From lf-lists at mattcorallo.com  Mon Jan 27 14:41:58 2020
From: lf-lists at mattcorallo.com (Matt Corallo)
Date: Mon, 27 Jan 2020 14:41:58 +0000
Subject: [Lightning-dev] Not revealing the channel capacity during
 opening of channel in lightning network
In-Reply-To: <02e301d5d4e6$63744af0$2a5ce0d0$@gmail.com>
References: <CAPvY=RiY3SzTRYTYs1mLGZ765GSY=RbDOsaYtQifgeqHh6ck8A@mail.gmail.com>
 <02e301d5d4e6$63744af0$2a5ce0d0$@gmail.com>
Message-ID: <373fd90c-eec6-2347-6315-d99eef47f66a@mattcorallo.com>

Note that there's no real reason lightning nodes *have* to have
confidence in that - if a node routes your payment to the next hop, how
they do it doesn't really matter. Allowing things like non-lightning
"channels" (eg just a contractual agreement to settle up later between
two mutually-trusting parties) would actually be quite compelling.

The reason lightning nodes *today* require proof-of-funds-locked is
largely for DoS resistance, effectively rate-limiting flooding the
global routing table with garbage, but such rate-limiting could be
accomplished (albeit with a ton more complexity) via other means.

Matt

On 1/27/20 7:50 AM, Ugam Kamat wrote:
> Hey Subhra ? In order to have faith that the channel announced by the
> nodes is actually locked on the Bitcoin mainchain we need to have the
> outpoint (`txid` and `vout`) of the funding transaction. If we do not
> verify that the funding transaction has been confirmed, nodes can cheat
> us that a particular transaction is confirmed when it is not the case.
> As a result we require that nodes announce this information along with
> the public keys and the signatures of the public keys that was used to
> lock the funding transaction.
> 
> ?
> 
> This information is broadcasted in the `channel_announcement` message in
> the `short_channel_id` field which includes the block number,
> transaction number and vout. Since Bitcoin does not allow confidential
> transactions, we can query the blockchain and find out the channel
> capacity even when the amounts are never explicitly mentioned.
> 
> ?
> 
> ?
> 
> Ugam
> 
> ?
> 
> *From:* Lightning-dev <lightning-dev-bounces at lists.linuxfoundation.org>
> *On Behalf Of *Subhra Mazumdar
> *Sent:* Monday, January 27, 2020 12:45 PM
> *To:* lightning-dev at lists.linuxfoundation.org
> *Subject:* [Lightning-dev] Not revealing the channel capacity during
> opening of channel in lightning network
> 
> ?
> 
> Dear All,
> 
> ???????? What can be the potential problem if a channel is opened
> whereby the channel capacity is not revealed publicly but just a range
> proof of the attribute (capacity >0 and capacity < value) is provided ?
> Will it pose a problem during routing of transaction ? What are the pros
> and cons ?
> 
> I think that revealing channel capacity make the channels susceptible to
> channel exhaustion attack or a particular node might be targeted for
> node isolation attack ?
> 
> 
> -- 
> 
> Yours sincerely,
> Subhra Mazumdar.
> 
> 
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