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📅 Original date posted:2018-03-14 📝 Original message:Thank ...

2023-06-07T18:11:12Z

In reply to nevent1q…x6jn
_________________________

📅 Original date posted:2018-03-14
📝 Original message:Thank you.

I can't really see from your proposal if you had thought of this: A soft
fork can make old nodes accept invalid message signatures as valid. For
example, a "signer" can use a witness version unknown to the verifier to
fool the verifier. Witness version is detectable (just reject unknown
witness versions) but there may be more subtle changes. Segwit was not
"detectable" in that way, for example.

This is the reason why I withdrew BIP120. If you have thought about the
above, I'd be very interested.

/Kalle

Sent from my Sinclair ZX81

Den 14 mars 2018 16:10 skrev "Karl Johan Alm via bitcoin-dev" <
bitcoin-dev at lists.linuxfoundation.org>:

Hello,

I am considering writing a replacement for the message signing tools
that are currently broken for all but the legacy 1xx addresses. The
approach (suggested by Pieter Wuille) is to do a script based
approach. This does not seem to require a lot of effort for
implementing in Bitcoin Core*. Below is my proposal for this system:

A new structure SignatureProof is added, which is a simple scriptSig &
witnessProgram container that can be serialized. This is passed out
from/into the signer/verifier.

RPC commands:

sign <address> <message> [<prehashed>=false]

Generates a signature proof for <message> using the same method that
would be used to spend coins sent to <address>.**

verify <address> <message> <proof> [<prehashed>=false]

Deserializes and executes the proof using a custom signature checker
whose sighash is derived from <message>. Returns true if the check
succeeds, and false otherwise. The scriptPubKey is derived directly
from <address>.**

Feedback welcome.

-Kalle.

(*) Looks like you can simply use VerifyScript with a new signature
checker class. (h/t Nicolas Dorier)
(**) If <prehashed> is true, <message> is the sighash, otherwise
sighash=sha256d(message).
_______________________________________________
bitcoin-dev mailing list
bitcoin-dev at lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
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📅 Original date posted:2017-12-18 📝 Original message:Thanks ...

2023-06-07T18:08:49Z

In reply to nevent1q…9pm5
_________________________

📅 Original date posted:2017-12-18
📝 Original message:Thanks Eric.

It would be a pity if early witnesses got lost due to nodes abandoning them
by running witnessless. But as long as there's at least one accessible
source for them left we're OKish. Let's hope we don't get to that point in
the near future. As long as Bitcoin Core doesn't implement witnessless
mode, there's little risk.

What do people here think about the benefits and risks with running
witnessless?

/Kalle

Sent from my Sinclair ZX81

Den 18 dec. 2017 17:19 skrev "Eric Voskuil" <eric at voskuil.org>:

> You can't know (assume) a block is valid unless you have previously
> validated the block yourself. But in the case where you have, and then
> intend to rely on it in a future sync, there is no need for witness data
> for blocks you are not going to validate. So you can just not request it.
>
> However you will not be able to provide those blocks to nodes that *are*
> validating; the client is pruned and therefore not a peer (cannot
> reciprocate). (An SPV client is similarly not a peer; it is a more deeply
> pruned client than the witnessless client.)
>
> There is no other reason that a node requires witness data. SPV clients
> don't need it as it is neither require it to verify header commitment to
> transactions nor to extract payment addresses from them.
>
> The harm to the network by pruning is that eventually it can become harder
> and even impossible for anyone to validate the chain. But because you are
> fully validating you individually remain secure, so there is no individual
> incentive working against this system harm.
>
> e
>
> On Dec 18, 2017, at 08:35, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>
> 2017-12-18 13:43 GMT+01:00 Eric Voskuil <eric at voskuil.org>:
>
>>
>> > On Dec 18, 2017, at 03:32, Kalle Rosenbaum via bitcoin-dev <
>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>> >
>> > Dear list,
>> >
>> > I find it hard to understand why a full node that does initial block
>> > download also must download witnesses if they are going to skip
>> verification anyway.
>>
>> Why run a full node if you are not going to verify the chain?
>>
>
> I meant to say "I find it hard to understand why a full node that does
> initial block
> download also must download witnesses when it is going to skip
> verification of the witnesses anyway."
>
> I'm referring to the "assumevalid" feature of Bitcoin Core that skips
> signature verification up to block X. Or have I misunderstood assumevalid?
>
> /Kalle
>
>
>>
>> > If my full node skips signature verification for
>> > blocks earlier than X, it seems the reasons for downloading the
>> > witnesses for those blocks are:
>> >
>> > * to be able to send witnesses to other nodes.
>> >
>> > * to verify the witness root hash of the blocks
>> >
>> > I suppose that it's important to verify the witness root hash because
>> > a bad peer may send me invalid witnesses during initial block
>> > download, and if I don't verify that the witness root hash actually
>> > commits to them, I will get banned by peers requesting the blocks from
>> > me because I send them garbage.
>> > So both the reasons above (there may be more that I don't know about)
>> > are actually the same reason: To be able to send witnesses to others
>> > without getting banned.
>> >
>> > What if a node could chose not to download witnesses and thus chose to
>> > send only witnessless blocks to peers. Let's call these nodes
>> > witnessless nodes. Note that witnessless nodes are only witnessless
>> > for blocks up to X. Everything after X is fully verified.
>> >
>> > Witnessless nodes would be able to sync faster because it needs to
>> > download less data to calculate their UTXO set. They would therefore
>> > more quickly be able to provide full service to SPV wallets and its
>> > local wallets as well as serving blocks to other witnessless nodes
>> > with same or higher assumevalid block. For witnessless nodes with
>> > lower assumevalid they can serve at least some blocks. It could also
>> > serve blocks to non-segwit nodes.
>> >
>> > Do witnessless nodes risk dividing the network in two parts, one
>> > witnessless and one with full nodes, with few connections between the
>> > parts?
>> >
>> > So basically, what are the reasons not to implement witnessless
>> > nodes?
>> >
>> > Thank you,
>> > /Kalle
>> > _______________________________________________
>> > bitcoin-dev mailing list
>> > bitcoin-dev at lists.linuxfoundation.org
>> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>
>
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📅 Original date posted:2017-12-18 📝 Original message:Hi ...

2023-06-07T18:08:48Z

In reply to nevent1q…tpn0
_________________________

📅 Original date posted:2017-12-18
📝 Original message:Hi Mark

Yes, it seems like sign-to-contract protocols, which I just now briefly
read about [1][2], may need to use historic witnesses. That raises the
question, what are Bitcoin witnesses for?

To me it seems witnesses should be regarded as temporary. But it seems both
respondents to this thread, Eric and Mark, mean that witnesses are forever.
I regard witnesses as a way to authenticate updates to the UTXO set, and
once buried deep enough in the blockchain, the witness is no longer needed,
because consensus has formed around the UTXO set update.

Suppose a transaction with an invalid witness happens to enter the
blockchain and gets buried 100000 blocks down with the witness still
available. Is the blockchain above it valid? I'd say the blockchain is
valid and that it was a bug that the transaction made it into the
blockchain. We will have to live with such bugs.

Another way to put it: Suppose that all witnesses from 2017 dissappears
from all nodes in 2020. Is the blockchain still valid? I think so. I would
continue using it without looking back.

With that approach, I think sign-to-contract protocols has to find ways to
work in a witnessless environment. For example, users of such protocols can
setup their own archival nodes.

I'd love to hear alternative views on this.

Thanks,
/Kalle

[1]
https://download.wpsoftware.net/bitcoin/wizardry/mw-slides/2017-03-mit-bitcoin-expo/slides.pdf
[2] https://bitcointalk.org/index.php?topic=893898.msg9861102#msg9861102

2017-12-18 18:30 GMT+01:00 Mark Friedenbach via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org>:

> Sign-to-contract enables some interesting protocols, none of which are in
> wide use as far as I’m aware. But if they were (and arguably this is an
> area that should be more developed), then SPV nodes validating these
> protocols will need access to witness data. If a node is performing IBD
> with assumevalid set to true, and is also intending to prune history, then
> there’s no reason to fetch those witnesses as far as I’m aware. But it
> would be a great disservice to the network for nodes intending to serve SPV
> clients to prune this portion of the block history.
>
>
> On Dec 18, 2017, at 8:19 AM, Eric Voskuil via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
>
> You can't know (assume) a block is valid unless you have previously
> validated the block yourself. But in the case where you have, and then
> intend to rely on it in a future sync, there is no need for witness data
> for blocks you are not going to validate. So you can just not request it.
>
> However you will not be able to provide those blocks to nodes that *are*
> validating; the client is pruned and therefore not a peer (cannot
> reciprocate). (An SPV client is similarly not a peer; it is a more deeply
> pruned client than the witnessless client.)
>
> There is no other reason that a node requires witness data. SPV clients
> don't need it as it is neither require it to verify header commitment to
> transactions nor to extract payment addresses from them.
>
> The harm to the network by pruning is that eventually it can become harder
> and even impossible for anyone to validate the chain. But because you are
> fully validating you individually remain secure, so there is no individual
> incentive working against this system harm.
>
> e
>
> On Dec 18, 2017, at 08:35, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>
> 2017-12-18 13:43 GMT+01:00 Eric Voskuil <eric at voskuil.org>:
>
>>
>> > On Dec 18, 2017, at 03:32, Kalle Rosenbaum via bitcoin-dev <
>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>> >
>> > Dear list,
>> >
>> > I find it hard to understand why a full node that does initial block
>> > download also must download witnesses if they are going to skip
>> verification anyway.
>>
>> Why run a full node if you are not going to verify the chain?
>>
>
> I meant to say "I find it hard to understand why a full node that does
> initial block
> download also must download witnesses when it is going to skip
> verification of the witnesses anyway."
>
> I'm referring to the "assumevalid" feature of Bitcoin Core that skips
> signature verification up to block X. Or have I misunderstood assumevalid?
>
> /Kalle
>
>
>>
>> > If my full node skips signature verification for
>> > blocks earlier than X, it seems the reasons for downloading the
>> > witnesses for those blocks are:
>> >
>> > * to be able to send witnesses to other nodes.
>> >
>> > * to verify the witness root hash of the blocks
>> >
>> > I suppose that it's important to verify the witness root hash because
>> > a bad peer may send me invalid witnesses during initial block
>> > download, and if I don't verify that the witness root hash actually
>> > commits to them, I will get banned by peers requesting the blocks from
>> > me because I send them garbage.
>> > So both the reasons above (there may be more that I don't know about)
>> > are actually the same reason: To be able to send witnesses to others
>> > without getting banned.
>> >
>> > What if a node could chose not to download witnesses and thus chose to
>> > send only witnessless blocks to peers. Let's call these nodes
>> > witnessless nodes. Note that witnessless nodes are only witnessless
>> > for blocks up to X. Everything after X is fully verified.
>> >
>> > Witnessless nodes would be able to sync faster because it needs to
>> > download less data to calculate their UTXO set. They would therefore
>> > more quickly be able to provide full service to SPV wallets and its
>> > local wallets as well as serving blocks to other witnessless nodes
>> > with same or higher assumevalid block. For witnessless nodes with
>> > lower assumevalid they can serve at least some blocks. It could also
>> > serve blocks to non-segwit nodes.
>> >
>> > Do witnessless nodes risk dividing the network in two parts, one
>> > witnessless and one with full nodes, with few connections between the
>> > parts?
>> >
>> > So basically, what are the reasons not to implement witnessless
>> > nodes?
>> >
>> > Thank you,
>> > /Kalle
>> > _______________________________________________
>> > bitcoin-dev mailing list
>> > bitcoin-dev at lists.linuxfoundation.org
>> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
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📅 Original date posted:2015-07-27 📝 Original message:Ok, ...

