From: Luke Dashjr <luke@dashjr.org>
To: Felix Weis <mail@felixweis.com>
Date: Sun, 1 Oct 2017 17:36:05 +0000
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Version 1 witness programs (first draft)
Precedence: list

BIP 115 provides fork-independent opt-in replay protection, which can be us=
ed=20
in combination with the new signature condition scripts in this proposal.

Perhaps the code can have a flag for new altcoins to easily make it mandato=
ry=20
(and we can use it on testnet?).

Luke


On Sunday 01 October 2017 11:22:30 AM Felix Weis wrote:
> Just a simple suggestion since the signature format is changed. Can this =
be
> designed so that possible future hard forks can simply change 1 constant =
in
> the code and turn on cross chain replay protection?
>=20
> On Sun, Oct 1, 2017 at 1:05 PM Mark Friedenbach via bitcoin-dev <
>=20
> bitcoin-dev@lists.linuxfoundation.org> wrote:
> > Clean stack should be eliminated for other possible future uses, the mo=
st
> > obvious of which is recursive tail-call for general computation
> > capability. I=E2=80=99m not arguing for that at this time, just arguing=
 that we
> > shouldn=E2=80=99t prematurely cut off an easy implementation of such sh=
ould we
> > want to. Clean stack must still exist as policy for future soft-fork
> > safety, but being a consensus requirement was only to avoid witness
> > malleability, which committing to the size of the witness also
> > accomplishes.
> >=20
> > Committing to the number of witness elements is fully sufficient, and
> > using the number of elements avoids problems of not knowing the actual
> > size in bytes at the time of signing, e.g. because the witness contains
> > a merkle proof generated by another party from an unbalanced tree, and
> > unbalanced trees are expected to be common (so that elements can be
> > placed higher in the tree in accordance with their higher expected
> > probability of usage). Other future extensions might also have
> > variable-length proofs.
> >=20
> > > On Sep 30, 2017, at 7:47 PM, Luke Dashjr <luke@dashjr.org> wrote:
> > >=20
> > > Should it perhaps commit to the length of the serialised witness data
> >=20
> > instead
> >=20
> > > or additionally? Now that signatures are no longer variable-length,
> >=20
> > that'd be
> >=20
> > > possible...
> > >=20
> > > As far as tail-call needs are concerned, CLEANSTACK wouldn't have been
> >=20
> > checked
> >=20
> > > until AFTER the tail-call in the first draft. But I suppose eliminati=
ng
> >=20
> > it for
> >=20
> > > other possible future purposes is still useful.
> > >=20
> > > Luke
> >=20
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev