Thread - Nostr Hypermedia

Matt Corallo matt@bitcoin.ninja 0 months ago

> I'd say you have the statechain model *until* you get the confirmation, then the model is closer to a DryjaPoon LSP than a statechain, until the expiration time. But yes, I agree the Ark model will be really interesting with channels on top, they are working on it since a while and it makes sense:

Blog - Ark Labs

Bitcoin Virtual Channels: Bringing Instant Settlement To Ark

Leveraging Ark’s VTXO paradigm, Virtual Channels enable efficient, low-cost Bitcoin payment channels by lifting smart contracts off-chain One of...

Yea depends a lot on how refresh happens and how much you transact. If you transact daily and refreshes are only once a month you’re effective always in the statechain world (at least until payment channels on top of Ark!). This is kinda my base case. If you’re more of a receive-only/savings wallet then it’s less trusted. Good luck explaining that to a user 😅. > I guess I'm playing with the word "unilateral" a bit here. I think that, realistically, the relevant thing is the exit against the coordinator, not against all the other users. The total cost of an unilateral exit in Ark is higher, but you can conceptually split it among more people in most failure modes. In a classic DryjaPoon, you share an UTxO among 2 users. That means that in best case scenarios (cooperative) the cost for opening/closing/resplicing would be X/2. In uncooperative scenarios, the cost for the exiting user is X. In an Ark with N users (ASP included), opening/closing/closing has a cost of about 10X, but that would be shared among N in cooperative cases, N-n in case n (most importantly including the ASP) are uncooperative. No, LN is still always cheaper (modulo on-chain HTLC resolution). In Ark even if everyone is exiting and splitting the cost (which isn’t quite how it works but let’s assume), the cost to exit is one-two transactions per wallet (average of one tree transaction plus one transaction to resolve their vTXO. You could do the resolution later so maybe it’s one but depends a lot on the specific construction). In LN it’s always only one. If you have any HTLCs pending you have to resolve them in LN, but I’m kinda assuming all the Ark things will mostly be used with HTLCs so you’d end up with the same in Ark.

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Replies (2)

Giacomo Zucco giacomozucco@primal.net 3 weeks ago

>No, LN is still always cheaper (modulo on-chain HTLC resolution). In Ark even if everyone is exiting and splitting the cost (which isn’t quite how it works but let’s assume), the cost to exit is one-two transactions per wallet (average of one tree transaction plus one transaction to resolve their vTXO. You could do the resolution later so maybe it’s one but depends a lot on the specific construction). In LN it’s always only one. I don't understand this. First, AFAIK unilateral exit in DryjaPoon always has 2 txs (otherwise you wouldn't have punishment), not one. Secondly, I'm assuming an economic push towards cooperating users just evicting non cooperative ones, so it's not even always 2 tx per "wallet", but potentially even as low as 2*logN/N txs, in optimistic cases where users just migrate to another ark where the current one is unresponsive. I know this is not how it works now, but I'm speaking about the potential evolution where high fees may push the system.

1 replies ↓

Matt Corallo matt@bitcoin.ninja 3 weeks ago

> I don't understand this. First, AFAIK unilateral exit in DryjaPoon always has 2 txs (otherwise you wouldn't have punishment), not one. It is two transactions to punish, yes, but if no punishment is required it’s only one. You then have an on-chain UTXO that can be spent like any other (and only by you), even though it isn’t a totally normal P2WPKH output. > Secondly, I'm assuming an economic push towards cooperating users just evicting non cooperative ones, so it's not even always 2 tx per "wallet", but potentially even as low as 2*logN/N txs, in optimistic cases where users just migrate to another ark where the current one is unresponsive. I know this is not how it works now, but I'm speaking about the potential evolution where high fees may push the system. An Ark can only be exited on-chain in one of two ways (and I’m not aware of any designs that would materially change this) - either the operator after a timeout or unrolling (at least part of[1]) the tree on-chain. Yes, you can roll your vTXO over inside the Ark system, but that just means the operator claims, and depends on collaboration with the operator [2]. If the operator is gone, you pay to dump the whole tree on chain, which is, basically, two transactions per user [3]. With a tree structure you can’t do better. [1] in theory each branch of an Ark tree could allow the operator to step in again, allowing one user to leave without forcing the entire unroll, but there’s still just two options for each leaf. [2] okay, you could trade your old-Ark vTXO for some new-Ark vTXO if the old-Ark operator went out of business, but now the new-Ark operator has to pay to unwind your old-Ark vTXO so you’re not getting out of the unwinding cost. [3] in case it’s not obvious, if you could all the intermediate nodes in a tree, you get N-1 (the second to last layer is N/2, the next layer up N/4…to 1, which sums to N-1). Yes I know you can make it an N-ary tree and reduce raw transaction count but you aren’t saving on output count.