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In a given lightning channel what are the risks of allowing the remote node to be offline for an extended period of time?

The obvious being the funds in the channel would be inaccessible, but if we have a long time preference and aren't really worried about that, are there any risks that they could cheat the channel setup while offline?

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You only need be concerned about your own uptime. If your counterparty is offline for extended periods, they are at risk of being cheated by you, but it does not put you at risk.

However, since forwarding payments on the shared channel requires both parties to be online, their being offline incurs an opportunity cost onto you due to your balance in that channel lying fallow without generating fees. As @sr_gi notes below, a peer that is frequently offline may also hamper your ability to use the Lightning Network at all, if they are one of your main connections to the wider network.

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    I´ll add that, if they are your single point of entry to LN, you'd effectively be forced to open another channel if you want to continue using the system, which may become an issue in high onchain fee periods. Therefore, them being offline can be sort of a DoS attack on you.
    – sr_gi
    Commented May 24, 2023 at 3:05
  • Good point @sr_gi nodes with low centrality or just few channels would be affected by this.
    – Poseidon
    Commented May 24, 2023 at 7:23
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I'm not sure what you mean by the "remote channel". If you don't control the channel and you grant full access to a third party to manage your Lightning node/channel then the worst they can do is spend all the Bitcoin in that channel and push the total capacity to the counterparty's balance in the channel. You can effectively lose all the Bitcoin you initially locked up in the channel.

Assuming you control the channel, if funds are moving back and forth in the channel the Lightning security model relies on observing the blockchain in case your counterparty tries to cheat you by posting a revoked state. If you don't do this or stay offline for a sustained period you may miss the cheat attempt and hence fail to respond within the required time window by broadcasting the justice transaction. The amount of Bitcoin you lose will be the difference between your current balance in the channel and the balance you had in the revoked state.

If you are a routing node and not just an edge node then being offline for a sustained period could also result in you not earning routing fees you could have earned in that time. Other Lightning nodes may choose to close channels with you as you have potentially cost them routing fees in the time that you've been offline. Rather than revealing the preimage to the hash of the HTLC in a timely fashion you may have locked up capital across the route, prevented Lightning nodes from routing other payments and ultimately require them to close channels. As a routing node you should really aim for 100 percent uptime. As an edge node you are just hurting yourself if you are offline for a sustained period as you can't receive payments and you are giving your counterparty the opportunity to cheat you.

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  • my mistake I meant remote node not remote channel, I corrected it
    – Poseidon
    Commented May 23, 2023 at 8:55
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    @Poseidon: "Assuming we do not control the remote node in a given lightning channel" Assuming we don't control both nodes in a channel? Why would we open a channel with ourselves?
    – Michael Folkson
    Commented May 23, 2023 at 16:20
  • There might not be a good reason to do so, but in case there was I wanted to make it clear this was not the case.
    – Poseidon
    Commented May 23, 2023 at 20:23

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