2023-06-07T15:43:38Z

In reply to nevent1q…zw6z
_________________________

📅 Original date posted:2015-07-27
📝 Original message:Ok, Thanks
Den 27 jul 2015 11:08 skrev "Jorge Timón" <jtimon at jtimon.cc>:

>
> On Jul 26, 2015 11:13 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
> > Do you think we need a bigger nonce? In that case, why?
>
> I don't know, it wasn't me that proposed a bigger nonce. I just wanted to
> point out that the policy limit shouldn't be a concern.
>
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📅 Original date posted:2015-07-26 📝 Original ...

2023-06-07T15:43:37Z

In reply to nevent1q…cj3p
_________________________

📅 Original date posted:2015-07-26
📝 Original message:(Resending to the new bitcoin-dev list after sending to the old list)

2015-07-25 21:34 GMT+02:00 Jorge Timón <jtimon at jtimon.cc>:
> Then why do you assume they have a policy limit that not even bitcoin core
> itself maintains (the default limit was moved from 42 to 83 [counting the
> op_return and pushes])?
>
> The policy check is not a consensus rule. Other implementations may have
> another default or not have a limit at all.

Thank you for pointing this out.

That's right. Bitcoin core now support 80 bytes data by default. And
yes, I was wrong in assuming 40 bytes policy in all implementations,
even if 40 bytes was the limit in bitcoin core at the time of writing
the BIP.

If there's a need to increase the size of the nonce, for example to
128 bits instead of the 48 bits as designed in BIP 120, then we can of
course do that, either now or in a subsequent version of PoP.

As noted before though, a longer nonce also means bigger QR codes
generated from the BIP 121 URIs. So I think that 48 bits is a good
tradeoff right now. And as stated in BIP120, a server generating PoP
requests should try to detect brute force attacks, or at least delay
the response (containing the nonce) by some 100 ms or so.

Do you think we need a bigger nonce? In that case, why?

If PoP later becomes an extension of BIP70, then there is no such size
constraint on the nonce, since it will be part of some kind of (e.g.)
PopRequest message and not contained in a QR encoded URI.

/Kalle

📅 Original date posted:2015-07-24 📝 Original message:These ...

2023-06-07T15:43:36Z

In reply to nevent1q…hx7p
_________________________

📅 Original date posted:2015-07-24
📝 Original message:These BIPs have been assigned 120 and 121:

120: Proof of Payment
121: Proof of Payment URI scheme

Regards,
Kalle
Den 24 jul 2015 08:27 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:

> These BIPs have been assigned 120 and 121:
>
> 120: Proof of Payment
> 121: Proof of Payment URI scheme
>
> Regards,
> Kalle
> Den 21 jun 2015 16:39 skrev "Kalle Rosenbaum" <kalle at rosenbaum.se>:
>
>> Hi Greg!
>>
>> After a lot of constructive discussion, feedback and updating, I'm
>> requesting that you please assign these proposals BIP numbers. It's both
>> the "Proof of Payment" proposal and the "Proof of Payment URI scheme"
>> proposal that I'm referring to.
>>
>> The wikimedia source is available here:
>> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP.
>>
>> Is this what you need in order to proceed or is there something else you
>> need from me?
>>
>> Best regards,
>> /Kalle
>>
>> 2015-06-17 11:51 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>>
>>> 2015-06-16 21:48 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>>> > I don't see why existing software could create a 40-byte OP_RETURN but
>>> not
>>> > larger? The limitation comes from a relay policy in full nodes, not a
>>> > limitation is wallet software... and PoPs are not relayed on the
>>> network.
>>>
>>> You are probably right here. The thing is that I don't know how *all*
>>> wallet signing and validating software is written, so I figure it's
>>> better to stick to a "valid" output. Since I don't *need* more data
>>> than 40 bytes, why bother. There's another constraint to this as well:
>>> The other BIP proposal, "Proof of Payment URI scheme", includes a
>>> nonce parameter in the URI. If the nonce is very long, the QR code
>>> will be unnecessarily big. The server should try to detect a brute
>>> force of the 48 bit nonce, or at least delay the pop requests by some
>>> 100 ms or so.
>>>
>>> Do you think this is an actual problem, and why? Is your suggestion to
>>> use a bigger nonce, given the above?
>>>
>>> >
>>> > Regarding sharing, I think you're talking about a different use case.
>>> Say
>>> > you want to pay for 1-week valid entrance to some venue. I thought the
>>> > purpose of the PoP was to be sure that only the person who paid for
>>> it, and
>>> > not anyone else can use it during that week.
>>> >
>>>
>>> That's right. That's one use case. You pay for the 1-week entrance and
>>> then you use your wallet to sign PoPs when you enter the venue.
>>>
>>> > My argument against that is that the original payer can also hand the
>>> > private keys in his wallet to someone else, who would then become able
>>> to
>>> > create PoPs for the service. He does not lose anything by this,
>>> assuming the
>>> > address is not reused.
>>> >
>>>
>>> Yes, that is possible. It's about the same as giving out a
>>> username/password for a service that you have paid for. In the case of
>>> a concert ticket, it's simple. Just allow one entrance per payment.
>>> But in the example you gave, it's a bit more complicated. You could
>>> for example give all guests a bracelet upon first entry or upon first
>>> exit. Or you can put a stamp on people leaving the venue, and demand
>>> that all re-entries show the stamp, possibly along with a new PoP.
>>> Pretty much as is done already. Different use cases will need
>>> different protection. In this example, the value added by PoP is that
>>> the venue does not have to distribute tickets in advance. This in turn
>>> allows for better privacy for the customer, who don't have to give out
>>> personal information such as an email-address.
>>>
>>> > So, using a token does not change anything, except it can be provided
>>> to the
>>> > payer - instead of relying on creating an implicit identity based on
>>> who
>>> > seems to have held particular private keys in the past.
>>> >
>>>
>>> Yes, that's a difference, but it comes at the cost of security. The
>>> stolen token can be used over and over. In the case of PoP it's only
>>> usable once, and it's only created when it's actually needed,
>>> minimizing the window of opportunity for the thief.
>>>
>>> Regards,
>>> Kalle
>>>
>>> > On Jun 16, 2015 9:41 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>> >>
>>> >> 2015-06-16 21:25 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>>> >> > You can't avoid sharing the token, and you can't avoid sharing the
>>> >> > private
>>> >> > keys used for signing either. If they are single use, you don't lose
>>> >> > anything by sharing them.
>>> >>
>>> >> Forwarding the PoP request would be a way to avoid sharing keys, as
>>> >> suggested above.
>>> >>
>>> >> >
>>> >> > Also you are not creating a real transaction. Why does the OP_RETURN
>>> >> > limitation matter?
>>> >>
>>> >> This was discussed in the beginning of this thread: "The idea is to
>>> >> simplify implementation. Existing software can be used as is to sign
>>> >> and validate PoPs"
>>> >>
>>> >> Regards,
>>> >> Kalle
>>> >>
>>> >> >
>>> >> > On Jun 16, 2015 9:22 PM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>>> wrote:
>>> >> >>
>>> >> >> Thank you for your comments Pieter! Please find my answers below.
>>> >> >>
>>> >> >> 2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com
>>> >:
>>> >> >> > On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <
>>> kalle at rosenbaum.se>
>>> >> >> > wrote:
>>> >> >> >>
>>> >> >> >> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <
>>> pieter.wuille at gmail.com>:
>>> >> >> >> I'm not sure if we will be able to support PoP with CoinJoin.
>>> Maybe
>>> >> >> >> someone with more insight into CoinJoin have some input?
>>> >> >> >
>>> >> >> >
>>> >> >> > Not really. The problem is that you assume a transaction
>>> corresponds
>>> >> >> > to
>>> >> >> > a
>>> >> >> > single payment. This is true for simple wallet use cases, but not
>>> >> >> > compatible
>>> >> >> > with CoinJoin, or with systems that for example would want to
>>> combine
>>> >> >> > multiple payments in a single transaction.
>>> >> >> >
>>> >> >>
>>> >> >> Yes, you are right. It's not compatible with CoinJoin and the
>>> likes.
>>> >> >>
>>> >> >> >
>>> >> >> > 48 bits seems low to me, but it does indeed solve the problem.
>>> Why
>>> >> >> > not
>>> >> >> > 128
>>> >> >> > or 256 bits?
>>> >> >>
>>> >> >> The nonce is limited because of the OP_RETURN output being limited
>>> to
>>> >> >> 40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.
>>> >> >>
>>> >> >> >
>>> >> >> >> > Why does anyone care who paid? This is like walking into a
>>> >> >> >> > coffeshop,
>>> >> >> >> > noticing I don't have money with me, let me friend pay for
>>> me, and
>>> >> >> >> > then
>>> >> >> >> > have
>>> >> >> >> > the shop insist that I can't drink it because I'm not the
>>> buyer.
>>> >> >> >>
>>> >> >> >> If you pay as you use the service (ie pay for coffee upfront),
>>> >> >> >> there's
>>> >> >> >> no need for PoP. Please see the Motivation section. But you are
>>> >> >> >> right
>>> >> >> >> that you must have the wallet(s) that paid at hand when you
>>> issue a
>>> >> >> >> PoP.
>>> >> >> >>
>>> >> >> >> >
>>> >> >> >> > Track payments, don't try to assign identities to payers.
>>> >> >> >>
>>> >> >> >> Please elaborate, I don't understand what you mean here.
>>> >> >> >
>>> >> >> >
>>> >> >> > I think that is a mistake. You should not assume that the wallet
>>> who
>>> >> >> > held
>>> >> >> > the coins is the payer/buyer. That's what I said earlier; you're
>>> >> >> > implicitly
>>> >> >> > creating an identity (the one who holds these keys) based on the
>>> >> >> > transaction. This seems fundamentally wrong to me, and not
>>> necessary.
>>> >> >> > The
>>> >> >> > receiver should not care who paid or how, he should care what was
>>> >> >> > payed
>>> >> >> > for.
>>> >> >>
>>> >> >> You are saying that it's a problem that the wallet used to pay,
>>> must
>>> >> >> also be used to issue the PoP? That may very well be a problem in
>>> some
>>> >> >> cases. People using PoP should of course be aware of it's
>>> limitations
>>> >> >> and act accordingly, i.e. don't pay for concert tickets for a
>>> friend
>>> >> >> and expect your friend to be able to enter the arena with her
>>> wallet.
>>> >> >> As Tom Harding noted, it is possible to transfer keys to your
>>> friend's
>>> >> >> wallet, but that might not be desirable if those keys are also used
>>> >> >> for other payments. Also that would weaken the security of an HD
>>> >> >> wallet, since a chain code along with a private key would reveal
>>> all
>>> >> >> keys in that tree. Another solution is that your friend forwards
>>> the
>>> >> >> PoP request to your wallet, through twitter or SMS, and you send
>>> the
>>> >> >> PoP for her. Maybe that forwarding mechanism can be built into
>>> wallets
>>> >> >> and automated so that the wallet automatically suggests to sign the
>>> >> >> PoP for your friend. This is probably something to investigate
>>> >> >> further, but not within the scope of this BIP.
>>> >> >>
>>> >> >> Of course the simplest solution would be to send money to your
>>> friend
>>> >> >> first so that she can pay for the ticket from her own wallet, but
>>> >> >> that's not always feasible.
>>> >> >>
>>> >> >> >
>>> >> >> > The easiest solution to this IMHO would be an extension to the
>>> >> >> > payment
>>> >> >> > protocol that gives you (or your wallet) a token in return for
>>> >> >> > paying,
>>> >> >> > and
>>> >> >> > that knowledge of that token is used to gain access to the
>>> services
>>> >> >> > you
>>> >> >> > provide.
>>> >> >> >
>>> >> >>
>>> >> >> That token would then be reusable. Someone stealing it would be
>>> able
>>> >> >> to use it as much as she wants. That is what I want to avoid with
>>> PoP.
>>> >> >> The BIP proposal briefly mentions something like this in the
>>> >> >> rationale. I also had a discussion about this with Mike Hearn on
>>> this
>>> >> >> list on Mars 13 that I think covers most pros and cons of the
>>> >> >> different approaches.
>>> >> >>
>>> >> >> While your suggestion does indeed separate the transaction from the
>>> >> >> proof of payment, it also assumes that the token is held in the
>>> wallet
>>> >> >> that pays. Otherwise you would need to keep it in another safe
>>> place,
>>> >> >> remember it's reusable. Where would that be? How would you transfer
>>> >> >> that token to your friend?
>>> >> >>
>>> >> >> Thank you again for your comments. I appreciate it.
>>> >> >>
>>> >> >> Best regards,
>>> >> >> Kalle
>>> >> >>
>>> >> >> > --
>>> >> >> > Pieter
>>> >> >> >
>>>
>>
>>
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📅 Original date posted:2015-06-22 📝 Original message:Thank ...

