How does the LN-Penalty mechanism currently leak out of the update layer?
Creating a channel
1.
What factors should be considered before opening a Lightning channel with a peer?
The Update Layer
1.
How would switching to PTLCs affect the update layer?
2.
If LN were to upgrade the update layer, would the network need to end-to-end upgrade?
3.
Why are the second stage HTLC transactions not part of the commitment transaction?
The Transfer Layer
1.
Explain how the timeout mechanism works for in-flight HTLCs?
2.
How is the payment hash sent to the payer?
3.
Can both HTLCs and PTLCs coexist in a channel?
4.
What's are the required parts of invoices?
The Multihop Layer
1.
How can nodes that are not always online prevent loss of funds?
2.
What are the risks of forwarding below-dust payments?
3.
What is the relationship of the revocation keys for multiple subsequent commitment transactions? What would change if revocation keys were independent?
4.
How can you send a payment to a node without getting an invoice? What are the tradeoffs of this payment method?
5.
Why is a grace period added to the HTLC timeout?
6.
What are routing hints and why are they important for private channels? Do they leak privacy?
Diffie–Hellman key exchange
1.
What is a Diffie-Hellman key exchange used for?
How and when do I use HMAC?
1.
What's the difference between a MAC and an HMAC?
2.
Where are HMAC and MAC implemented in lightning and why?