From: Peter Todd <pete@petertodd•org>
To: Sergio Demian Lerner <sergio.d.lerner@gmail•com>
Cc: bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Trusted merkle tree depth for safe tx inclusion proofs without a soft fork
Date: Sat, 9 Jun 2018 08:45:16 -0400 [thread overview]
Message-ID: <20180609124516.6ms6t7r5t7ikved6@petertodd.org> (raw)
In-Reply-To: <CAKzdR-rz2-D5pbcoSw0CK9tR-UY46ybYaZDmUMYTjBgvkL6ugg@mail.gmail.com>
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On Sat, Jun 09, 2018 at 02:21:17PM +0200, Sergio Demian Lerner wrote:
> Also it must be noted that an attacker having only 1.3M USD that can
> brute-force 72 bits (4 days of hashing on capable ASICs) can perform the
> same attack, so the attack is entirely feasible and no person should accept
> more than 1M USD using a SPV wallet.
That doesn't make any sense. Against a SPV wallet you don't need that attack;
with that kind of budget you can fool it by just creating a fake block at far
less cost, along with a sybil attack. Sybils aren't difficult to pull off when
you have the budget to be greating fake blocks.
> Also the attack can be repeated: once you create the "extension point"
> block, you can attack more and more parties without any additional
> computation.
That's technically incorrect: txouts can only be spent once, so you'll need to
do 2^40 work each time you want to repeat the attack to grind the matching part
of the prevout again.
--
https://petertodd.org 'peter'[:-1]@petertodd.org
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next prev parent reply other threads:[~2018-06-09 12:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 17:13 Peter Todd
2018-06-07 21:15 ` Bram Cohen
2018-06-07 22:20 ` Peter Todd
2018-06-09 3:29 ` Bram Cohen
2018-06-09 11:03 ` Sergio Demian Lerner
2018-06-09 12:21 ` Sergio Demian Lerner
2018-06-09 12:24 ` Sergio Demian Lerner
2018-06-09 12:45 ` Peter Todd [this message]
2018-06-09 12:51 ` Sergio Demian Lerner
2018-06-09 13:02 ` Peter Todd
2018-06-09 12:50 ` Peter Todd
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