2023-06-07T15:39:43Z

In reply to nevent1q…d4h5
_________________________

📅 Original date posted:2015-06-22
📝 Original message:Thank you!

A few questions/comments:

* In the specification, you refer to "t_start". I guess you mean "time_start"?

* Miners can, especially when close to a block doubling or shortly
after activation, to some extent manipulate max block size by
manipulating the time stamp in the block header within valid limits.
According to the pseudo code in the specification, the first and a
handful of subsequent blocks after activation could actually have
negative max block sizes due to this (depending on how you define the
% operator of the pseudo code). I haven't checked the reference
implementation, but I do think that the specification section should
explicitly handle this.

Regards,
Kalle

2015-06-22 20:18 GMT+02:00 Gavin Andresen <gavinandresen at gmail.com>:
> I promised to write a BIP after I'd implemented
> increase-the-maximum-block-size code, so here it is. It also lives at:
> https://github.com/gavinandresen/bips/blob/blocksize/bip-8MB.mediawiki
>
> I don't expect any proposal to please everybody; there are unavoidable
> tradeoffs to increasing the maximum block size. I prioritize implementation
> simplicity -- it is hard to write consensus-critical code, so simpler is
> better.
>
>
>
>
> BIP: ??
> Title: Increase Maximum Block Size
> Author: Gavin Andresen <gavinandresen at gmail.com>
> Status: Draft
> Type: Standards Track
> Created: 2015-06-22
>
> ==Abstract==
>
> This BIP proposes replacing the fixed one megabyte maximum block size with a
> maximum size that grows over time at a predictable rate.
>
> ==Motivation==
>
> Transaction volume on the Bitcoin network has been growing, and will soon
> reach the one-megabyte-every-ten-minutes limit imposed by the one megabyte
> maximum block size. Increasing the maximum size reduces the impact of that
> limit on Bitcoin adoption and growth.
>
> ==Specification==
>
> After deployment on the network (see the Deployment section for details),
> the maximum allowed size of a block on the main network shall be calculated
> based on the timestamp in the block header.
>
> The maximum size shall be 8,000,000 bytes at a timestamp of 2016-01-11
> 00:00:00 UTC (timestamp 1452470400), and shall double every 63,072,000
> seconds (two years, ignoring leap years), until 2036-01-06 00:00:00 UTC
> (timestamp 2083190400). The maximum size of blocks in between doublings will
> increase linearly based on the block's timestamp. The maximum size of blocks
> after 2036-01-06 00:00:00 UTC shall be 8,192,000,000 bytes.
>
> Expressed in pseudo-code, using integer math:
>
> function max_block_size(block_timestamp):
>
> time_start = 1452470400
> time_double = 60*60*24*365*2
> size_start = 8000000
> if block_timestamp >= time_start+time_double*10
> return size_start * 2^10
>
> // Piecewise-linear-between-doublings growth:
> time_delta = block_timestamp - t_start
> doublings = time_delta / time_double
> remainder = time_delta % time_double
> interpolate = (size_start * 2^doublings * remainder) / time_double
> max_size = size_start * 2^doublings + interpolate
>
> return max_size
>
> ==Deployment==
>
> Deployment shall be controlled by hash-power supermajority vote (similar to
> the technique used in BIP34), but the earliest possible activation time is
> 2016-01-11 00:00:00 UTC.
>
> Activation is achieved when 750 of 1,000 consecutive blocks in the best
> chain have a version number with bits 3 and 14 set (0x20000004 in hex). The
> activation time will be the timestamp of the 750'th block plus a two week
> (1,209,600 second) grace period to give any remaining miners or services
> time to upgrade to support larger blocks. If a supermajority is achieved
> more than two weeks before 2016-01-11 00:00:00 UTC, the activation time will
> be 2016-01-11 00:00:00 UTC.
>
> Block version numbers are used only for activation; once activation is
> achieved, the maximum block size shall be as described in the specification
> section, regardless of the version number of the block.
>
>
> ==Rationale==
>
> The initial size of 8,000,000 bytes was chosen after testing the current
> reference implementation code with larger block sizes and receiving feedback
> from miners stuck behind bandwidth-constrained networks (in particular,
> Chinese miners behind the Great Firewall of China).
>
> The doubling interval was chosen based on long-term growth trends for CPU
> power, storage, and Internet bandwidth. The 20-year limit was chosen because
> exponential growth cannot continue forever.
>
> Calculations are based on timestamps and not blockchain height because a
> timestamp is part of every block's header. This allows implementations to
> know a block's maximum size after they have downloaded it's header, but
> before downloading any transactions.
>
> The deployment plan is taken from Jeff Garzik's proposed BIP100 block size
> increase, and is designed to give miners, merchants, and
> full-node-running-end-users sufficient time to upgrade to software that
> supports bigger blocks. A 75% supermajority was chosen so that one large
> mining pool does not have effective veto power over a blocksize increase.
> The version number scheme is designed to be compatible with Pieter's
> Wuille's proposed "Version bits" BIP.
>
> TODO: summarize objections/arguments from
> http://gavinandresen.ninja/time-to-roll-out-bigger-blocks.
>
> TODO: describe other proposals and their advantages/disadvantages over this
> proposal.
>
>
> ==Compatibility==
>
> This is a hard-forking change to the Bitcoin protocol; anybody running code
> that fully validates blocks must upgrade before the activation time or they
> will risk rejecting a chain containing larger-than-one-megabyte blocks.
>
> Simplified Payment Verification software is not affected, unless it makes
> assumptions about the maximum depth of a transaction's merkle branch based
> on the minimum size of a transaction and the maximum block size.
>
> ==Implementation==
>
> https://github.com/gavinandresen/bitcoinxt/tree/blocksize_fork
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

📅 Original date posted:2015-06-16 📝 Original message:Thank ...

2023-06-07T15:36:54Z

In reply to nevent1q…sux6
_________________________

📅 Original date posted:2015-06-16
📝 Original message:Thank you for your comments Pieter! Please find my answers below.

2015-06-16 16:31 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> On Mon, Jun 15, 2015 at 1:59 PM, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>>
>> 2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> I'm not sure if we will be able to support PoP with CoinJoin. Maybe
>> someone with more insight into CoinJoin have some input?
>
>
> Not really. The problem is that you assume a transaction corresponds to a
> single payment. This is true for simple wallet use cases, but not compatible
> with CoinJoin, or with systems that for example would want to combine
> multiple payments in a single transaction.
>

Yes, you are right. It's not compatible with CoinJoin and the likes.

>
> 48 bits seems low to me, but it does indeed solve the problem. Why not 128
> or 256 bits?

The nonce is limited because of the OP_RETURN output being limited to
40 bytes of data: 2 bytes version, 32 bytes txid, 6 bytes nonce.

>
>> > Why does anyone care who paid? This is like walking into a coffeshop,
>> > noticing I don't have money with me, let me friend pay for me, and then
>> > have
>> > the shop insist that I can't drink it because I'm not the buyer.
>>
>> If you pay as you use the service (ie pay for coffee upfront), there's
>> no need for PoP. Please see the Motivation section. But you are right
>> that you must have the wallet(s) that paid at hand when you issue a
>> PoP.
>>
>> >
>> > Track payments, don't try to assign identities to payers.
>>
>> Please elaborate, I don't understand what you mean here.
>
>
> I think that is a mistake. You should not assume that the wallet who held
> the coins is the payer/buyer. That's what I said earlier; you're implicitly
> creating an identity (the one who holds these keys) based on the
> transaction. This seems fundamentally wrong to me, and not necessary. The
> receiver should not care who paid or how, he should care what was payed for.

