From: Sergio Demian Lerner <sergio.d.lerner@gmail•com>
To: Peter Todd <pete@petertodd•org>
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 14:51:55 +0200 [thread overview]
Message-ID: <CAKzdR-omk7wCk5c_9T28O2Hc-Uzui5S4B_BuDLFt27RWSFzdJw@mail.gmail.com> (raw)
In-Reply-To: <20180609124516.6ms6t7r5t7ikved6@petertodd.org>
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Yo can fool a SPV wallet even if it requires a thousands confirmations
using this attack, and you don't need a Sybil attack, so yes, it impacts
SPV wallets also. The protections a SPV node should have to prevent this
attack are different, so it must be considered separately.
It should be said that a SPV node can avoid accepting payments if any
Merkle node is at the same time a valid transaction, and that basically
almost eliminates the problem.
SPV Wallet would reject valid payments with a astonishingly low probability.
On Sat, Jun 9, 2018 at 2:45 PM Peter Todd <pete@petertodd•org> wrote:
> 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 12:52 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
2018-06-09 12:51 ` Sergio Demian Lerner [this message]
2018-06-09 13:02 ` Peter Todd
2018-06-09 12:50 ` Peter Todd
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