 | 5 | 1,793 B | 1,280 B | 256-bit |

Precompile

Address: 0x0074


Input:  (bytes32 messageHash, bytes signature, bytes publicKey, uint8 paramSet)
Output: bytes32 (0x01 valid, 0x00 invalid)
Gas:    65,000 (FALCON-512), 130,000 (FALCON-1024)

Comparison with ML-DSA

| Property | FALCON-512 | ML-DSA-44 |

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

| Signature size | 666 B | 2,420 B |

| Public key size | 897 B | 1,312 B |

| Sign time | 8.2ms | 0.3ms |

| Verify time | 0.1ms | 0.2ms |

| Gas cost | 65,000 | 80,000 |

FALCON wins on size; ML-DSA wins on signing speed. FALCON signing requires floating-point discrete Gaussian sampling, making constant-time implementation harder.

Use Cases

| Application | Rationale |

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

| Certificate chains | Compact signatures reduce chain size |

| On-chain attestations | Lower calldata cost (EIP-4844 blob pricing) |

| Compressed proofs | Aggregate attestation with minimal on-chain footprint |

Security Considerations

1. FALCON security relies on the NTRU lattice assumption and Short Integer Solution (SIS).

2. Signing requires careful floating-point sampling. Side-channel hardened implementation is mandatory.

3. FALCON is a NIST PQC finalist (Round 4 alternate) but not yet a FIPS standard. Use ML-DSA (FIPS 204) for FIPS-mandated contexts.

4. Key generation is slower than ML-DSA (~100ms vs ~1ms). Pregenerate keys in KMS.

Reference

| Resource | Location |

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

| FALCON precompile | github.com/luxfi/evm/precompile/contracts/falcon.go |

| FALCON library | github.com/luxfi/crypto/falcon/ |

| FALCON specification | https://falcon-sign.info |

Copyright

Licensed under the MIT License.