Date: Sat, 29 Jun 2019 14:21:03 -0400
From: "David A. Harding" <dave@dtrt.org>
To: Tamas Blummer <tamas.blummer@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <20190629182103.sbbm4z54svxircbl@ganymede>
References: <0DBC0DEA-C999-4AEE-B2E1-D5337ECD9405@gmail.com>
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Subject: Re: [bitcoin-dev] Generalized covenants with taproot enable
 riskless or risky lending,
 prevent credit inflation through fractional reserve
Precedence: list

On Fri, Jun 28, 2019 at 10:27:16AM +0200, Tamas Blummer via bitcoin-dev wrote:
> The value of these outputs to Charlie is the proof that he has
> exclusive control of the coins until maturity.
>
> Alice can not issue promissory notes in excess of own capital or
> capital that she was able to borrow. No coin inflation or fractional
> reserve here, which also reduces the credit risk Charlie takes.

I believe these goals are obtainable today without any consensus
changes.  Bob can provably timelock bitcoins using CLTV or CSV in a
script that commits to the outpoint (txid, vout) of an output that will
be used as a colored coin to track the debt instrument.  The colored
coin, which has no appreciable onchain value itself, can then be
trustlessly traded, e.g. from Alice to Charlie to Dan as you describe.  

Anyone with a copy of the script Bob paid, the confirmed transaction he
included it in, and the confirmed transaction history of the colored
coin can trustlessly verify the ownership record---including that no
inflation or fractional reserve occurred.

I believe the RGB working group has set for itself the goal[1] of making
trustless colored coin protocols more efficient when performed on top of
Bitcoin.  I'd also suggest reading about Peter Todd's concept of
single-use seals[2].  You may want to investigate these ideas and see
whether they can be integrated with your own.

[1] https://github.com/rgb-org/spec/blob/master/00-introduction.md
[2] https://petertodd.org/2016/commitments-and-single-use-seals#bitcoin-transaction-outputs-as-single-use-seals

-Dave