From: Mike Hearn <mike@plan99•net>
To: "Michael Grønager" <gronager@mac•com>
Cc: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>
Subject: Re: [Bitcoin-development] [RFC] [BIP proposal] Dealing with malleability
Date: Thu, 20 Feb 2014 14:08:59 +0000 [thread overview]
Message-ID: <CANEZrP26U3BjEi66xjD9SRxrAupGmYC6mKiYYw27BH3q1b1hLQ@mail.gmail.com> (raw)
In-Reply-To: <81A62AB7-9EC6-439E-96CF-F064F0151BB9@mac.com>
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We've done forking changes before much faster than a year and that was with
less experience. If we want, we can get this done within months.
On 20 Feb 2014 16:30, "Michael Gronager" <gronager@mac•com> wrote:
> As I see the BIP it is basically stressing that ver 1 transactions are
> malleable.
>
> It then addresses the need for unmalleable transactions for e.g. spending
> unconfirmed outputs in a deterministic way (i.e. no 3rd party can sabotage)
> - this transaction type is defined as ver 3.
>
> A lot of clients today spend unconfirmed outputs (even bitcoin-qt) and as
> such make an implicit assumption that this is kind of safe, which it is not
> - it can be intervened and sabotaged through tx malleability.
>
> What I suggested was to ensure that a subclass of version 1 transactions
> become unmalleable - namely those with sighash=all. Note that only the
> sender can modify the sighash as it is part of the hash signed. So instead
> of defining a version 3, we could constrain version 1 txes with sighash=all
> to have a unmalleable hash. If you e.g. would like to still have a
> sighash=all type of transaction with malleable features you can simply use
> that sighash=all today is checked for using sighash&0x1f=sighash_all, so
> just OR'ing with 0x20 or 0x40 will get you the 'old' feature.
>
> I do however buy the argument of Peter and Gregory that there might exist
> unpublished transactions out there that does not even conform to the DER
> rules etc, and as such we cannot forbid them from being mined, nor can we
> timestamp them and include 'only the old ones'. Hence we cannot change the
> consensus rule for version 1 transactions - and only changing the relay
> rules will not provide a certain guarantee.
>
> So, I think the two line argument for the BIP is as follows:
> 1. We cannot change the consensus rules for version 1 transactions as that
> might invalidate unpublished non-standard transactions (= voiding peoples
> money, which is a line we don't want to cross)
> 2. The prime usecase for unmalleable transactions is being able to spend
> unconfirmed outputs - this is done today by almost all clients, but it is
> really broken. Hence a need for a fix asap.
>
> I am all in favor for the BIP, but I expect the realistic timeline for
> enforced version 3 transactions is roughly one year, which is better than
> two, but it would have been nice to get it faster...
>
> /M
>
>
> On Feb 19, 2014, at 10:11 PM, Pieter Wuille <pieter.wuille@gmail•com>
> wrote:
>
> > On Wed, Feb 19, 2014 at 9:28 PM, Michael Gronager <gronager@mac•com>
> wrote:
> >> I think that we could guarantee fewer incidents by making version 1
> transactions unmalleable and then optionally introduce a version 3 that
> supported the malleability feature. That way most existing problematic
> implementations would be fixed and no doors were closed for people
> experimenting with other stuff - tx v 3 would probably then be called
> experimental transactions.
> >
> > Just to be clear: this change is not directly intended to avoid
> > "incidents". It will take way too long to deploy this. Software should
> > deal with malleability. This is a longer-term solution intended to
> > provide non-malleability guarantees for clients that a) are upgraded
> > to use them b) willing to restrict their functionality. As there are
> > several intended use cases for malleable transactions (the sighash
> > flags pretty directly are a way to signify what malleabilities are
> > *wanted*), this is not about outlawing malleability.
> >
> > While we could right now make all these rules non-standard, and
> > schedule a soft fork in a year or so to make them illegal, it would
> > mean removing potential functionality that can only be re-enabled
> > through a hard fork. This is significantly harder, so we should think
> > about it very well in advance.
> >
> > About new transaction and block versions: this allows implementing and
> > automatically scheduling a softfork without waiting for wallets to
> > upgrade. The non-DER signature change was discussed for over two
> > years, and implemented almost a year ago, and we still notice wallets
> > that don't support it. We can't expect every wallet to be instantly
> > modified (what about hardware wallets like the Trezor, for example?
> > they may not just be able to be upgraded). Nor is it necessary: if
> > your software only spends confirmed change, and tracks all debits
> > correctly, there is no need.
> >
> > --
> > Pieter
>
>
>
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next prev parent reply other threads:[~2014-02-20 14:09 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-09 23:33 Pieter Wuille
2014-02-10 3:00 ` Peter Todd
2014-02-12 15:12 ` Rune Kjær Svendsen
2014-02-12 16:22 ` Alan Reiner
2014-02-12 16:38 ` Allen Piscitello
2014-02-12 16:44 ` Alan Reiner
2014-02-12 20:27 ` Mark Friedenbach
2014-02-12 22:52 ` Luke-Jr
2014-02-13 0:39 ` Alex Morcos
2014-02-13 0:47 ` Gregory Maxwell
2014-02-19 14:11 ` Michael Gronager
2014-02-19 14:38 ` Pieter Wuille
2014-02-19 20:28 ` Michael Gronager
2014-02-19 20:39 ` Gregory Maxwell
2014-02-19 20:49 ` Peter Todd
2014-02-19 21:05 ` Gregory Maxwell
2014-02-19 21:11 ` Pieter Wuille
2014-02-20 0:22 ` Natanael
2014-02-20 1:29 ` Allen Piscitello
2014-02-20 7:50 ` Natanael
2014-02-20 10:59 ` Michael Gronager
2014-02-20 14:08 ` Mike Hearn [this message]
2014-02-20 14:15 ` Gregory Maxwell
2014-02-20 14:29 ` Gavin Andresen
2014-02-20 14:36 ` Gregory Maxwell
2014-02-20 14:58 ` Gavin Andresen
2014-02-20 15:11 ` Pieter Wuille
2014-02-20 15:24 ` Gregory Maxwell
2014-02-21 6:07 ` Mike Hearn
2014-02-21 6:30 ` Gregory Maxwell
2014-02-19 19:15 ` Jeremy Spilman
2014-02-12 17:13 ` Jeff Garzik
2014-02-12 17:21 ` Pieter Wuille
2014-02-12 18:03 ` Gregory Maxwell
[not found] ` <CALf2ePyQeOxL3d+QoaWSYy_cCKaF9qq1StBwXFms9NyedUg3eg@mail.gmail.com>
2014-02-12 18:21 ` Alan Reiner
2014-02-10 4:39 ` Luke-Jr
2014-02-12 16:56 ` Pavol Rusnak
2014-02-12 17:22 ` Pieter Wuille
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