From: Matt Whitlock <bip@mattwhitlock.name>
To: Aaron Voisine <voisine@gmail.com>
Date: Thu, 25 Sep 2014 22:07:28 -0400
Message-ID: <1447373.AzvO89eGJS@crushinator>
User-Agent: KMail/4.14.1 (Linux/3.14.14-gentoo; KDE/4.14.1; x86_64; ; )
In-Reply-To: <CACq0ZD4Ki=7Tba_2UhmuH-dPCbOnfXrJRcLPc+fP6Uur4FpG_A@mail.gmail.com>
References: <CACq0ZD4Ki=7Tba_2UhmuH-dPCbOnfXrJRcLPc+fP6Uur4FpG_A@mail.gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] SPV clients and relaying double spends
Precedence: list

What's to stop an attacker from broadcasting millions of spends of the same output(s) and overwhelming nodes with slower connections? Might it be a better strategy not to relay the actual transactions (after the first) but rather only propagate (once) some kind of double-spend alert?


On Thursday, 25 September 2014, at 7:02 pm, Aaron Voisine wrote:
> There was some discussion of having nodes relay double-spends in order
> to alert the network about double spend attempts.
> 
> A lot more users will be using SPV wallets in the future, and one of
> the techniques SPV clients use to judge how likely a transaction is to
> be confirmed is if it propagates across the network. I wonder if and
> when double-spend relaying is introduced, if nodes should also send
> BIP61 reject messages or something along those lines to indicate which
> transactions those nodes believe to be invalid, but are relaying
> anyway.
> 
> This would be subject to sybil attacks, as is monitoring propagation,
> however it does still increase the cost of performing a 0 confirmation
> double spend attack on an SPV client above just relaying double-spends
> without indicating if a node believes the transaction to be valid.
> 
> Aaron Voisine
> breadwallet.com