utxo/LLM.md

luxfi/utxo

Overview

Go module: github.com/luxfi/utxo

The UTXO library + signature Fx plugin system for Lux X-Chain. Each Fx plugin implements one signature scheme. X-Chain consensus dispatches by Fx ID — any registered curve can spend UTXOs.

X-Chain = Universal Multi-Curve Settlement Layer

X-Chain supports multiple signature schemes simultaneously. This lets anyone from any ecosystem settle value natively by signing with their own curve. No bridge contracts, no wrapped tokens.

Fx Plugin Roadmap

Package	Scheme	Use Case	Status
secp256k1fx	secp256k1 ECDSA	Ethereum, Bitcoin, Cosmos	✓ complete
nftfx	NFT extension	Non-fungible tokens	✓ complete
propertyfx	Property attestations	Attestation outputs	✓ complete
mldsafx	ML-DSA-65 (FIPS 204)	PQ single-signer, Lux native	complete
slhdsafx	SLH-DSA-SHA2-192f (FIPS 205)	Hash-based PQ, treasury/governance	complete
ed25519fx	Ed25519	Solana, Cardano, NEAR, Polkadot	complete
secp256r1fx	P-256 (NIST secp256r1)	Apple Secure Enclave, WebAuthn, TPM	complete
sr25519fx	Sr25519 Schnorr	Polkadot/Substrate	TODO
schnorrfx	BIP-340 Schnorr	Bitcoin Taproot	TODO
cggmp21fx	CGGMP21 threshold ECDSA	Verify classical threshold sigs (MPC custody)	TODO
frostfx	FROST threshold Schnorr	Verify Bitcoin Taproot threshold sigs	TODO
coronafx	Corona threshold (PQ)	Verify PQ threshold sigs from M-Chain (LP-134)	TODO
ringfx	LSAG ring signatures	Sender anonymity (Monero-style)	TODO
kemfx	ML-KEM-768	Stealth addresses, encrypted memos	TODO

Threshold signing architecture: X-Chain Fx plugins VERIFY threshold signatures. The actual threshold signing ceremonies happen on M-Chain — the MPC runtime carved out of the legacy T-Chain monolith per LP-134 (Lux Chain Topology). So cggmp21fx/frostfx/coronafx are verifier plugins that accept the final aggregated sig — the keygen + signing rounds run as ceremonies on M-Chain via chains/thresholdvm in MPC mode. The legacy "T-Chain" name now refers only to teleportvm (LP-6332), which is unrelated.

Not implementing: thresholdmldsafx (threshold ML-DSA). No FIPS standard exists yet. Use coronafx for PQ threshold signing — Corona is the real standardized PQ threshold primitive.

Fx Interface

type Fx interface {
    Initialize(vm interface{}) error
    VerifyTransfer(tx, in, cred, utxo) error
    VerifyCredentials(tx, in, cred) error
    VerifyPermission(tx, in, cred, owner) error
}

Each Fx implements signature verification for its scheme. A transaction's Credentials field carries per-input signatures; X-Chain dispatches by the Fx ID attached to each output's owner type.

Mixed-Curve Multisig

A single UTXO's OutputOwners can reference pubkeys from different Fx plugins. Examples:

• 2-of-3: Ed25519 (user) + ML-DSA (backup) + SLH-DSA (cold storage)
• Time-locked recovery: secp256k1 (primary) OR ML-DSA after timelock
• Cross-ecosystem multisig: Solana Ed25519 + Ethereum secp256k1 jointly control a UTXO

Structure

utxo/
├── addresses.go
├── api.go
├── asset.go
├── atomic_utxo_manager.go
├── atomic_utxos.go
├── base_tx.go
├── context.go
├── flow_checker.go
├── lux.go
├── metadata.go
├── secp256k1fx/      ✓ classical ECDSA (secp256k1)
├── nftfx/            ✓ NFTs
├── propertyfx/       ✓ attestations
├── mldsafx/          ✓ ML-DSA-65 PQ signing (FIPS 204)
├── slhdsafx/         ✓ SLH-DSA hash-based PQ (FIPS 205)
├── ed25519fx/        ✓ Ed25519 (Solana/Cardano/NEAR/Polkadot)
└── secp256r1fx/      ✓ P-256 ECDSA (WebAuthn/Secure Enclave/TPM)

Related

• ~/work/lux/crypto/ — PQ primitives (ML-DSA, SLH-DSA, ML-KEM, Corona, etc.)
• ~/work/lux/precompile/ — EVM precompiles that wrap each Fx's verifier so C-Chain contracts can verify any curve
• ~/work/lux/node/vms/xvm/ — X-Chain VM that consumes these Fx plugins
• ~/work/lux/papers/lp-105-quasar-consensus.tex — Quasar three-layer consensus