From rusty at rustcorp.com.au  Tue Nov 24 03:55:04 2015
From: rusty at rustcorp.com.au (Rusty Russell)
Date: Tue, 24 Nov 2015 14:25:04 +1030
Subject: [Lightning-dev] How to exchange of Revocation preimage
	atomically ?
In-Reply-To: <CA+1nnrn7zGpxALs-cZED-G_44apn4DXL-_gHYzwQ-joO0CpPGQ@mail.gmail.com>
References: <CA+1nnrn7zGpxALs-cZED-G_44apn4DXL-_gHYzwQ-joO0CpPGQ@mail.gmail.com>
Message-ID: <87poz0jbl3.fsf@rustcorp.com.au>

Nicolas Dorier <nicolas.dorier at gmail.com> writes:
> I am still learrning about Lightning Network, slowly but surely.
> As I was reviewing bip 112 (
> https://github.com/btcdrak/bips/blob/bip112sync/bip-0112.mediawiki) I
> noticed that HLTC seems to have a potential attack.
>
> When both parties want to revoke a commitment, they need to send one to
> another the revocation preimage.
> However, if not done atomically, Alice intentionally not send her
> revocation after receiving Bob's thus preventing Bob to withdraw his funds.
>
> Am I missing something ?

The order is:

1. Exchange new commit tx signatures.
2. Exchange revocation of old commit tx.

If Alice doesn't do #2, Bob still has the new commit tx he can drop on
the blockchain.

Cheers,
Rusty.