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From: Eric Voskuil <eric@voskuil.org>
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Date: Fri, 5 Jul 2019 16:44:45 -0700
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To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Generalized covenants with taproot enable
	riskless or risky lending,
	prevent credit inflation through fractional reserve
Precedence: list



> On Jul 5, 2019, at 16:16, ZmnSCPxj <ZmnSCPxj@protonmail.com> wrote:
>=20
> Good morning Eric,
>=20
>=20
> Sent with ProtonMail Secure Email.
>=20
> =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original M=
essage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
> On Saturday, July 6, 2019 3:27 AM, Eric Voskuil <eric@voskuil.org> wrote:
>=20
>>> On Jul 4, 2019, at 21:05, ZmnSCPxj ZmnSCPxj@protonmail.com wrote:
>>> Good morning Eric,
>>>=20
>>>> As with Bitcoin mining, it is the consumed cost that matters in this sc=
enario, (i.e., not the hash rate, or in this case the encumbered coin face v=
alue). Why would the advertiser not simply be required to burn .1 coin for t=
he same privilege, just as miners burn energy? Why would it not make more se=
nse to spend that coin in support of the secondary network (e.g. paying for c=
onfirmation security), just as with the burning of energy in Bitcoin mining?=

>>=20
>> Good morning ZmnSCPxj,
>>=20
>>> Using the unspentness-time of a UTXO allows for someone advertising a se=
rvice or producer to "close up shop" by simply spending the advertising UTXO=
.
>>> For instance, if the advertisement is for sale of a limited stock of goo=
ds, once the stock has been sold, the merchant (assuming the merchant used o=
wn funds) can simply recover the locked funds, with the potential to reinves=
t them elsewhere.
>>> This allows some time-based hedging for the merchant (they may be willin=
g to wait indefinitely for the stock to be sold, but once the stock is sold,=
 they can immediately reap the rewards of not having their funds locked anym=
ore).
>>=20
>> This is a materially different concept than proposed by Tamas.
>>=20
>> =E2=80=9C...he gives up his control of the coins until maturity, he can n=
ot use them elsewhere until then.=E2=80=9D
>=20
> Possibly.
> In a way, this is giving up control of the coin, until he no longer needs t=
he advertisement, i.e. dynamically select the maturity age needed.
>=20
>>> Similarly, an entity renting out a UTXO for an advertisement might allow=
 for early reclamation of the UTXO in exchange for partial refund of fee; as=
 the value in the UTXO is now freed to be spent elsewhere, the lessor can le=
ase it to another advertiser.
>>=20
>> You appear to be proposing a design whereby either the owner or the rente=
r (not entirely clear to me which) can spend the =E2=80=9Clocked up=E2=80=9D=
 coin at any time (no maturity constraint), by dropping the covenant.
>>=20
>> If the renter can do this he can simply steal the coin from the owner.
>>=20
>> If the owner can do this there is no value to the renter (or as a proof o=
f cost), as the owner retains full control of the coin.
>>=20
>=20
> Obviously this will require a 2-of-2 multisig, with an timelocked transact=
ion that lets the owner recover at a futuredate, so that it is the agreement=
 of *both* that is needed to perform any actions before the timelock.
> I already described this in the link I provided.
>=20
>=20
>> If you mean that the age of the encumbrance is the proof of cost, this re=
quires no covenant. I don=E2=80=99t believe this is what you intended, just c=
overing all bases.
>=20
> Not age of encumbrance, quite.
> Instead, it is the simple fact that the UTXO is a UTXO (and not yet spent)=
, that validates the advertisement.

Not any UTXO then, one that with sufficient time-locked coin.

> No, it does not *require* a covenant.
> However, covenants do make it easier to use, in the sense that the renter c=
an repurpose the UTXO (e.g. change details of advertisement) without having t=
o contact the owner.

So how does one get the owner to sign off on the multisig release? Presumabl=
y the renter cares because he wants to recover the remaining value of rental=
. So he not only needs to contact the owner, he also needs to negotiate with=
 the owner for a pro-rated refund. In other words, he must sell the remainin=
g portion of the rental return - essentially how I described it previously. H=
e might as well just sell the marketable ad space that he controls through t=
he remainder of the term (the same value).

Certainly the owner could given him a partially-signed transaction, returnin=
g the coin, allowing the renter to exit at any time, but the renter has no r=
eason to sign it without a refund, which must be pro-rated in some way, impl=
ying later contact/negotiation with the owner.

But it=E2=80=99s worth noting that early recovery of the UTXO entirely elimi=
nates the value of the time lock cost to the ad market. The most obvious exa=
mple is one encumbering the coin to himself, then releasing it with his own t=
wo signatures whenever he wants. In other words, there is no encumbrance at a=
ll, just a bunch of pointless obscurantion.

>>> Burnt funds cannot be "un-burnt" to easily signal the end of a term for a=
n advertisement.
>>=20
>> And as I have shown above, nor can a =E2=80=9Clocked-up=E2=80=9D coin be u=
nlocked to do the same.
>=20
> You have shown no such thing, merely shown that you have not understood th=
e proposal.

I think I understand the implications of it clearly. Feel free to point out w=
hat I=E2=80=99m missing. But I don=E2=80=99t spend any time in implementatio=
n details until I can justify those implications.

A multisig doesn=E2=80=99t fix the central economic issue, which it is not c=
lear that you understand. If so it hasn=E2=80=99t been demonstrated. A cost c=
reated by making coin unusable for a term is not an actual cost if that lock=
 can be released at any time before maturity of that term. Furthermore, cost=
 is most easily demonstrated by simply spending.=20

By analogy, proof of work is simply proof of a spend (incurred cost). Imagin=
e if one demonstrated that cost by =E2=80=9Clocking up=E2=80=9D coin for a y=
ear, and then after the block was accepted, he unlocked that coin after just=
 one day.

Best,
Eric

> Regards,
> ZmnSCPxj