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Date: Sat, 9 May 2015 14:45:18 -0400
From: Peter Todd <pete@petertodd.org>
To: Jim Phillips <jim@ergophobia.org>
Message-ID: <20150509184518.GA19703@muck>
References: <CANe1mWzBy8-C+CWfwaOLxJ2wokjy8ytQUh2TkRY_Ummn1BpPzw@mail.gmail.com>
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Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] A suggestion for reducing the size of the
 UTXO database
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On Sat, May 09, 2015 at 12:09:32PM -0500, Jim Phillips wrote:
> The vast majority of users are running one of a handful of different wall=
et
> apps: Core, Electrum; Armory; Mycelium; Breadwallet; Coinbase; Circle;
> Blockchain.info; and maybe a few others. The developers of all these
> wallets have a vested interest in the continued usefulness of Bitcoin, and
> so should not be opposed to changing their UTXO selection algorithms to o=
ne
> that reduces the UTXO database instead of growing it.

You can't assume that UTXO growth will be driven by walles at all; the
UTXO set's global consensus functionality is incredibly useful and will
certainly be used by all manner of applications, many having nothing to
do with Bitcoin.

As one of many examples, here's a proposal - with working code - to use
the UTXO set to get consensus over TLC certificate revocations. The
author, Christopher Allen, was one of the co-authors of the SSL
standard:

https://github.com/ChristopherA/revocable-self-signed-tls-certificates-hack

There's nothing we can do to stop these kinds of usages other than
forcing users to identify themselves to get permission to use the
Bitcoin blockchain. Using the Bitcoin blockchain gives their users
significantly better security in many cases than any alternatives, so
there's strong incentives to do so. Finally, the cost many of these
alternative uses are willing to pay pre UTXO/transaction is
significantly higher than the fees many existing Bitcoin users can pay
to make transactions.

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