From: Rusty Russell <rusty@rustcorp•com.au>
To: Anthony Towns <aj@erisian•com.au>, bitcoin-dev@lists•linuxfoundation.org
Cc: lightning-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] [Lightning-dev] More thoughts on NOINPUT safety
Date: Wed, 20 Mar 2019 10:52:05 +1030 [thread overview]
Message-ID: <87k1gubdjm.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20190313014143.ifffshwdux2jt7w5@erisian.com.au>
Anthony Towns <aj@erisian•com.au> writes:
> If you publish to the blockchain:
...
> 4 can be dropped, state 5 and finish can be altered). Since the CSV delay
> is chosen by the participants, the above is still a possible scenario
> in eltoo, though, and it means there's some risk for someone accepting
> bitcoins that result from a non-cooperative close of an eltoo channel.
AJ, this was a meandering random walk which shed very little light.
I don't find the differentiation between malicious and non-malicious
double-spends convincing. Even if you trust A, you already have to
worry about person-who-sent-the-coins-to-A. This expands that set to be
"miner who mined coins sent-to-A", but it's very hard to see what
difference that makes to how you'd handle coins from A.
> Beyond that, I think NOINPUT has two fundamental ways to cause problems
> for the people doing NOINPUT sigs:
>
> 1) your signature gets applied to a unexpectedly different
> script, perhaps making it look like you've being dealing
> with some blacklisted entity. OP_MASK and similar solves
> this.
... followed by two paragraphs describing how it's not a "fundamental
way to cause problems" that you (or I) can see.
> For the second case, that seems a little more concerning. The nightmare
> scenario is maybe something like:
>
> * naive users do silly things with NOINPUT signatures, and end up
> losing funds due to replays like the above
As we've never seen with SIGHASH_NONE?
> * initial source of funds was some major exchange, who decide it's
> cheaper to refund the lost funds than deal with the customer complaints
>
> * the lost funds end up costing enough that major exchanges just outright
> ban sending funds to any address capable of NOINPUT, which also bans
> all taproot/schnorr addresses
I don't find this remotely credible.
> FWIW, I don't have a strong opinion here yet, but:
>
> - I'm still inclined to err on the side of putting more safety
> measures in for NOINPUT, rather than fewer
In theory, sure. But not feel-good and complex "safety measures" which
don't actually help in practical failure scenarios.
> - the "must have a sig that commits to the input tx" seems like it
> should be pretty safe, not too expensive, and keeps taproot's privacy
> benefits in the cases where you end up needing to use NOINPUT
If this is considered necessary, can it be a standardness rule rather
than consensus?
Thanks,
Rusty.
next prev parent reply other threads:[~2019-03-20 0:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-13 1:41 [bitcoin-dev] " Anthony Towns
2019-03-13 6:41 ` [bitcoin-dev] [Lightning-dev] " ZmnSCPxj
2019-03-13 11:10 ` Anthony Towns
2019-03-14 5:22 ` ZmnSCPxj
2019-03-14 7:24 ` Anthony Towns
2019-03-14 7:55 ` ZmnSCPxj
2019-03-14 12:00 ` Christian Decker
2019-03-20 0:22 ` Rusty Russell [this message]
2019-03-20 3:33 ` Rusty Russell
2019-03-20 7:38 ` ZmnSCPxj
2019-03-20 8:07 ` ZmnSCPxj
2019-03-21 8:37 ` Johnson Lau
2019-03-21 9:06 ` Anthony Towns
2019-03-21 10:05 ` ZmnSCPxj
2019-03-21 11:55 ` Anthony Towns
2019-03-22 1:59 ` ZmnSCPxj
2019-03-22 2:58 ` Anthony Towns
2019-03-22 7:46 ` ZmnSCPxj
2019-03-22 4:23 ` Johnson Lau
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