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From: Alistair Mann <al@pectw.net>
To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Date: Sun, 17 Mar 2019 16:11:29 +0000
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Pre BIP: Solving for spam and other abuse with an
	HTLB
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Many thanks for your thoughts, ZmnSCPxj.

> I believe there is indeed an important usecase for HTLB over HTLC, which is
> to improve the anonymity set. An HTLB over HTLC would be indistinguishable
> onchain from other uses of HTLC; assuming that HTLCs have other uses, this
> is a (small?) plus to privacy.
> 
> Note that the redundant <digest> would have to be given by Alice to Bob,
> since using a standardized one will also reveal use of HTLB over HTLC
> instead of hiding it among other HTLC UTXOs.

Both these are good observations and I'll act on them.
 
> Another thing to improve privacy would be to apply the Funding Transaction
> pattern: https://zmnscpxj.github.io/offchain/generalized.html
<snip>

I've not read of the FTP before; I welcome it, and take on board that it 
improves privacy by keeping a script offline. My first thought is that doesn't 
affect the suggested BIP, so my next update here won't include it. I recognise 
it would improve mainnet use of scripts though, so do expect to return to it.

Cheers,
-- 
Alistair Mann