You are saying that it's a problem that the wallet used to pay, must
also be used to issue the PoP? That may very well be a problem in some
cases. People using PoP should of course be aware of it's limitations
and act accordingly, i.e. don't pay for concert tickets for a friend
and expect your friend to be able to enter the arena with her wallet.
As Tom Harding noted, it is possible to transfer keys to your friend's
wallet, but that might not be desirable if those keys are also used
for other payments. Also that would weaken the security of an HD
wallet, since a chain code along with a private key would reveal all
keys in that tree. Another solution is that your friend forwards the
PoP request to your wallet, through twitter or SMS, and you send the
PoP for her. Maybe that forwarding mechanism can be built into wallets
and automated so that the wallet automatically suggests to sign the
PoP for your friend. This is probably something to investigate
further, but not within the scope of this BIP.

Of course the simplest solution would be to send money to your friend
first so that she can pay for the ticket from her own wallet, but
that's not always feasible.

>
> The easiest solution to this IMHO would be an extension to the payment
> protocol that gives you (or your wallet) a token in return for paying, and
> that knowledge of that token is used to gain access to the services you
> provide.
>

That token would then be reusable. Someone stealing it would be able
to use it as much as she wants. That is what I want to avoid with PoP.
The BIP proposal briefly mentions something like this in the
rationale. I also had a discussion about this with Mike Hearn on this
list on Mars 13 that I think covers most pros and cons of the
different approaches.

While your suggestion does indeed separate the transaction from the
proof of payment, it also assumes that the token is held in the wallet
that pays. Otherwise you would need to keep it in another safe place,
remember it's reusable. Where would that be? How would you transfer
that token to your friend?

Thank you again for your comments. I appreciate it.

Best regards,
Kalle

> --
> Pieter
>

📅 Original date posted:2015-06-15 📝 Original ...

2023-06-07T15:36:53Z

In reply to nevent1q…gzwe
_________________________

📅 Original date posted:2015-06-15
📝 Original message:2015-06-15 12:00 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
> I did misunderstand that. That changes things significantly.
>
> However, having paid is not the same as having had access to the input
> coins. What about shared wallets or coinjoin?

Wallets will have the same ability to make PoPs as they have in making
payments, see my motivation and rationale sections. CoinJoin is not
compatible with PoP, Luke-Jr brought that up a week ago:

"This appears to be incompatible with CoinJoin at least. Maybe there's some
clean way to avoid that by using
https://github.com/Blockstream/contracthashtool ?"

I'm not sure if we will be able to support PoP with CoinJoin. Maybe
someone with more insight into CoinJoin have some input?

>
> Also, if I understand correctly, there is no commitment to anything you're
> trying to say about the sender? So once I obtain a proof-of-payment from you
> about something you paid, I can go claim that it's mine?

I don't understand this. The pop includes a nonce randomly generated
by the server. If you're very lucky, 1/(2^48) per try, you can reuse a
pop.

>
> Why does anyone care who paid? This is like walking into a coffeshop,
> noticing I don't have money with me, let me friend pay for me, and then have
> the shop insist that I can't drink it because I'm not the buyer.

If you pay as you use the service (ie pay for coffee upfront), there's
no need for PoP. Please see the Motivation section. But you are right
that you must have the wallet(s) that paid at hand when you issue a
PoP.

>
> Track payments, don't try to assign identities to payers.

Please elaborate, I don't understand what you mean here.

