From: Sjors Provoost <sjors@sprovoost•nl>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Address expiration times should be added to BIP-173
Date: Fri, 29 Sep 2017 10:18:06 +0300 [thread overview]
Message-ID: <3CCFB7B0-10FC-4860-86C0-29472B76B129@sprovoost.nl> (raw)
In-Reply-To: <20170929021846.GB12303@savin.petertodd.org>
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Op 29 sep. 2017, om 05:18 heeft Peter Todd <pete@petertodd•org> het volgende geschreven:
>
> On Thu, Sep 28, 2017 at 03:43:05PM +0300, Sjors Provoost via bitcoin-dev wrote:
>> Peter Todd wrote:
>> Perhaps outside the scope of BIP173, but what about baking it into the protocol? That way a transaction that's sent too late, simply won't get confirmed. This removes the need for refund logic or asking a customer to pay just a few extra cents. You could also disallow a second payment.
>>
>> Two downsides I can think of:
>> * privacy, as differences in expiration policy would be visible on chain
>> * miners might be able to game it in their interaction with brokers
>
> This has been discussed many times before; there are *severe* downsides to
> making it possible for transactions to become invalid after the fact.
I've heard of that general principe, but I'm having trouble finding a good resource that describes it more precisely.
Is it a peer to peer or mempool issue? E.g a transaction might be accepted into the mempool and relayed at one point in time and suddenly become invalid before they're committed to a block? Or that a node receives a transaction, thinks it's invalid because the address already expired, but then receives an older block later which contains that transaction?
Once in a block, I don't see how it would become invalid later. But as a miner tries to find a block and updates the timestamp, they would have toss the transaction out at some point.
Another objection I can think of, is that the soft fork introducing this change would have to use a transaction type that's non-standard at the moment. This would make it difficult for a non-upgraded node to broadcast such a transaction. The recipient would have to know if the sender has upgraded before communicating an address, which sounds impractical at best.
>>> Being just an expiration time, seconds-level resolution is unnecessary, and
>>> may give the wrong impression. I'd suggest either:
>>>
>>> 1) Hour resolution - 2^24 hours = 1914 years
>>> 2) Month resolution - 2^16 months = 5458 years
>>
>> So that's 4.8 characters for hours, or 3.2 for years, plus checksum space? The shorter the better. Perhaps one or two bits can be used to specify an exponent; a large range seems more useful than high precision. For instance a merchant doesn't care if the customer pays within 10:00:00 minutes or 10:00:01 minutes and you wouldn't care if your address is valid 50 years or 50 years and 3 minutes. This point may be mute if minute level resolution is not practical.
>
> Note that "large range" is a requirement driven by the fact that expiry times
> will inevitably be specified absolutely, not relatively: when the range runs
> out you need to upgrade the standard. Better to use another character and use a
> range that won't run out any time soon.
>
> This wouldn't create a need for more checksum space.
You're right, relative time makes no sense. So it would take 5 characters to get roughly two minute resolution that lasts for 100 years.
Sjors
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next prev parent reply other threads:[~2017-09-29 7:18 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-27 16:06 Peter Todd
2017-09-27 18:15 ` CryptAxe
2017-09-27 19:03 ` Mark Friedenbach
2017-09-27 21:20 ` Peter Todd
2017-09-27 19:35 ` Chris Priest
2017-09-27 20:11 ` CryptAxe
2017-09-27 20:23 ` Nick Pudar
2017-09-27 20:19 ` CryptAxe
2017-09-27 21:09 ` Mark Friedenbach
2017-09-27 21:15 ` Peter Todd
2017-09-28 0:22 ` Gregory Maxwell
2017-09-27 21:33 ` Peter Todd
2017-09-28 0:58 ` Gregory Maxwell
2017-09-29 1:50 ` Peter Todd
2017-09-29 2:06 ` Gregory Maxwell
2017-09-28 10:09 ` Andreas Schildbach
2017-09-28 12:43 ` Sjors Provoost
2017-09-28 14:13 ` Andreas Schildbach
2017-09-28 14:41 ` Sjors Provoost
2017-09-28 15:06 ` Andreas Schildbach
2017-09-28 15:45 ` Sjors Provoost
2017-09-28 16:59 ` Luke Dashjr
2017-09-29 2:18 ` Peter Todd
2017-09-29 7:18 ` Sjors Provoost [this message]
2017-09-29 2:55 ` [bitcoin-dev] Why the BIP-72 Payment Protocol URI Standard is Insecure Against MITM Attacks Peter Todd
2017-09-29 4:21 ` Omar Shibli
2017-09-29 13:14 ` Tomas
2017-09-29 17:40 ` Aymeric Vitte
2017-09-30 15:33 ` Andreas Schildbach
2017-09-29 1:45 ` [bitcoin-dev] Address expiration times should be added to BIP-173 Peter Todd
2017-09-29 8:44 ` Andreas Schildbach
2017-09-29 9:55 ` Peter Todd
2017-09-29 12:45 ` Andreas Schildbach
2017-09-29 13:52 ` Peter Todd
2017-09-29 17:25 ` Gregory Maxwell
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