Lightning Specification Meeting 2024/08/26

[t-bast]

The meeting will take place on Monday 2024/08/26 at 8pm UTC (5:30am Adelaide time) on Libera Chat IRC #lightning-dev. It is open to the public.

A video link is available for higher bandwidth communication: https://meet.jit.si/Lightning-Spec-Meeting

Recently Updated Proposals / Seeking Review

This section contains changes that have been opened or updated recently and need feedback from the meeting participants.

• Offers Offers #798
• Channel jamming draft: HTLC Endorsement to Mitigate Channel Jamming #1071
• Taproot extension-bolt: simple taproot channels (feature 80/81) #995
• Taproot gossip extension-bolt: taproot gossip (features 32/33) #1059
• Liquidity ads option_will_fund: liquidity ads #878 Extensible Liquidity Ads #1153
• Splicing Splice draft (feature 62/63) #863 Channel Splicing (feature 62/63) #1160
• Async payments Support async payments in BOLT 12 #1149
• Dynamic Commitments Extension/dynamic commitments #1117 vs Upgrade on Reestablish BOLT 2: upgrade protocol on reestablish #868
• gossip_status BOLT 7: gossip_status (feature 66/67) #1186
• Peer storage backup Peer backup storage (feature 40/41/42/43) #881 or Peer storage for nodes to distribute small encrypted blobs. #1110
• Bolt 12 contacts / mutual message auth: https://delvingbitcoin.org/t/bolt-12-trusted-contacts/1046
• Attributable errors Attributable errors (feature 36/37) #1044
• Clarify channel_reestablish requirements Clarify channel_reestablish requirements #1049 or Rework channel_reestablish requirements #1051

Stale Proposals

This section contains pending changes that may not need feedback from the meeting participants, unless someone explicitly asks for it during the meeting. These changes are usually waiting for implementation work to happen to drive more feedback.

• Inbound fees Inbound routing fees blips#18 and Add a bLIP for backwards-compatible inbound fees blips#22

Waiting for interop

This section contains changes that have been conceptually ACKed and are waiting for at least two implementations to fully interoperate.
They most likely don't need to be covered during the meeting, unless someone asks for updates.

• Simplified mutual close option_simple_close (features 60/61) #1096
• Trampoline routing Trampoline Routing (2021 edition) (Feature 56/57) #829 and Trampoline onion format (Feature 56/57) #836
• Zero reserve Add option_zero_reserve (FEATURE 64/65) #1140 (follow-up on bolt2: relax channel_reserve_satoshis requirements #1133 to include a feature bit)
• Don't force close until error is received after channel_reestablish Nodes shouldn't publish their commitment when receiving outdated channel_reestablish #934

Long Term Updates

This section contains long-term changes that need review, but require a substantial implementation effort.

• Simplified commitment Feature 106/107: option_simplified_update. #867
• lnprototest (https://github.com/rustyrussell/lnprototest)

[Roasbeef]

channel jamming:

• new attack variant discovered by morehouse
• working on updating to account for it

taproot chans:

• got some review from fabrice, roasbeef working on the changes
• still not updated to use the mini script compatible scripts, will do that in the non-staging bit
• rbf co-op:
  • lnd still needing to make change for locktime instead of sequence

taproot gossip:

• close to revival...
  • near term goal to remove from draft state
  • lnd continuing to work on the new code path

bolt12 contacts:

• delving post up, not much progress after the initial discussion

splicing:

• CLN working thru set of changes to

async payments + trampoline:

• rn trampoline node gets a blinded paths, and relays to blinded paths
  • the issue is that you aren't forced to use it in a privacy safe way
  • so then can use zero hop blinded paths w/ the node themselves
  • so receivers can make bad blinded paths, revealing more information to the sender's first hop
• potential work around:
  • add another trampoline hop
  • essentially requires including the blinded path twice
    • may only be an issue if you do trampoline "all the way"
    • so instead can do trampoline blinded hops?

dyn commits:

• pushed to slim down version, removing some of the funding output conversion
  • few segments that say note for reviewers, guide for reviewers, marking unstable parts
• while we're here....default anchors?
  • eclair stopped accepting non static key anchors
  • two changes:
    1. channel type negotiation by default
    2. reject all non-anchor channels
  • most nodes do support anchors these days

TRUC + v3 + 1p1c:

• what can we do w/ bitcoind 28 released?
• how does it affect the commitment format, etc?
• good topic for summit

peer storage back up:

• target for lnd 0.19
• interop:
  • does CLN have a full up to date impl?

inbound fees:

• lnd deployed bLIP that was proposed
  • discount only for now, RPC will reject anything that's positive

peer alternate connect:

• ability to privately connect out between peers
• diff from chan_ann: sent directly to a peer, not broadcasted to the broader network
• bridge to also allow diff pubkeys to be used for connection subsets:
  • brontide handshake mixes in the pubkey
  • so if you send another pubkey over an existing authenticated

nLightning:

• finished BOLT 11!
  • had some issues re signature computation
  • defaults to using the low r (not s?)
  • for LN it doesn't care if it's low or high r
  • having a hard time signing w/ low r
  • signature didn't match
  • realized that even post segwit, we use high r on the signature
  • related to: Always create signatures with Low R values bitcoin/bitcoin#13666
    • signature was wrong when using this
  • should add more test vectors that do include low r