lightning-security-module

Lightning Security Module (Remote Signer)

Set up an lnd remote signer container that holds private keys on a separate, secured machine. The signer never routes payments or opens channels — it only holds keys and signs when asked by a watch-only litd node.

Architecture

Agent Machine                     Signer Machine (secure)
┌─────────────────┐              ┌─────────────────────┐
│  litd (watch-only)│◄──gRPC───►│  lnd (signer)        │
│  - neutrino      │             │  - holds seed         │
│  - manages chans │             │  - signs commitments  │
│  - routes pmts   │             │  - signs on-chain txs │
│  - NO key material│            │  - no p2p networking   │
└─────────────────┘              └─────────────────────┘

The watch-only node handles all networking and channel management. The signer node holds the seed and performs cryptographic signing. Even if the agent machine is fully compromised, the attacker cannot extract private keys.

See references/architecture.md for the full architecture explainer.

Quick Start (Container — Recommended)

On the Signer Machine

# 1. Install lnd signer image
skills/lightning-security-module/scripts/install.sh

# 2. Start signer container
skills/lightning-security-module/scripts/start-signer.sh

# 3. Set up signer wallet and export credentials
skills/lightning-security-module/scripts/setup-signer.sh

# 4. Copy the credentials bundle to the agent machine
#    The setup script prints the bundle path and base64 string.

On the Agent Machine

# 5. Import credentials bundle
skills/lnd/scripts/import-credentials.sh --bundle <credentials-bundle>

# 6. Start litd in watch-only mode
skills/lnd/scripts/start-lnd.sh --watchonly

# 7. Create watch-only wallet
skills/lnd/scripts/create-wallet.sh

# 8. Check status
skills/lnd/scripts/lncli.sh getinfo

Two-Container Local Setup

For testing both on the same machine:

# Start litd + signer together
skills/lnd/scripts/start-lnd.sh --watchonly

# Set up signer wallet
skills/lightning-security-module/scripts/setup-signer.sh --container litd-signer

# Import credentials and create watch-only wallet
skills/lnd/scripts/import-credentials.sh --bundle ~/.lnget/signer/credentials-bundle
skills/lnd/scripts/create-wallet.sh --container litd

Installation

Default: pulls the lnd Docker image for the signer.

skills/lightning-security-module/scripts/install.sh

This pulls lightninglabs/lnd:v0.20.0-beta from Docker Hub. The signer only needs plain lnd (not litd) since it only holds keys and signs.

Build from Source (Fallback)

skills/lightning-security-module/scripts/install.sh --source

Native Mode

For running the signer without Docker:

# Set up signer natively
skills/lightning-security-module/scripts/setup-signer.sh --native

# Start signer natively
skills/lightning-security-module/scripts/start-signer.sh --native

# Stop signer natively
skills/lightning-security-module/scripts/stop-signer.sh --native

Remote Nodes

Export credentials from a remote signer:

skills/lightning-security-module/scripts/export-credentials.sh \
    --rpcserver signer-host:10012 \
    --tlscertpath ~/signer-tls.cert \
    --macaroonpath ~/signer-admin.macaroon

Credential Bundle Format

The exported bundle (~/.lnget/signer/credentials-bundle/) contains:

File	Purpose
accounts.json	Account xpubs for watch-only wallet import
tls.cert	Signer's TLS certificate for authenticated gRPC
admin.macaroon	Signer's admin macaroon for RPC authentication

The bundle is also available as a single base64-encoded tar.gz file (credentials-bundle.tar.gz.b64) for easy copy-paste transfer between machines.

Scripts

Script	Purpose
install.sh	Pull lnd signer image (or build from source)
docker-start.sh	Start signer container
docker-stop.sh	Stop signer container
setup-signer.sh	Create signer wallet and export credentials
start-signer.sh	Start signer (delegates to Docker by default)
stop-signer.sh	Stop signer (delegates to Docker by default)
export-credentials.sh	Re-export credentials from running signer

Managing the Signer

Start

# Docker (default)
skills/lightning-security-module/scripts/start-signer.sh

# With network override
skills/lightning-security-module/scripts/start-signer.sh --network mainnet

Stop

# Docker stop (preserve data)
skills/lightning-security-module/scripts/stop-signer.sh

# Docker stop + remove volumes
skills/lightning-security-module/scripts/stop-signer.sh --clean

Re-export Credentials

If TLS certificates or macaroons have been regenerated:

skills/lightning-security-module/scripts/export-credentials.sh

Configuration

Container Config

The signer compose template is at skills/lightning-security-module/templates/docker-compose-signer.yml. Config is passed via command-line arguments.

Native Config

The native signer config template is at skills/lightning-security-module/templates/signer-lnd.conf.template. Key differences from a standard lnd node:

• No P2P listening (--listen=) — signer doesn't route
• RPC on 0.0.0.0:10012 — accepts connections from watch-only node
• REST on localhost:10013 — local only, for wallet creation
• TLS extra IP 0.0.0.0 — watch-only on a different machine can connect
• No autopilot, no routing fees — signer is signing-only

Security Model

What stays on the signer:

• 24-word seed mnemonic
• All private keys (funding, revocation, HTLC)
• Wallet database with key material

What gets exported:

• Account xpubs (public keys only — cannot spend)
• TLS certificate (for authenticated connection)
• Admin macaroon (for RPC auth — scope down for production)

Threat model:

• Compromised agent machine cannot sign transactions or extract keys
• Attacker with agent access can see balances and channel state but not spend
• Signer machine should have minimal attack surface

Production hardening:

• Replace admin macaroon with a signer-only macaroon (see macaroon-bakery)
• Restrict signer RPC to specific IP addresses via firewall
• Run signer on dedicated hardware or a hardened VM
• Use Lightning Node Connect (LNC) via lightning-mcp-server for read-only agent access

Macaroon Bakery for Signer

For production, bake a signing-only macaroon:

skills/macaroon-bakery/scripts/bake.sh --role signer-only \
    --container litd-signer --rpc-port 10012

Then re-export the credentials bundle with the scoped macaroon.

Container & Ports

Container	Purpose	Ports
litd-signer	Remote signer (lnd)	10012, 10013

Port	Service	Interface	Description
10012	gRPC	0.0.0.0	Signer RPC (watch-only connects here)
10013	REST	0.0.0.0	REST for wallet creation

File Locations

Path	Purpose
~/.lnget/signer/wallet-password.txt	Signer wallet passphrase (0600)
~/.lnget/signer/seed.txt	Signer seed mnemonic (0600)
~/.lnget/signer/credentials-bundle/	Exported credentials
~/.lnget/signer/signer-lnd.conf	Signer config (native mode)
versions.env	Pinned container image versions