Date: Thu, 24 Jan 2019 10:03:25 +0000
To: Dustin Dettmer <dustinpaystaxes@gmail.com>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Proof-of-Stake Bitcoin Sidechains
Precedence: list

Good morning Dustin,

> Wouldn=E2=80=99t a revealed private key for time locked funds create a ra=
ce to spend? I imagine miners who are paying attention would have the advan=
tage but it would still just be a race.

If Bitcoin had implemented RBF "properly" (i.e. not have the silly "opt-out=
" rule) then such races are won by bidding up the fees.  A random person wh=
o is not the original staker would be willing to pay miners a fee up to the=
 entire staked amount minus dustlimit satoshis; obviously a staker would be=
 far less willing to pay up such a fee, so the random person slashing the f=
unds would have a major advantage in that race.
Thus the race will be won by whoever mines the highest-fee transaction.
It still becomes very unlikely that the staker will win unless the staker a=
lready has a significant mining hashpower (and if the staker has significan=
t hashpower, then the Bitoin layer itself is at peril anyway, never mind si=
dechains built on top of it).

Regards,
ZmnSCPxj

>
> On Tue, Jan 22, 2019 at 6:14 AM ZmnSCPxj via bitcoin-dev <bitcoin-dev@lis=
ts.linuxfoundation.org> wrote:
>
> > Good Morning Matt,
> >
> > > ### ZmnSCPxj,
> > >
> > > I'm intrigued by this mechanism of using fixed R values to prevent mu=
ltiple signatures, but how do we derive the R values in a way where they ar=
e
> > unique for each blockheight but still can be used to create signatures =
or verify?
> >
> > One possibility is to derive `R` using standard hierarchical derivation=
.
> > Then require that the staking pubkey be revealed to the sidechain netwo=
rk as actually being `staking_pubkey =3D P + hash(P || parent_R) * G` (poss=
ibly with some trivial protection against Taproot).
> > To sign for a blockheight `h`, you must use your public key `P` and the=
 specific `R` we get from hierarchical derivation from `parent_R` and the b=
lockheight as index.
> >
> > Regards,
> > ZmnSCPxj
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev