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From: Peter Todd <pete@petertodd.org>
To: "Russell O'Connor" <roconnor@blockstream.io>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Fast Merkle Trees
Date: Thu, 7 Sep 2017 01:55:57 -0400	[thread overview]
Message-ID: <20170907055557.GA12638@fedora-23-dvm> (raw)
In-Reply-To: <CAMZUoKmD4v4vn9L=kdyJNk-km3XHpNVkD_tmS+SseMsf6YaVPg@mail.gmail.com>

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On Wed, Sep 06, 2017 at 09:59:54PM -0400, Russell O'Connor via bitcoin-dev wrote:
> The fast hash for internal nodes needs to use an IV that is not the
> standard SHA-256 IV. Instead needs to use some other fixed value, which
> should itself be the SHA-256 hash of some fixed string (e.g. the string
> "BIP ???" or "Fash SHA-256").

Note that in general, designs should *not* create new hash functions by using
custom IVs, but rather use bog-standard SHA256, and make a fixed first block.
That allows unoptimised implementations to just hash a block with the second
initialization value, and optimized implementations to start with the fixed
midstate.

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

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  parent reply	other threads:[~2017-09-07  5:56 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-07  1:59 [bitcoin-dev] Fast Merkle Trees Russell O'Connor
2017-09-07  2:20 ` Mark Friedenbach
2017-09-07 15:43   ` Russell O'Connor
2017-09-07 17:42     ` Mark Friedenbach
2017-09-07 18:55       ` Russell O'Connor
2017-09-07 20:04         ` Mark Friedenbach
2017-09-12 11:44           ` Johnson Lau
2017-09-07  5:55 ` Peter Todd [this message]
2017-09-07 15:51   ` Russell O'Connor

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