[Lightning-dev] lightning operation during / following a chain fork (e.g. BIP 50)

Benjamin Mord ben at mord.io
Tue Jan 30 16:26:36 UTC 2018


Thank you, ZmnSCPxj. BCH is a warmup question for several reasons, I
believe they don't even support segwit (!) so lightning would be unsafe due
to their txid mutability bug. I agree altcoin support should be lower
priority, whenever it is obvious which is the altcoin (as indeed, is
abundantly clear wrt BTC vs BCH). But it might one day become unclear.

I remain concerned about safety despite BIP 50 scenarios, forks with more
legitimate contention than so far seen, and also system stability in face
of increasingly unsophisticated / gullible user base. As a cryptocurrency
is little more than a trustless consensus mechanism, it seems circular to
assume consensus in its design, especially if there are entities
financially motivated to fracture that consensus. Resilience against forks
would seem core to safety. If I think of a concrete solution, I'll send it
first to this list for discussion - as I believe that is the preferred
process?

Thanks,
Ben

On Tue, Jan 30, 2018 at 1:16 AM, ZmnSCPxj <ZmnSCPxj at protonmail.com> wrote:

> Good morning Ben,
>
> Hi,
>
> One topic I can't seem to find in the BOLTs is how lightning nodes
> maintain consensus during or after a fork of the underlying blockchain(s).
> For example, channel_announcement messages use a chain_hash, defined as
> hash of underlying block chain's genesis block, to identify the currency in
> use. Today, one might ask which hash identifies BTC as opposed to BCH?
>
>
> I believe the rough consensus among most Lightning developers is that BTC
> is "the real BTC" and gets the Satoshi genesis hash, while BCH is an
> altcoin that was forked off BTC and gets as hash the branching-off point.
> You could try to convince people developing and using Lightning software to
> do the reverse, but I think it is unlikely that many people would agree to
> that.
>
>
> A more difficult question arises in how existing channels handle
> intentional forks which arise after funding of a payment channel.
>
> An even more difficult question arises in the handling of unintentional
> forks, as documented for example in BIP 50.
>
> Have these scenarios been analyzed / designed yet, or does that work
> remain?
>
>
> The work remains.  For the most part, the priority is to get
> implementations to a state, where we can safely deploy on Bitcoin Mainnet.
> Then optimize further by adding RBF and multi-channel funding, then
> integrate Burchert-Decker-Wattenhofer channel factories, splicing, and so
> on.  Greater support for altcoins can be done later.
>
> For forked altcoins, short channel IDs contain the block height at which
> the funding transaction confirmed.  This might be used to judge if a
> channel contains forked coins or not.
>
> Regards,
> ZmnSCPxj
>
>
> Thanks!
> Ben
>
>
>
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