Subject: Re: [bitcoin-dev] Committed bloom filters for improved wallet performance and SPV security

From: Chris Priest <[email-masked]>
Date: Fri, 6 Jan 2017 12:15:46 -0800

Its a method for determining the probability that a valid tx will be
mined in a block before that tx actually gets mined, which is useful
when accepting payments in situations when you can't wait for the full
confirmation. No one is saying all tx validation should be performed
by querying miners mempools, that's ridiculous. Obviously once the tx
gets it's first confirmation, you go back to determining validity the
way you always have. There is no "security catastrophe".

Even if you're running a full node, you can't know for certain that
any given tx will make it into a future block. You can't be certain
the future miner who finally does mine that tx will mine your TXID or
another TXID that spends the same inputs to another address (a double
spend). The only way to actually know for certain is to query every
single large hashpower mempool.

On 1/4/17, Eric Voskuil <[email-masked]> wrote:
> On 01/04/2017 11:06 PM, Chris Priest via bitcoin-dev wrote:
>> On 1/3/17, Jonas Schnelli via bitcoin-dev
>> <[email-masked]> wrote:
>>>
>>> There are plenty, more sane options. If you can't run your own full-node
>>> as a merchant (trivial), maybe co-use a wallet-service with centralized
>>> verification (maybe use two of them), I guess Copay would be one of
>>> those wallets (as an example). Use them in watch-only mode.
>>
>> The best way is to connect to the mempool of each miner and check to
>> see if they have your txid in their mempool.
>>
>> https://www.antpool.com/api/is_in_mempool?txid=334847bb...
>> https://www.f2pool.com/api/is_in_mempool?txid=334847bb...
>> https://bw.com/api/is_in_mempool?txid=334847bb...
>> https://bitfury.com/api/is_in_mempool?txid=334847bb...
>> https://btcc.com/api/is_in_mempool?txid=334847bb...
>>
>> If each of these services return "True", and you know those services
>> so not engage in RBF, then you can assume with great confidence that
>> your transaction will be in the next block, or in a block very soon.
>> If any one of those services return "False", then you must assume that
>> it is possible that there is a double spend floating around, and that
>> you should wait to see if that tx gets confirmed. The problem is that
>> not every pool runs such a service to check the contents of their
>> mempool...
>>
>> This is an example of mining centralization increasing the security of
>> zero confirm.
>
> A world connected up to a few web services to determine payment validity
> is an example of a bitcoin security catastrophe.
>
> e
>
>