Christian Decker [ARCHIVE] on Nostr: 📅 Original date posted:2020-10-13 📝 Original message: I think the mechanism can ...
📅 Original date posted:2020-10-13
📝 Original message:
I think the mechanism can indeed create interesting dynamics, but not in
a good sense :-)
>> I can still establish channels to various low-reputation nodes, and
>> then use them to grief a high-reputation node. Not only do I get to
>> jam up the high-reputation channels, as a bonus I get the
>> low-reputation nodes to pay for it!
>
> So you're saying:
>
> ATTACKER --(no hold fee)--> LOW-REP --(hold fee)--> HIGH-REP
>
> If I were LOW-REP, I'd still charge an unknown node a hold fee. I
> would only waive the hold fee for high-reputation nodes. In that case,
> the attacker is still paying for the attack. I may be forced to take a
> small loss on the difference, but at least the larger part of the pain
> is felt by the attacker. The assumption is that this is sufficient
> enough to deter the attacker from even trying.
The LOW-REP node being out of pocket is the clue here: if one party
loses funds, even a tiny bit, another party gains some funds. In this
case the HIGH-REP node collaborating with the ATTACKER can extract some
funds from the intermediate node, allowing them to dime their way to all
of LOW-REP's funds. If an attack results in even a tiny loss for an
intermediary and can be repeated, the intermediary's funds can be
syphoned by an attacker.
Another attack that is a spin on ZmnSCPxj's waiting to backpropagate the
preimage is even worse:
- Attacker node `A` charging hold fees receives HTLC from victim `V`
- `A` does not forward the HTLC, but starts charging hold fees
- Just before the timeout for the HTLC would force us to settle onchain
`A` just removes the HTLC without forwarding it or he can try to
forward at the last moment, potentially blaming someone else for its
failure to complete
This results in `A` extracting the maximum hold fee from `V`, without
the downstream hold fees cutting into their profits. By forwarding as
late as possible `A` can cause a downstream failure and look innocent,
and the overall payment has the worst possible outcome: we waited an
eternity for what turns out to be a failed attempt.
Cheers,
Christian
📝 Original message:
I think the mechanism can indeed create interesting dynamics, but not in
a good sense :-)
>> I can still establish channels to various low-reputation nodes, and
>> then use them to grief a high-reputation node. Not only do I get to
>> jam up the high-reputation channels, as a bonus I get the
>> low-reputation nodes to pay for it!
>
> So you're saying:
>
> ATTACKER --(no hold fee)--> LOW-REP --(hold fee)--> HIGH-REP
>
> If I were LOW-REP, I'd still charge an unknown node a hold fee. I
> would only waive the hold fee for high-reputation nodes. In that case,
> the attacker is still paying for the attack. I may be forced to take a
> small loss on the difference, but at least the larger part of the pain
> is felt by the attacker. The assumption is that this is sufficient
> enough to deter the attacker from even trying.
The LOW-REP node being out of pocket is the clue here: if one party
loses funds, even a tiny bit, another party gains some funds. In this
case the HIGH-REP node collaborating with the ATTACKER can extract some
funds from the intermediate node, allowing them to dime their way to all
of LOW-REP's funds. If an attack results in even a tiny loss for an
intermediary and can be repeated, the intermediary's funds can be
syphoned by an attacker.
Another attack that is a spin on ZmnSCPxj's waiting to backpropagate the
preimage is even worse:
- Attacker node `A` charging hold fees receives HTLC from victim `V`
- `A` does not forward the HTLC, but starts charging hold fees
- Just before the timeout for the HTLC would force us to settle onchain
`A` just removes the HTLC without forwarding it or he can try to
forward at the last moment, potentially blaming someone else for its
failure to complete
This results in `A` extracting the maximum hold fee from `V`, without
the downstream hold fees cutting into their profits. By forwarding as
late as possible `A` can cause a downstream failure and look innocent,
and the overall payment has the worst possible outcome: we waited an
eternity for what turns out to be a failed attempt.
Cheers,
Christian