Date: Tue, 27 Jun 2017 00:13:08 -0400
From: Peter Todd <pete@petertodd.org>
To: "Russell O'Connor" <roconnor@blockstream.io>
Message-ID: <20170627041308.GA23776@savin.petertodd.org>
References: <CAMZUoK=f3hXHkqJBDfiLGSrgXi_ppgyH6+XWD9W54EYFWLm1+Q@mail.gmail.com>
	<20170528082624.GA14552@fedora-23-dvm>
	<CAMZUoK=8xaVp2Qoc7kvx8FdPbpY0rEpSba8kQVRQGjX4p0haxg@mail.gmail.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] A Method for Computing Merkle Roots of Annotated
 Binary Trees
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On Mon, May 29, 2017 at 10:55:37AM -0400, Russell O'Connor wrote:
> > This doesn't hold true in the case of pruned trees, as for the pruning =
to
> > be
> > useful, you don't know what produced the left merkleRoot, and thus you
> > can't
> > guarantee it is in fact a midstate of a genuine SHA256 hash.
> >
>=20
> Thanks for the review Peter.  This does seem like a serious issue that I
> hadn't considered yet.  As far as I understand, we have no reason to think
> that the SHA-256 compression function will be secure with chosen initial
> values.

Relevant: fixed points can be found for the SHA256 compression function, if=
 the
attacker can control the IV:

https://crypto.stackexchange.com/questions/48580/fixed-point-of-the-sha-256=
-compression-function

--=20
https://petertodd.org 'peter'[:-1]@petertodd.org

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