Regards,
Kalle

>
> On Jun 15, 2015 11:35 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>> Hi Pieter!
>>
>> It is intended to be a proof that you *have paid* for something. Not
>> that you have the intent to pay for something. You cannot use PoP
>> without a transaction to prove.
>>
>> So, yes, it's just a proof of access to certain coins that you no longer
>> have.
>>
>> Maybe I don't understand you correctly?
>>
>> /Kalle
>>
>> 2015-06-15 11:27 GMT+02:00 Pieter Wuille <pieter.wuille at gmail.com>:
>> > Now that you have removed the outputs, I don't think it's even a intent
>> > of
>> > payment, but just a proof of access to certain coins.
>> >
>> > On Jun 15, 2015 11:24 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>> >>
>> >> Hi all!
>> >>
>> >> I have made the discussed changes and updated my implementation
>> >> (https://github.com/kallerosenbaum/poppoc) accordingly. These are the
>> >> changes:
>> >>
>> >> * There is now only one output, the "pop output", of value 0.
>> >> * The sequence number of all inputs of the PoP must be set to 0. I
>> >> chose to set it to 0 for all inputs for simplicity.
>> >> * The lock_time of the PoP must be set to 499999999 (max block height
>> >> lock
>> >> time).
>> >>
>> >> The comments so far has been mainly positive or neutral. Are there any
>> >> major objections against any of the two proposals? If not, I will ask
>> >> Gregory Maxwell to assign them BIP numbers.
>> >>
>> >> The two BIP proposals can be found at
>> >> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
>> >> https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The
>> >> source
>> >> for the Proof of Payment BIP proposal is also in-lined below.
>> >>
>> >> A number of alternative names have been proposed:
>> >>
>> >> * Proof of Potential
>> >> * Proof of Control
>> >> * Proof of Signature
>> >> * Signatory Proof
>> >> * Popo: Proof of payment origin
>> >> * Pots: Proof of transaction signer
>> >> * proof of transaction intent
>> >> * Declaration of intent
>> >> * Asset-access-and-action-affirmation, AAaAA, or A5
>> >> * VeriBit
>> >> * CertiBTC
>> >> * VBit
>> >> * PayID
>> >>
>> >> Given this list, I still think "Proof of Payment" is the most
>> >> descriptive
>> >> to non-technical people.
>> >>
>> >> Regards,
>> >> Kalle
>> >>
>> >>
>> >> #################################################
>> >> <pre>
>> >> BIP: <BIP number>
>> >> Title: Proof of Payment
>> >> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>> >> Status: Draft
>> >> Type: Standards Track
>> >> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>> >> </pre>
>> >>
>> >> == Abstract ==
>> >>
>> >> This BIP describes how a wallet can prove to a server that it has the
>> >> ability to sign a certain transaction.
>> >>
>> >> == Motivation ==
>> >>
>> >> There are several scenarios in which it would be useful to prove that
>> >> you
>> >> have paid for something. For example:
>> >>
>> >> * A pre-paid hotel room where your PoP functions as a key to the door.
>> >> * An online video rental service where you pay for a video and watch it
>> >> on
>> >> any device.
>> >> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity.
>> >> During
>> >> this period you can upload new content to the sign whenever you like
>> >> using
>> >> PoP.
>> >> * Log in to a pay site using a PoP.
>> >> * A parking lot you pay for monthly and the car authenticates itself
>> >> using
>> >> PoP.
>> >> * A lottery where all participants pay to the same address, and the
>> >> winner
>> >> is selected among the transactions to that address. You exchange the
>> >> prize
>> >> for a PoP for the winning transaction.
>> >>
>> >> With Proof of Payment, these use cases can be achieved without any
>> >> personal information (user name, password, e-mail address, etc) being
>> >> involved.
>> >>
>> >> == Rationale ==
>> >>
>> >> Desirable properties:
>> >>
>> >> # A PoP should be generated on demand.
>> >> # It should only be usable once to avoid issues due to theft.
>> >> # It should be able to create a PoP for any payment, regardless of
>> >> script
>> >> type (P2SH, P2PKH, etc.).
>> >> # It should prove that you have enough credentials to unlock all the
>> >> inputs of the proven transaction.
>> >> # It should be easy to implement by wallets and servers to ease
>> >> adoption.
>> >>
>> >> Current methods of proving a payment:
>> >>
>> >> * In BIP0070, the PaymentRequest together with the transactions
>> >> fulfilling
>> >> the request makes some sort of proof. However, it does not meet 1, 2 or
>> >> 4
>> >> and it obviously only meets 3 if the payment is made through BIP0070.
>> >> Also,
>> >> there's no standard way to request/provide the proof. If standardized
>> >> it
>> >> would probably meet 5.
>> >> * Signing messages, chosen by the server, with the private keys used to
>> >> sign the transaction. This could meet 1 and 2 but probably not 3. This
>> >> is
>> >> not standardized either. 4 Could be met if designed so.
>> >>
>> >> If an input script type is P2SH, any satisfying script should do, just
>> >> as
>> >> if it was a payment. For M-of-N multisig scripts, that would mean that
>> >> any
>> >> set of M keys should be sufficient, not neccesarily the same set of M
>> >> keys
>> >> that signed the transaction. This is important because strictly
>> >> demanding
>> >> the same set of M keys would defeat the purpose of a multisig address.
>> >>
>> >> == Specification ==
>> >>
>> >> === Data structure ===
>> >>
>> >> A proof of payment for a transaction T, here called PoP(T), is used to
>> >> prove that one has ownership of the credentials needed to unlock all
>> >> the
>> >> inputs of T. It has the exact same structure as a bitcoin transaction
>> >> with
>> >> the same inputs as T and in the same order as in T, but with each
>> >> sequence
>> >> number set to 0. There is exactly one output, here called the pop
>> >> output,
>> >> with value 0. The pop output must have the following format:
>> >>
>> >> OP_RETURN <version> <txid> <nonce>
>> >>
>> >> {|
>> >> ! Field !! Size [B] !! Description
>> >> |-
>> >> | <version> || 2 || Version, little endian, currently 0x01
>> >> 0x00
>> >> |-
>> >> | <txid> || 32 || The transaction to prove
>> >> |-
>> >> | <nonce> || 6 || Random data
>> >> |}
>> >>
>> >> The lock_time of the PoP must be set to 499999999 to prevent the PoP
>> >> from
>> >> being included in a block, should it appear on the bitcoin p2p network.
>> >> This
>> >> is also the reason for setting the sequence numbers to 0, since
>> >> sequence
>> >> number of ffffffff would make lock_time ineffective. This specification
>> >> demands that all input sequence numbers are 0, not just one of them,
>> >> which
>> >> would be sufficient to make lock_time effective. This is for simplicity
>> >> reasons.
>> >>
>> >> An illustration of the PoP data structure and its original payment is
>> >> shown below.
>> >>
>> >> <pre>
>> >> T
>> >> +------------------------------------------------+
>> >> |inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +------------------------------------------------+
>> >> |input0 1,ffffffff | 0,pay to A |
>> >> |input1 3,ffffffff | 2,OP_RETURN <some data> |
>> >> |input2 4,ffffffff | 1,pay to B |
>> >> | | 4,pay to C |
>> >> +------------------------------------------------+
>> >>
>> >> PoP(T)
>> >> +-------------------------------------------------------------+
>> >> | inputs | outputs |
>> >> | Value,Sequence | Value,Script |
>> >> +-------------------------------------------------------------+
>> >> |input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
>> >> |input1 3,00000000 | |
>> >> |input2 4,00000000 | |
>> >> +-------------------------------------------------------------+
>> >> | lock_time=499999999 |
>> >> +-------------------------------------------------------------+
>> >> </pre>
>> >>
>> >> The PoP is signed using the same signing process that is used for
>> >> bitcoin
>> >> transactions.
>> >>
>> >> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>> >> the PoP has reached the server, that PoP is useless since the server
>> >> will
>> >> generate a new nonce for every PoP request.
>> >>
>> >> === Process ===
>> >>
>> >> # A proof of payment request is sent from the server to the wallet. The
>> >> PoP request contains:
>> >> ## a random nonce
>> >> ## a destination where to send the PoP, for example a https URL
>> >> ## data hinting the wallet which transaction to create a proof for. For
>> >> example:
>> >> ##* txid, if known by the server
>> >> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>> >> payment)
>> >> ##* amount, label, message or other information from a BIP0021 URI
>> >> # The wallet identifies a transaction T, if possible. Otherwise it asks
>> >> the user to select among the ones that match the hints in 1.iii.
>> >> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>> >> sign it.
>> >> # The user confirms
>> >> # The UPoP(T) is signed by the wallet, creating PoP(T).
>> >> # The PoP is sent to the destination in 1.ii.
>> >> # The server receiving the PoP validates it and responds with “valid”
>> >> or
>> >> “invalid”.
>> >> # The wallet displays the response in some way to the user.
>> >>
>> >> '''Remarks:'''
>> >>
>> >> * The method of transferring the PoP request at step 1 is not specified
>> >> here. Instead that is specified in separate specifications. See [btcpop
>> >> scheme BIP](btcpop scheme BIP).
>> >> * The nonce must be randomly generated by the server for every new PoP
>> >> request.
>> >>
>> >> === Validating a PoP ===
>> >>
>> >> The server needs to validate the PoP and reply with "valid" or
>> >> "invalid".
>> >> That process is outlined below. If any step fails, the validation is
>> >> aborted
>> >> and "invalid" is returned:
>> >>
>> >> # Check the format of the PoP. It must pass normal transaction checks,
>> >> except that the inputs may already be spent.
>> >> # Check that lock_time is 499999999.
>> >> # Check that there is exactly one output. This output must have value 0
>> >> and conform to the OP_RETURN output format outlined above.
>> >> # Check that the nonce is the same as the one requested.
>> >> # Check that the inputs of the PoP are exactly the same as in
>> >> transaction
>> >> T, except that the sequence numbers must all be 0. The ordering of the
>> >> inputs must also be the same as in T.
>> >> # Run the scripts of all the inputs. All scipts must return true.
>> >> # Check that the txid in the PoP output is the transaction you actually
>> >> want proof for. If you don’t know exactly what transaction you want
>> >> proof
>> >> for, check that the transaction actually pays for the product/service
>> >> you
>> >> deliver.
>> >> # Return "valid".
>> >>
>> >> == Security considerations ==
>> >>
>> >> * Someone can intercept the PoP-request and change any parameter in it.
>> >> These can be mitigated by using secure connections. For example:
>> >> ** Pop destination - Stealing your PoP.
>> >> ** label - Trick you to sign an unintended pop or set a label that your
>> >> wallet doesn't have any record for, resulting in a broken service.
>> >> Always
>> >> check the PoP before signing.
>> >> ** nonce - Your pop will not validate on server.
>> >> * Someone can steal a PoP, for example by tampering with the PoP
>> >> request,
>> >> and try to use the service hoping to get a matching nonce. Probability
>> >> per
>> >> try: 1/(2^48). The server should have a mechanism for detecting a brute
>> >> force attack of this kind, or at least slow down the process by
>> >> delaying the
>> >> PoP request by some 100 ms or so.
>> >> * Even if a wallet has no funds it might still be valuable as a
>> >> generator
>> >> for PoPs. This makes it important to keep the security of the wallet
>> >> after
>> >> it has been emptied.
>> >> * Transaction malleability may cause the server to have another
>> >> transaction id for a payment than the client's wallet. In that case the
>> >> wallet will not be able to prove the transaction to the server. Wallets
>> >> should not rely on the transaction id of the outgoing transaction.
>> >> Instead
>> >> it should listen for the transaction on the network and put that in its
>> >> list
>> >> of transactions.
>> >>
>> >> == Reference implementation ==
>> >>
>> >> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>> >>
>> >> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>> >>
>> >> == References ==
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki
>> >> BIP0021]:
>> >> URI Scheme
>> >>
>> >> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki
>> >> BIP0070]:
>> >> Payment Protocol
>> >>
>> >> [[btcpop scheme BIP]]
>> >>
>> >> #########################################################
>> >>
>> >> 2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> > Thank you all for the feedback.
>> >> >
>> >> > I will change the data structure as follows:
>> >> >
>> >> > * There will be only one output, the "pop output", and no outputs
>> >> > from
>> >> > T will be copied to the PoP.
>> >> > * The pop output will have value 0.
>> >> > * The sequence number of all inputs of the PoP will be set to 0. I
>> >> > chose to set it to 0 for all inputs for simplicity.
>> >> > * The lock_time of the PoP is always set to 499999999.
>> >> >
>> >> > Any comments on this?
>> >> >
>> >> > /Kalle
>> >> >
>> >> > 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> >> >> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>> >> >>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se>
>> >> >>> wrote:
>> >> >>>
>> >> >>>> I'm open to changes here.
>> >> >>>
>> >> >>> I suggest:
>> >> >>>
>> >> >>> - Don't include any real outputs. They are redundant because the
>> >> >>> txid is
>> >> >>> already referenced.
>> >> >>
>> >> >> with the nLocktime solution, the copied outputs are not needed.
>> >> >>
>> >> >>>
>> >> >>> - Start the proof script, which should be invalid, with a magic
>> >> >>> constant and
>> >> >>> include space for future expansion. This makes PoP's easy to
>> >> >>> identify
>> >> >>> and
>> >> >>> extend.
>> >> >>
>> >> >> I did remore the constant (a "PoP" literal ascii encoded string)
>> >> >> because it didn't add much. The recipient will expect a pop, so it
>> >> >> will simply treat it as one. I did add a 2 byte version field to
>> >> >> make
>> >> >> it extendable.
>> >> >>
>> >> >>>
>> >> >>> - "Proof of Potential"
>> >> >>
>> >> >> Noted :-)
>> >> >>
>> >> >> Thank you
>> >> >> /Kalle
>> >>
>> >>
>> >>
>> >> ------------------------------------------------------------------------------
>> >>
>> >> _______________________________________________
>> >> Bitcoin-development mailing list
>> >> Bitcoin-development at lists.sourceforge.net
>> >> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>> >>
>> >

📅 Original date posted:2015-06-06 📝 Original ...

2023-06-07T15:36:52Z

In reply to nevent1q…d3la
_________________________

📅 Original date posted:2015-06-06
📝 Original message:2015-06-06 17:32 GMT+02:00 Peter Todd <pete at petertodd.org>:
> On Sat, Jun 06, 2015 at 05:23:48PM +0200, Pieter Wuille wrote:
>> On Sat, Jun 6, 2015 at 5:18 PM, Luke Dashjr <luke at dashjr.org> wrote:
>>
>> > I also agree with Pieter, that this should *not* be so cleanly compatible
>> > with Bitcoin transactions. If you wish to share code, perhaps using an
>> > invalid opcode rather than OP_RETURN would be appropriate.
>>
>>
>> Using an invalid opcode would merely send funds into the void. It wouldn't
>> invalidate the transaction.
>
> Just set nLockTime to 500000000-1 and nSequence appropriately to make
> the transaction impossible to mine for the next 9500 years.

Actually, I suggested that on this list on april 27, but shortly after
rejected my own idea:

#######################
"Or a really high lock_time, but it would not make it invalid, just delayed."

Ok, this was a bad idea, since nodes would have to keep it in memory.
Please disregard that idea...
########################

Now I think I rejected it on based on a misunderstanding. Nodes will
not put them in their mempool unless it's value is near in time,
right? From the 0.9.0 release notes: "Accept nLockTime transactions
that finalize in the next block".

In that case this is a really nice option.

>
> Though I agree that this whole idea seems a bit dubious to me.
>
> --
> 'peter'[:-1]@petertodd.org
> 00000000000000000000dd919214b66444dcebb4aa0214c1ab7c8b3b633be71f
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>

📅 Original date posted:2015-06-15 📝 Original message:Hi ...

2023-06-07T15:36:50Z

In reply to nevent1q…s3jv
_________________________

📅 Original date posted:2015-06-15
📝 Original message:Hi all!

I have made the discussed changes and updated my implementation (
https://github.com/kallerosenbaum/poppoc) accordingly. These are the
changes:

* There is now only one output, the "pop output", of value 0.
* The sequence number of all inputs of the PoP must be set to 0. I
chose to set it to 0 for all inputs for simplicity.
* The lock_time of the PoP must be set to 499999999 (max block height lock
time).

The comments so far has been mainly positive or neutral. Are there any
major objections against any of the two proposals? If not, I will ask
Gregory Maxwell to assign them BIP numbers.

The two BIP proposals can be found at
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP and
https://github.com/kallerosenbaum/poppoc/wiki/btcpop-scheme-BIP. The source
for the Proof of Payment BIP proposal is also in-lined below.

A number of alternative names have been proposed:

* Proof of Potential
* Proof of Control
* Proof of Signature
* Signatory Proof
* Popo: Proof of payment origin
* Pots: Proof of transaction signer
* proof of transaction intent
* Declaration of intent
* Asset-access-and-action-affirmation, AAaAA, or A5
* VeriBit
* CertiBTC
* VBit
* PayID

Given this list, I still think "Proof of Payment" is the most descriptive
to non-technical people.

Regards,
Kalle

#################################################
<pre>
BIP: <BIP number>
Title: Proof of Payment
Author: Kalle Rosenbaum <kalle at rosenbaum.se>
Status: Draft
Type: Standards Track
Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
</pre>

== Abstract ==

This BIP describes how a wallet can prove to a server that it has the
ability to sign a certain transaction.

== Motivation ==

There are several scenarios in which it would be useful to prove that you
have paid for something. For example:

* A pre-paid hotel room where your PoP functions as a key to the door.
* An online video rental service where you pay for a video and watch it on
any device.
* An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
this period you can upload new content to the sign whenever you like using
PoP.
* Log in to a pay site using a PoP.
* A parking lot you pay for monthly and the car authenticates itself using
PoP.
* A lottery where all participants pay to the same address, and the winner
is selected among the transactions to that address. You exchange the prize
for a PoP for the winning transaction.

With Proof of Payment, these use cases can be achieved without any personal
information (user name, password, e-mail address, etc) being involved.

== Rationale ==

Desirable properties:

# A PoP should be generated on demand.
# It should only be usable once to avoid issues due to theft.
# It should be able to create a PoP for any payment, regardless of script
type (P2SH, P2PKH, etc.).
# It should prove that you have enough credentials to unlock all the inputs
of the proven transaction.
# It should be easy to implement by wallets and servers to ease adoption.

Current methods of proving a payment:

* In BIP0070, the PaymentRequest together with the transactions fulfilling
the request makes some sort of proof. However, it does not meet 1, 2 or 4
and it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof. If standardized it
would probably meet 5.
* Signing messages, chosen by the server, with the private keys used to
sign the transaction. This could meet 1 and 2 but probably not 3. This is
not standardized either. 4 Could be met if designed so.

If an input script type is P2SH, any satisfying script should do, just as
if it was a payment. For M-of-N multisig scripts, that would mean that any
set of M keys should be sufficient, not neccesarily the same set of M keys
that signed the transaction. This is important because strictly demanding
the same set of M keys would defeat the purpose of a multisig address.

== Specification ==

=== Data structure ===

A proof of payment for a transaction T, here called PoP(T), is used to
prove that one has ownership of the credentials needed to unlock all the
inputs of T. It has the exact same structure as a bitcoin transaction with
the same inputs as T and in the same order as in T, but with each sequence
number set to 0. There is exactly one output, here called the pop output,
with value 0. The pop output must have the following format:

OP_RETURN <version> <txid> <nonce>

{|
! Field !! Size [B] !! Description
|-
| <version> || 2 || Version, little endian, currently 0x01 0x00
|-
| <txid> || 32 || The transaction to prove
|-
| <nonce> || 6 || Random data
|}

The lock_time of the PoP must be set to 499999999 to prevent the PoP from
being included in a block, should it appear on the bitcoin p2p network.
This is also the reason for setting the sequence numbers to 0, since
sequence number of ffffffff would make lock_time ineffective. This
specification demands that all input sequence numbers are 0, not just one
of them, which would be sufficient to make lock_time effective. This is for
simplicity reasons.

An illustration of the PoP data structure and its original payment is shown
below.

<pre>
T
+------------------------------------------------+
|inputs | outputs |
| Value,Sequence | Value,Script |
+------------------------------------------------+
|input0 1,ffffffff | 0,pay to A |
|input1 3,ffffffff | 2,OP_RETURN <some data> |
|input2 4,ffffffff | 1,pay to B |
| | 4,pay to C |
+------------------------------------------------+

PoP(T)
+-------------------------------------------------------------+
| inputs | outputs |
| Value,Sequence | Value,Script |
+-------------------------------------------------------------+
|input0 1,00000000 | 0,OP_RETURN <version> <txid> <nonce> |
|input1 3,00000000 | |
|input2 4,00000000 | |
+-------------------------------------------------------------+
| lock_time=499999999 |
+-------------------------------------------------------------+
</pre>

The PoP is signed using the same signing process that is used for bitcoin
transactions.

The purpose of the nonce is to make it harder to use a stolen PoP; Once the
PoP has reached the server, that PoP is useless since the server will
generate a new nonce for every PoP request.

=== Process ===

# A proof of payment request is sent from the server to the wallet. The PoP
request contains:
## a random nonce
## a destination where to send the PoP, for example a https URL
## data hinting the wallet which transaction to create a proof for. For
example:
##* txid, if known by the server
##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
payment)
##* amount, label, message or other information from a BIP0021 URI
# The wallet identifies a transaction T, if possible. Otherwise it asks the
user to select among the ones that match the hints in 1.iii.
# The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
# The user confirms
# The UPoP(T) is signed by the wallet, creating PoP(T).
# The PoP is sent to the destination in 1.ii.
# The server receiving the PoP validates it and responds with “valid” or
“invalid”.
# The wallet displays the response in some way to the user.

'''Remarks:'''

* The method of transferring the PoP request at step 1 is not specified
here. Instead that is specified in separate specifications. See [btcpop
scheme BIP](btcpop scheme BIP).
* The nonce must be randomly generated by the server for every new PoP
request.

=== Validating a PoP ===

The server needs to validate the PoP and reply with "valid" or "invalid".
That process is outlined below. If any step fails, the validation is
aborted and "invalid" is returned:

# Check the format of the PoP. It must pass normal transaction checks,
except that the inputs may already be spent.
# Check that lock_time is 499999999.
# Check that there is exactly one output. This output must have value 0 and
conform to the OP_RETURN output format outlined above.
# Check that the nonce is the same as the one requested.
# Check that the inputs of the PoP are exactly the same as in transaction
T, except that the sequence numbers must all be 0. The ordering of the
inputs must also be the same as in T.
# Run the scripts of all the inputs. All scipts must return true.
# Check that the txid in the PoP output is the transaction you actually
want proof for. If you don’t know exactly what transaction you want proof
for, check that the transaction actually pays for the product/service you
deliver.
# Return "valid".

== Security considerations ==

* Someone can intercept the PoP-request and change any parameter in it.
These can be mitigated by using secure connections. For example:
** Pop destination - Stealing your PoP.
** label - Trick you to sign an unintended pop or set a label that your
wallet doesn't have any record for, resulting in a broken service. Always
check the PoP before signing.
** nonce - Your pop will not validate on server.
* Someone can steal a PoP, for example by tampering with the PoP request,
and try to use the service hoping to get a matching nonce. Probability per
try: 1/(2^48). The server should have a mechanism for detecting a brute
force attack of this kind, or at least slow down the process by delaying
the PoP request by some 100 ms or so.
* Even if a wallet has no funds it might still be valuable as a generator
for PoPs. This makes it important to keep the security of the wallet after
it has been emptied.
* Transaction malleability may cause the server to have another transaction
id for a payment than the client's wallet. In that case the wallet will not
be able to prove the transaction to the server. Wallets should not rely on
the transaction id of the outgoing transaction. Instead it should listen
for the transaction on the network and put that in its list of transactions.

== Reference implementation ==

[https://github.com/kallerosenbaum/poppoc poppoc on GitHub]

[https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]

== References ==

[https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
URI Scheme

[https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
Payment Protocol

[[btcpop scheme BIP]]

#########################################################

2015-06-06 23:25 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> Thank you all for the feedback.
>
> I will change the data structure as follows:
>
> * There will be only one output, the "pop output", and no outputs from
> T will be copied to the PoP.
> * The pop output will have value 0.
> * The sequence number of all inputs of the PoP will be set to 0. I
> chose to set it to 0 for all inputs for simplicity.
> * The lock_time of the PoP is always set to 499999999.
>
> Any comments on this?
>
> /Kalle
>
> 2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
>> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>>
>>>> I'm open to changes here.
>>>
>>> I suggest:
>>>
>>> - Don't include any real outputs. They are redundant because the txid
is
>>> already referenced.
>>
>> with the nLocktime solution, the copied outputs are not needed.
>>
>>>
>>> - Start the proof script, which should be invalid, with a magic
constant and
>>> include space for future expansion. This makes PoP's easy to identify
and
>>> extend.
>>
>> I did remore the constant (a "PoP" literal ascii encoded string)
>> because it didn't add much. The recipient will expect a pop, so it
>> will simply treat it as one. I did add a 2 byte version field to make
>> it extendable.
>>
>>>
>>> - "Proof of Potential"
>>
>> Noted :-)
>>
>> Thank you
>> /Kalle
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📅 Original date posted:2015-06-06 📝 Original message:Thank ...

2023-06-07T15:36:50Z

In reply to nevent1q…ham2
_________________________

📅 Original date posted:2015-06-06
📝 Original message:Thank you all for the feedback.

I will change the data structure as follows:

* There will be only one output, the "pop output", and no outputs from
T will be copied to the PoP.
* The pop output will have value 0.
* The sequence number of all inputs of the PoP will be set to 0. I
chose to set it to 0 for all inputs for simplicity.
* The lock_time of the PoP is always set to 499999999.

Any comments on this?

/Kalle

2015-06-06 19:00 GMT+02:00 Kalle Rosenbaum <kalle at rosenbaum.se>:
> 2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
>> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>>
>>> I'm open to changes here.
>>
>> I suggest:
>>
>> - Don't include any real outputs. They are redundant because the txid is
>> already referenced.
>
> with the nLocktime solution, the copied outputs are not needed.
>
>>
>> - Start the proof script, which should be invalid, with a magic constant and
>> include space for future expansion. This makes PoP's easy to identify and
>> extend.
>
> I did remore the constant (a "PoP" literal ascii encoded string)
> because it didn't add much. The recipient will expect a pop, so it
> will simply treat it as one. I did add a 2 byte version field to make
> it extendable.
>
>>
>> - "Proof of Potential"
>
> Noted :-)
>
> Thank you
> /Kalle

📅 Original date posted:2015-06-06 📝 Original ...

2023-06-07T15:36:50Z

In reply to nevent1q…waln
_________________________

📅 Original date posted:2015-06-06
📝 Original message:2015-06-06 18:10 GMT+02:00 Tom Harding <tomh at thinlink.com>:
> On Jun 6, 2015 8:05 AM, "Kalle Rosenbaum" <kalle at rosenbaum.se> wrote:
>
>> I'm open to changes here.
>
> I suggest:
>
> - Don't include any real outputs. They are redundant because the txid is
> already referenced.

with the nLocktime solution, the copied outputs are not needed.

>
> - Start the proof script, which should be invalid, with a magic constant and
> include space for future expansion. This makes PoP's easy to identify and
> extend.

I did remore the constant (a "PoP" literal ascii encoded string)
because it didn't add much. The recipient will expect a pop, so it
will simply treat it as one. I did add a 2 byte version field to make
it extendable.

>
> - "Proof of Potential"

Noted :-)

Thank you
/Kalle

📅 Original date posted:2015-06-06 📝 Original ...

