STAGE 5 · MASTERLEVEL · Advanced6 LESSONSABOUT 36 MINLIGHTNING & LAYERS
The intermediate course explained Lightning from the outside. This one opens the channel. Six lessons, about 45 minutes, for people who want to know exactly what they are trusting when they tap Send.
BY THE END OF THIS COURSE YOU WILL BE ABLE TO
- Draw the transactions behind a channel and explain the penalty
- Trace an HTLC through three hops
- Explain how a sender finds a route and why payments fail
- Read a BOLT 11 invoice and a BOLT 12 offer
- Describe splicing, swaps, watchtowers and PTLCs
Every lesson ends with a quiz or a challenge; the course is complete when each lesson is.
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LESSONS
01Channel state and the penaltyEach channel state is a pre-signed commitment transaction. Updating means signing a new one and revoking the old by sharing a secret that lets the partner punish any attempt to use it.✓ quiz7 MIN✓02HTLCs, step by stepA hashed timelock contract pays whoever reveals a secret before a deadline, or refunds after. Chaining them with decreasing deadlines lets payments cross strangers safely.✓ quiz⚡ challenge7 MIN✓03Onion routing and pathfindingSenders build routes from a gossiped channel graph and wrap each payment in layers of encryption. Balances are private, so payments probe and retry; multipath splits big ones.✓ quiz6 MIN✓04Invoices, offers and addressesBOLT 11 invoices are one-time, signed requests. BOLT 12 offers are reusable and fetch invoices privately. LNURL and Lightning addresses add convenience through a web server.✓ quiz5 MIN✓05Splicing, swaps and liquidity adsSubmarine swaps move value between chain and Lightning trustlessly. Splicing resizes an open channel in place. Dual funding and liquidity ads solve the inbound problem at open.✓ quiz5 MIN✓06Watchtowers, PTLCs and what comes nextWatchtowers guard channels while you sleep. PTLCs fix routing privacy, Taproot channels cut costs, and Eltoo would replace penalties with a simpler update rule if a soft fork allows it.✓ quiz6 MIN✓