Electrum is a mature, production-grade Bitcoin wallet with full Lightning Network support, used by thousands of users daily. It is a desktop/mobile application with a daemon architecture, offering three GUI frontends: a full-featured PyQt6 desktop interface, a Qt Quick (QML) mobile interface, and a curses terminal interface. The daemon manages wallet lifecycle, network connections, and exposes a JSON-RPC API. The codebase is highly modular, with a plugin system for hardware wallets (Trezor, Ledger, Coldcard, KeepKey, Jade, BitBox02, Safe-T, Digital Bitbox), label sync, two-factor authentication, submarine swaps, watchtowers, and more. Core features include SPV (Simple Payment Verification) with merkle proof validation, coin selection with privacy-aware heuristics (CoinChooserPrivacy), BIP32 key derivation, mnemonic seeds (BIP39, SLIP39, legacy), and a full Lightning Network implementation with pathfinding (LNPathFinder using Dijkstra with liquidity hints), channel management, HTLC accounting, trampoline routing, and onion messages. The repository also includes deterministic build scripts for Linux (AppImage), Windows (Wine+PyInstaller), macOS, and Android (python-for-android), with reproducible builds using pinned dependencies and hash verification.
Lightning Network Daemon (lnd) is a full-featured Lightning Network node implementation written in Go. It enables users to participate in the Lightning Network by opening and managing payment channels, sending/receiving payments, routing payments for others, and enforcing channel contracts via blockchain monitoring. The architecture is modular, separating concerns into distinct subsystems: peer-to-peer networking (brontide, lnpeer), channel state management (channeldb, chanstate, lnwallet), payment switching and routing (htlcswitch, routing), blockchain monitoring (chainntnfs), contract enforcement (contractcourt), RPC services (lnrpc), watchtower functionality, and autopilot for automated channel management. Key entry points include the daemon (cmd/lnd/main.go), CLI (cmd/lncli/main.go), and various RPC servers. Data flows involve processing peer messages to update channel state, persisting state to pluggable backends (BoltDB, PostgreSQL, SQLite, etcd), monitoring blockchain events affecting channels, and handling RPC commands for node control and queries. External dependencies include Bitcoin full nodes (bitcoind/btcd or Neutrino), database libraries, and various Go utilities (btcutil, btcec, gRPC).
This repository is a production-grade Go library implementing a Bitcoin light client based on BIP 157/158 compact block filters (Neutrino). It is designed for mobile Lightning Network wallets and provides SPV (Simplified Payment Verification) without requiring a full node. The core architecture revolves around a ChainService that orchestrates peer connections, block header sync, filter header sync, UTXO queries, transaction broadcasting, and chain rescanning. The library stores headers in flat files with bbolt-backed indices, and filters in a boltdb database. It includes a sophisticated peer query management system with retry, timeout, and banning logic, as well as caching layers for blocks and filters. The codebase is well-structured into subpackages with clear responsibilities, many of which are reusable in other Go projects. It is actively maintained by Lightning Labs and used in production by lnd (Lightning Network Daemon).