2023-06-07T15:36:49Z

In reply to nevent1q…q8hq
_________________________

📅 Original date posted:2015-06-06
📝 Original message:>> The idea is to simplify implementation. Existing software can be used
>> as is to sign and validate PoPs. But I do agree that it would be a
>> cleaner specification if we would make the PoP invalid as a
>> transaction. I'm open to changes here. I do like the idea to prepend a
>> constant string. But that would require changes in transaction signing
>> and validation code, wouldn't it?
>
>
> Yes, of course. An alternative is adding a 21M BTC output at the end, or
> bitflipping the txin prevout hashes, or another reversible transformation on
> the transaction data that is guaranteed to invalidate it.

If we do decide to make Pops invalid as transactions, there are a lot
of ways to do that. I guess the main question is if we should make
Pops invalid as transactions or not. So far I prefer to keep them
valid for the above reason.

>
> I think that the risk of asking people to sign something that is not an
> actual transaction, but could be used as one, is very scary.
>

I would feel comfortable doing it. It's just a matter of trusting your
wallet, which you already do with your ordinary transactions.

>>
>> > Also, I would call it "proof of transaction intent", as it's a
>> > commitment to
>> > a transaction and proof of its validity, but not a proof that an actual
>> > transaction took place, nor a means to prevent it from being double
>> > spent.
>>
>>
>> Naming is hard. I think a simpler name that explains what its main
>> purpose is (prove that you paid for something) is better than a name
>> that exactly tries to explain what it is.
>
>
> "Proof of Payment" indeed does make me think it's something that proves you
> paid. But as described, that is not what a PoP does. It proves the ability
> to create a particular transaction, and committing to it. There is no actual
> payment involved (plus, payment makes me think you're talking about BIP70
> payments, not simple Bitcoin transactions).
>
>>
>> "Proof of transaction
>> intent" does not help me understand what this is about. But I would
>> like to see more name suggestions. The name does not prevent people
>> from using it for other purposes, ie internet over telephone network.
>
>
> I don't understand why something like "Proof of Transaction Intent" would be
> incompatible with internet over telephone network either...
>

No, I meant that it's ok to call it Proof of Payment even though
people may use it for other stuff.

> --
> Pieter
>

📅 Original date posted:2015-06-06 📝 Original message:> ...

2023-06-07T15:36:48Z

In reply to nevent1q…zdrm
_________________________

📅 Original date posted:2015-06-06
📝 Original message:> What do you gain by making PoPs actually valid transactions? You could for
> example change the signature hashing algorithm (prepend a constant string,
> or add a second hashing step) for signing, rendering the signatures in a PoP
> unusable for actual transaction, while still committing to the same actual
> transaction. That would also remove the need for the OP_RETURN to catch
> fees.

The idea is to simplify implementation. Existing software can be used
as is to sign and validate PoPs. But I do agree that it would be a
cleaner specification if we would make the PoP invalid as a
transaction. I'm open to changes here. I do like the idea to prepend a
constant string. But that would require changes in transaction signing
and validation code, wouldn't it?

>
> Also, I would call it "proof of transaction intent", as it's a commitment to
> a transaction and proof of its validity, but not a proof that an actual
> transaction took place, nor a means to prevent it from being double spent.
>

Naming is hard. I think a simpler name that explains what its main
purpose is (prove that you paid for something) is better than a name
that exactly tries to explain what it is. "Proof of transaction
intent" does not help me understand what this is about. But I would
like to see more name suggestions. The name does not prevent people
from using it for other purposes, ie internet over telephone network.

Thank you
/Kalle

>
>
> On Sat, Jun 6, 2015 at 4:35 PM, Kalle Rosenbaum <kalle at rosenbaum.se> wrote:
>>
>> Hi
>>
>> Following earlier posts on Proof of Payment I'm now proposing the
>> following BIP (To read it formatted instead, go to
>> https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP).
>>
>> Regards,
>> Kalle Rosenbaum
>>
>> <pre>
>> BIP: <BIP number>
>> Title: Proof of Payment
>> Author: Kalle Rosenbaum <kalle at rosenbaum.se>
>> Status: Draft
>> Type: Standards Track
>> Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
>> </pre>
>>
>> == Abstract ==
>>
>> This BIP describes how a wallet can prove to a server that it has the
>> ability to sign a certain transaction.
>>
>> == Motivation ==
>>
>> There are several scenarios in which it would be useful to prove that you
>> have paid for something. For example:
>>
>> * A pre-paid hotel room where your PoP functions as a key to the door.
>> * An online video rental service where you pay for a video and watch it on
>> any device.
>> * An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
>> this period you can upload new content to the sign whenever you like using
>> PoP.
>> * Log in to a pay site using a PoP.
>> * A parking lot you pay for monthly and the car authenticates itself using
>> PoP.
>> * A lottery where all participants pay to the same address, and the winner
>> is selected among the transactions to that address. You exchange the prize
>> for a PoP for the winning transaction.
>>
>> With Proof of Payment, these use cases can be achieved without any
>> personal information (user name, password, e-mail address, etc) being
>> involved.
>>
>> == Rationale ==
>>
>> Desirable properties:
>>
>> # A PoP should be generated on demand.
>> # It should only be usable once to avoid issues due to theft.
>> # It should be able to create a PoP for any payment, regardless of script
>> type (P2SH, P2PKH, etc.).
>> # It should prove that you have enough credentials to unlock all the
>> inputs of the proven transaction.
>> # It should be easy to implement by wallets and servers to ease adoption.
>>
>> Current methods of proving a payment:
>>
>> * In BIP0070, the PaymentRequest together with the transactions fulfilling
>> the request makes some sort of proof. However, it does not meet 1, 2 or 4
>> and it obviously only meets 3 if the payment is made through BIP0070. Also,
>> there's no standard way to request/provide the proof. If standardized it
>> would probably meet 5.
>> * Signing messages, chosen by the server, with the private keys used to
>> sign the transaction. This could meet 1 and 2 but probably not 3. This is
>> not standardized either. 4 Could be met if designed so.
>>
>> If the script type is P2SH, any satisfying script should do, just like for
>> a payment. For M-of-N multisig scripts, that would mean that any set of M
>> keys should be sufficient, not neccesarily the same set of M keys that
>> signed the transaction. This is important because strictly demanding the
>> same set of M keys would undermine the purpose of a multisig address.
>>
>> == Specification ==
>>
>> === Data structure ===
>>
>> A proof of payment for a transaction T, here called PoP(T), is used to
>> prove that one has ownership of the credentials needed to unlock all the
>> inputs of T. It has the exact same structure as a bitcoin transaction with
>> the same inputs and outputs as T and in the same order as in T. There is
>> also one OP_RETURN output inserted at index 0, here called the pop output.
>> This output must have the following format:
>>
>> OP_RETURN <version> <txid> <nonce>
>>
>> {|
>> ! Field !! Size [B] !! Description
>> |-
>> | <version> || 2 || Version, little endian, currently 0x01 0x00
>> |-
>> | <txid> || 32 || The transaction to prove
>> |-
>> | <nonce> || 6 || Random data
>> |}
>>
>> The value of the pop output is set to the same value as the transaction
>> fee of T. Also, if the outputs of T contains an OP_RETURN output, that
>> output must not be included in the PoP because there can only be one
>> OP_RETURN output in a transaction. The value of that OP_RETURN output is
>> instead added to the value of the pop output.
>>
>> An illustration of the PoP data structure and its original payment is
>> shown below.
>>
>> <pre>
>> T
>> +----------------------------------------------+
>> |inputs | outputs |
>> | Value | Value Script |
>> +----------------------------------------------+
>> |input0 1 | 0 pay to A |
>> |input1 3 | 2 OP_RETURN <some data> |
>> |input2 4 | 1 pay to B |
>> | | 4 pay to C |
>> +----------------------------------------------+
>>
>> PoP(T)
>> +----------------------------------------------------------+
>> |inputs | outputs |
>> | Value | Value Script |
>> +----------------------------------------------------------+
>> |input0 1 | 3 OP_RETURN <version> <txid> <nonce> |
>> |input1 3 | 0 pay to A |
>> |input2 4 | 1 pay to B |
>> | | 4 pay to C |
>> +----------------------------------------------------------+
>> </pre>
>>
>> The PoP is signed using the same signing process that is used for bitcoin
>> transactions.
>>
>> The purpose of the nonce is to make it harder to use a stolen PoP; Once
>> the PoP has reached the server, that PoP is useless since the server will
>> generate a new nonce for every PoP request.
>>
>> Since a PoP is indistinguishable from a bitcoin transaction, there is a
>> risk that it, accidently or maliciously, enters the bitcoin p2p network. If
>> T is still unconfirmed, or if a reorg takes place, chances are that PoP(T)
>> ends up in a block, invalidating T. Therefore it is important that the
>> outputs of the PoP are the same as in T. The zero transaction fee in PoP(T)
>> is to minimize the incentives for miners to select PoP(T) for inclusion.
>>
>> === Process ===
>>
>> # A proof of payment request is sent from the server to the wallet. The
>> PoP request contains:
>> ## a random nonce
>> ## a destination where to send the PoP, for example a https URL
>> ## data hinting the wallet which transaction to create a proof for. For
>> example:
>> ##* txid, if known by the server
>> ##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
>> payment)
>> ##* amount, label, message or other information from a BIP0021 URL
>> # The wallet identifies a transaction T, if possible. Otherwise it asks
>> the user to select among the ones that match the hints in 1.iii.
>> # The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
>> sign it.
>> # The user confirms
>> # The UPoP(T) is signed by the wallet, creating PoP(T).
>> # The PoP is sent to the destination in 1.ii.
>> # The server receiving the PoP validates it and responds with “valid” or
>> “invalid”.
>> # The wallet displays the response in some way to the user.
>>
>> '''Remarks:'''
>>
>> * The method of transferring the PoP request at step 1 is not specified
>> here. Instead that is specified in separate specifications. See [btcpop
>> scheme BIP](btcpop scheme BIP).
>> * The nonce must be randomly generated by the server for every new PoP
>> request.
>>
>> === Validating a PoP ===
>>
>> The server needs to validate the PoP and reply with "valid" or "invalid".
>> That process is outlined below. If any step fails, the validation is aborted
>> and "invalid" is returned:
>>
>> # Check the format of the PoP. It must pass normal transaction checks,
>> except that the inputs may already be spent.
>> # Check the PoP output at index 0. It must conform to the OP_RETURN output
>> format outlined above.
>> # Check that the rest of the outputs exactly corresponds to the outputs of
>> T and that they appear in the same order as in T. An exception to this is
>> that any OP_RETURN outputs of T must not be included in the PoP. All output
>> value from the OP_RETURN must instead be included in the PoP output.
>> # Check that the nonce is the same as the one you requested.
>> # Check that the inputs of the PoP are exactly the same as in transaction
>> T, and in the same order.
>> # Check the scripts of all the inputs, as would be done on a normal
>> transaction.
>> # Check that the txid in the PoP output is the transaction you actually
>> want proof for. If you don’t know exactly what transaction you want proof
>> for, check that the transaction actually pays for the product/service you
>> deliver.
>> # Return "valid".
>>
>> == Security considerations ==
>>
>> * Someone can intercept the PoP-request and change the PoP destination so
>> that the user sends the PoP to the bad actor.
>> * Someone can intercept the PoP-request and change for example the txid to
>> trick the user to sign a PoP for another transaction than the intended. This
>> can of course be avoided if the user is actually looking at the UPoP before
>> signing it. The bad actor could also set hints for a transaction, existing
>> or not, that the user didn’t make, resulting in a broken service.
>> * Someone can steal a PoP and try to use the service hoping to get a
>> matching nonce. Probability per try: 1/(2^48). The server should have a
>> mechanism for detecting a brute force attack of this kind, or at least slow
>> down the process by delaying the PoP request by some 100 ms or so.
>> * Even if a wallet has no funds it might still be valuable as a generator
>> for PoPs. This makes it important to keep the security of the wallet after
>> it has been emptied.
>> * Transaction malleability may cause the server to have another
>> transaction id than the wallet for the payment. In that case the wallet will
>> not be able to prove the transaction for the server. Wallets should not rely
>> on the transaction id of the outgoing transaction. Instead it should listen
>> for the transaction on the network and put that in its list of transactions.
>>
>> The first two issues are the same attack vector as for traditional, ie
>> BIP0021, bitcoin payments. They could be mitigated by using secure
>> connections.
>>
>> == Reference implementation ==
>>
>> [https://github.com/kallerosenbaum/poppoc poppoc on GitHub]
>>
>> [https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]
>>
>> == References ==
>>
>> [https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
>> URI Scheme
>>
>> [https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
>> Payment Protocol
>>
>> [[btcpop scheme BIP]]
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>>
>

