[Bitcoin-development] SPV clients and relaying double spends

[Aaron Voisine]

Something like that would be a great help for SPV clients that can't
detect double spends on their own. (still limited of course to sybil
attack concerns)

Aaron Voisine
breadwallet.com


On Thu, Sep 25, 2014 at 7:07 PM, Matt Whitlock <bip at mattwhitlock.name> wrote:
> 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
>