From: Rusty Russell <rusty@rustcorp•com.au>
To: Russell O'Connor <roconnor@blockstream•io>,
Pieter Wuille <pieter.wuille@gmail•com>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>,
Russell O'Connor <roconnor@blockstream•com>,
Kalle Alm <kalle.alm@gmail•com>
Subject: Re: [bitcoin-dev] BIP 117 Feedback
Date: Tue, 16 Jan 2018 11:36:14 +1030 [thread overview]
Message-ID: <87zi5ehat5.fsf@rustcorp.com.au> (raw)
In-Reply-To: <CAMZUoKn4noCEQR6eqf9hiZSMdk-3b8UHR1NrEFrKNoLSMzVjGQ@mail.gmail.com>
"Russell O'Connor" <roconnor@blockstream•io> writes:
> However, if I understand correctly, the situation for BIP 117 is entirely
> different. As far as I understand there is currently no restrictions about
> terminating a v0 witness program with a non-empty alt-stack, and there are
> no restrictions on leaving non-canonical boolean values on the main stack.
BIP-141: "The script must not fail, and result in exactly a single TRUE
on the stack." And it has long been non-standard for P2SH scripts to
not do the same (don't know exactly when).
> There could already be commitments to V0 witness programs that, when
> executed in some reasonable context, leave a non-empty alt-stack and/or
> leave a non-canonical true value on the main stack. Unlike the P2SH or
> Segwit soft-forks, these existing commitments could be real outputs that
> currently confer non-trivial ownership over their associated funds. If BIP
> 117 were activated, these commitments would be subject to a new set of
> rules that didn't exist when the commitments were made. In particular,
> these funds could be rendered unspendable. Because segwit commitments are
> hashes of segwit programs, there is no way to even analyze the blockchain
> to determine if these commitments currently exist (and even if we could it
> probably woudln't be adequate protection).
The rule AFAICT is "standard transactions must still work". This was
violated with low-S, but the transformation was arguably trivial.
OTOH, use of altstack is completely standard, though in practice it's
unused and so only a theoretical concern.
My concern remains unanswered: I want hard numbers on the worst-case
time taken by sigops with the limit removed. It's about 120 usec per
sigop (from [1]), so how bad could it be? I think Russell had an
estimate like 1 in 3 ops, so 160 seconds to validate a block?
Thanks,
Rusty.
[1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-December/015346.html
next prev parent reply other threads:[~2018-01-16 2:27 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-09 11:22 Rusty Russell
2018-01-09 12:40 ` Mark Friedenbach
2018-01-09 14:21 ` Pieter Wuille
2018-01-09 22:57 ` Mark Friedenbach
2018-01-12 10:48 ` Russell O'Connor
2018-01-16 1:06 ` Rusty Russell [this message]
2018-01-16 3:27 ` Gregory Maxwell
2018-01-16 4:15 ` Luke Dashjr
2018-01-16 8:39 ` Russell O'Connor
2018-03-05 15:28 ` Johnson Lau
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