📅 Original date posted:2015-06-06 📝 Original message:Hi ...

2023-06-07T15:36:46Z

In reply to nevent1q…q2j6
_________________________

📅 Original date posted:2015-06-06
📝 Original message:Hi

Following earlier posts on Proof of Payment I'm now proposing the following
BIP (To read it formatted instead, go to
https://github.com/kallerosenbaum/poppoc/wiki/Proof-of-Payment-BIP).

Regards,
Kalle Rosenbaum

<pre>
BIP: <BIP number>
Title: Proof of Payment
Author: Kalle Rosenbaum <kalle at rosenbaum.se>
Status: Draft
Type: Standards Track
Created: <date created on, in ISO 8601 (yyyy-mm-dd) format>
</pre>

== Abstract ==

This BIP describes how a wallet can prove to a server that it has the
ability to sign a certain transaction.

== Motivation ==

There are several scenarios in which it would be useful to prove that you
have paid for something. For example:

* A pre-paid hotel room where your PoP functions as a key to the door.
* An online video rental service where you pay for a video and watch it on
any device.
* An ad-sign where you pay in advance for e.g. 2 weeks exclusivity. During
this period you can upload new content to the sign whenever you like using
PoP.
* Log in to a pay site using a PoP.
* A parking lot you pay for monthly and the car authenticates itself using
PoP.
* A lottery where all participants pay to the same address, and the winner
is selected among the transactions to that address. You exchange the prize
for a PoP for the winning transaction.

With Proof of Payment, these use cases can be achieved without any personal
information (user name, password, e-mail address, etc) being involved.

== Rationale ==

Desirable properties:

# A PoP should be generated on demand.
# It should only be usable once to avoid issues due to theft.
# It should be able to create a PoP for any payment, regardless of script
type (P2SH, P2PKH, etc.).
# It should prove that you have enough credentials to unlock all the inputs
of the proven transaction.
# It should be easy to implement by wallets and servers to ease adoption.

Current methods of proving a payment:

* In BIP0070, the PaymentRequest together with the transactions fulfilling
the request makes some sort of proof. However, it does not meet 1, 2 or 4
and it obviously only meets 3 if the payment is made through BIP0070. Also,
there's no standard way to request/provide the proof. If standardized it
would probably meet 5.
* Signing messages, chosen by the server, with the private keys used to
sign the transaction. This could meet 1 and 2 but probably not 3. This is
not standardized either. 4 Could be met if designed so.

If the script type is P2SH, any satisfying script should do, just like for
a payment. For M-of-N multisig scripts, that would mean that any set of M
keys should be sufficient, not neccesarily the same set of M keys that
signed the transaction. This is important because strictly demanding the
same set of M keys would undermine the purpose of a multisig address.

== Specification ==

=== Data structure ===

A proof of payment for a transaction T, here called PoP(T), is used to
prove that one has ownership of the credentials needed to unlock all the
inputs of T. It has the exact same structure as a bitcoin transaction with
the same inputs and outputs as T and in the same order as in T. There is
also one OP_RETURN output inserted at index 0, here called the pop output.
This output must have the following format:

OP_RETURN <version> <txid> <nonce>

{|
! Field !! Size [B] !! Description
|-
| <version> || 2 || Version, little endian, currently 0x01 0x00
|-
| <txid> || 32 || The transaction to prove
|-
| <nonce> || 6 || Random data
|}

The value of the pop output is set to the same value as the transaction fee
of T. Also, if the outputs of T contains an OP_RETURN output, that output
must not be included in the PoP because there can only be one OP_RETURN
output in a transaction. The value of that OP_RETURN output is instead
added to the value of the pop output.

An illustration of the PoP data structure and its original payment is shown
below.

<pre>
T
+----------------------------------------------+
|inputs | outputs |
| Value | Value Script |
+----------------------------------------------+
|input0 1 | 0 pay to A |
|input1 3 | 2 OP_RETURN <some data> |
|input2 4 | 1 pay to B |
| | 4 pay to C |
+----------------------------------------------+

PoP(T)
+----------------------------------------------------------+
|inputs | outputs |
| Value | Value Script |
+----------------------------------------------------------+
|input0 1 | 3 OP_RETURN <version> <txid> <nonce> |
|input1 3 | 0 pay to A |
|input2 4 | 1 pay to B |
| | 4 pay to C |
+----------------------------------------------------------+
</pre>

The PoP is signed using the same signing process that is used for bitcoin
transactions.

The purpose of the nonce is to make it harder to use a stolen PoP; Once the
PoP has reached the server, that PoP is useless since the server will
generate a new nonce for every PoP request.

Since a PoP is indistinguishable from a bitcoin transaction, there is a
risk that it, accidently or maliciously, enters the bitcoin p2p network. If
T is still unconfirmed, or if a reorg takes place, chances are that PoP(T)
ends up in a block, invalidating T. Therefore it is important that the
outputs of the PoP are the same as in T. The zero transaction fee in PoP(T)
is to minimize the incentives for miners to select PoP(T) for inclusion.

=== Process ===

# A proof of payment request is sent from the server to the wallet. The PoP
request contains:
## a random nonce
## a destination where to send the PoP, for example a https URL
## data hinting the wallet which transaction to create a proof for. For
example:
##* txid, if known by the server
##* PaymentRequest.PaymentDetails.merchant_data (in case of a BIP0070
payment)
##* amount, label, message or other information from a BIP0021 URL
# The wallet identifies a transaction T, if possible. Otherwise it asks the
user to select among the ones that match the hints in 1.iii.
# The wallet creates an unsigned PoP (UPoP) for T, and asks the user to
sign it.
# The user confirms
# The UPoP(T) is signed by the wallet, creating PoP(T).
# The PoP is sent to the destination in 1.ii.
# The server receiving the PoP validates it and responds with “valid” or
“invalid”.
# The wallet displays the response in some way to the user.

'''Remarks:'''

* The method of transferring the PoP request at step 1 is not specified
here. Instead that is specified in separate specifications. See [btcpop
scheme BIP](btcpop scheme BIP).
* The nonce must be randomly generated by the server for every new PoP
request.

=== Validating a PoP ===

The server needs to validate the PoP and reply with "valid" or "invalid".
That process is outlined below. If any step fails, the validation is
aborted and "invalid" is returned:

# Check the format of the PoP. It must pass normal transaction checks,
except that the inputs may already be spent.
# Check the PoP output at index 0. It must conform to the OP_RETURN output
format outlined above.
# Check that the rest of the outputs exactly corresponds to the outputs of
T and that they appear in the same order as in T. An exception to this is
that any OP_RETURN outputs of T must not be included in the PoP. All output
value from the OP_RETURN must instead be included in the PoP output.
# Check that the nonce is the same as the one you requested.
# Check that the inputs of the PoP are exactly the same as in transaction
T, and in the same order.
# Check the scripts of all the inputs, as would be done on a normal
transaction.
# Check that the txid in the PoP output is the transaction you actually
want proof for. If you don’t know exactly what transaction you want proof
for, check that the transaction actually pays for the product/service you
deliver.
# Return "valid".

== Security considerations ==

* Someone can intercept the PoP-request and change the PoP destination so
that the user sends the PoP to the bad actor.
* Someone can intercept the PoP-request and change for example the txid to
trick the user to sign a PoP for another transaction than the intended.
This can of course be avoided if the user is actually looking at the UPoP
before signing it. The bad actor could also set hints for a transaction,
existing or not, that the user didn’t make, resulting in a broken service.
* Someone can steal a PoP and try to use the service hoping to get a
matching nonce. Probability per try: 1/(2^48). The server should have a
mechanism for detecting a brute force attack of this kind, or at least slow
down the process by delaying the PoP request by some 100 ms or so.
* Even if a wallet has no funds it might still be valuable as a generator
for PoPs. This makes it important to keep the security of the wallet after
it has been emptied.
* Transaction malleability may cause the server to have another transaction
id than the wallet for the payment. In that case the wallet will not be
able to prove the transaction for the server. Wallets should not rely on
the transaction id of the outgoing transaction. Instead it should listen
for the transaction on the network and put that in its list of transactions.

The first two issues are the same attack vector as for traditional, ie
BIP0021, bitcoin payments. They could be mitigated by using secure
connections.

== Reference implementation ==

[https://github.com/kallerosenbaum/poppoc poppoc on GitHub]

[https://github.com/kallerosenbaum/wallet Mycelium fork on GitHub]

== References ==

[https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki BIP0021]:
URI Scheme

[https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki BIP0070]:
Payment Protocol

[[btcpop scheme BIP]]
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