From rusty at rustcorp.com.au  Mon Jul 27 02:28:12 2015
From: rusty at rustcorp.com.au (Rusty Russell)
Date: Mon, 27 Jul 2015 11:58:12 +0930
Subject: [Lightning-dev] Single-funder anchor model?
Message-ID: <87egjupc5f.fsf@rustcorp.com.au>

Hi all,

        This mentioned on the weekend via #lightning-dev (sorry, still
not archived) from go1111111:

        https://bitcointalk.org/index.php?topic=1134319.new#new

Basically it points out that a single-funder anchor can be done without
requiring new sighash ops nor losing outsourcability.

The other end can transfer funds (if it wants to balance the channel) in
two obvious ways.  The first is to use the lightning network as normal
(via some other channel it already has).  The second (from AJ) is to use
the atomic cross-blockchain idea[1] to atomically transfer funds in from
native bitcoin.

Pros:
        1. Fairly simple.
        2. Outsourcability.

Cons:
        1. Asymmetric creation risk
        2. Wants cross-chain atomic txs sooner
        3. Takes twice the time to get a full two-way channel

The asymmetric risk is as much a feature as a problem: with the
dual-anchor proposal, either side could abort with no penalty and make
the other side wait for the escape timeout anyway.

We've handwaved over the incentives for channel creation so far; they're
tied with routing, and not immediately clear to me.  But it doesn't seem
unreasonable that if you connect to a hub, you front the funds.

Thoughts?
Rusty.

[1] https://bitcointalk.org/index.php?topic=1036208.0 and discussed earlier
    on the list[2]
[2] Still agitating to have those early archives merged into the lf ones...