📅 Original date posted:2018-05-01
📝 Original message:Jim Posen <jim.posen at gmail.com> writes:
> Can you explain why a fixed offset along the whole circuit is enough to
> ensure safely as opposed to an increased delta at each hop?
Sure. Let's assume we have chosen a path `A->B->C->D->E`. For simplicity
let's assume they all have a CLTV delta of 144 blocks (lnd's default
setting). Furthermore let's assume that the CSV timeout for the channels
is also 144.
This means that with the current LN-penalty mechanism you'd have the
following CLTV deltas in the HTLC:
```
A -(576)-> B -(432)-> C -(288)-> D -(144)-> E
```
Meaning that if the current time is approaching the absolute CLTV we
need initiate a channel closure to safely fetch the preimage on-chain,
and be able to turn around and send it on the upstream channel.
This is minimal, but can be arbitrarily higher, if you follow the best
practice of obfuscating the final destination by building a shadow route
behind the real recipient, and add it's CLTV deltas and fees to your
route.
With eltoo you'd need to make sure that you have the settlement
transaction confirmed before your desired CLTV timeout delta begins to
count down. So if the CLTV of the HTLC is `now + CSV timeout + CLTV
delta` you need to initiate a close, whereas Lightning allows you to
wait for time `now + CLTV delta`. Effectively this results in the
following time deltas:
```
A -(576+144)-> B -(432+144)-> C -(288+144)-> D -(144+144)-> E
```
Taking the last hop for example, if we had a CLTV of 1000 with eltoo
we'd need to start closing at height 712, instead of 856 with
LN-penalty. However, this increased delta does not accumulate along the
path, it's just a fixed offset. The longer the route, the smaller the
actual impact of this offset.
Christian Decker [ARCHIVE] /
npub1wt…gtuyn
2023-06-07 18:11:45
in reply to nevent1q…8nad
Author Public Key
npub1wtx5qvewc7pd6znlvwktq03mdld05mv3h5dkzfwd3dc30gdmsptsugtuynPublished at
2023-06-07 18:11:45Event JSON
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"content": "📅 Original date posted:2018-05-01\n📝 Original message:Jim Posen \u003cjim.posen at gmail.com\u003e writes:\n\u003e Can you explain why a fixed offset along the whole circuit is enough to\n\u003e ensure safely as opposed to an increased delta at each hop?\n\nSure. Let's assume we have chosen a path `A-\u003eB-\u003eC-\u003eD-\u003eE`. For simplicity\nlet's assume they all have a CLTV delta of 144 blocks (lnd's default\nsetting). Furthermore let's assume that the CSV timeout for the channels\nis also 144.\n\nThis means that with the current LN-penalty mechanism you'd have the\nfollowing CLTV deltas in the HTLC:\n\n```\nA -(576)-\u003e B -(432)-\u003e C -(288)-\u003e D -(144)-\u003e E\n```\n\nMeaning that if the current time is approaching the absolute CLTV we\nneed initiate a channel closure to safely fetch the preimage on-chain,\nand be able to turn around and send it on the upstream channel.\n\nThis is minimal, but can be arbitrarily higher, if you follow the best\npractice of obfuscating the final destination by building a shadow route\nbehind the real recipient, and add it's CLTV deltas and fees to your\nroute.\n\nWith eltoo you'd need to make sure that you have the settlement\ntransaction confirmed before your desired CLTV timeout delta begins to\ncount down. So if the CLTV of the HTLC is `now + CSV timeout + CLTV\ndelta` you need to initiate a close, whereas Lightning allows you to\nwait for time `now + CLTV delta`. Effectively this results in the\nfollowing time deltas:\n\n```\nA -(576+144)-\u003e B -(432+144)-\u003e C -(288+144)-\u003e D -(144+144)-\u003e E\n```\n\nTaking the last hop for example, if we had a CLTV of 1000 with eltoo\nwe'd need to start closing at height 712, instead of 856 with\nLN-penalty. However, this increased delta does not accumulate along the\npath, it's just a fixed offset. The longer the route, the smaller the\nactual impact of this offset.",
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