Subject: Re: [Bitcoin-development] Payment Protocol: BIP 70, 71, 72

From: Mike Hearn <[email-masked]>
Date: Wed, 31 Jul 2013 10:59:37 +0200

Woo, huzzah :-)

Now the BIP draft is available and we know it all hangs together, I'm
hoping to (re)start implementation work in bitcoinj in the next month or
two. I'm currently trying to figure out which is more important,
deterministic wallets or payment protocol, but I think right now the
payment protocol would be easier to do and would benefit more from a second
implementation. HD wallets have already been shown interoperable.

Comments on BIP 70:

   "PaymentRequest messages larger than 50,000 bytes should be rejected by
the merchant's server, to mitigate denial-of-service attacks."

Do you mean "users wallet" here?

You could note in the motivation section two more motivations:

1) That the protocol can be a foundation on which other features are built
2) That it is required to assist hardware wallets when there is a virus on
the system

Perhaps note in the BIP that the merchant should not assume the
merchant_data field is trustworthy - malicious buyers could rewrite it as
they see fit. Point out that a good way to use this is to serialize server
state, signed by a merchant-only key, in the same way one might use an HTTP
cookie.

   "PaymentDetails.payment_url must be secure against man-in-the-middle
attacks that might alter Payment.refund_to (if using HTTP, it must be
TLS-protected).

This says "must", but what should a client do here if the payment URL is
not HTTPS? I suggest weakening this to "should", as sometimes TLS is
redundant (e.g. if you're sending to a Tor hidden service).

The PaymentACK message contains a copy of Payment, but the BIP doesn't say
what to do with it. I assume this means a client is free to ignore it and
rely on TCP state to figure out the payment/ack connection instead? It may
be worth noting that explicitly.

In the certificates section, you could observe that "validation" means
"verification that it correctly chains to a trusted root authority, where
trusted roots may be obtained from the operating system. If there is no
operating system, the Mozilla root store is recommended".

All the rest LGTM.
[edit<https://en.bitcoin.it/w/index.php?title=BIP_0070&action=edit&section=7>
]

On Wed, Jul 31, 2013 at 8:28 AM, Gavin Andresen <[email-masked]>wrote:

> I've turned the preliminary payment protocol spec into three BIPs:
>
> https://en.bitcoin.it/wiki/BIP_0070 : Network protocol / messages
> https://en.bitcoin.it/wiki/BIP_0071 : MIME types for the messages
> https://en.bitcoin.it/wiki/BIP_0072 : bitcoin: URI extension
>
> I expect the wallet-side implementation to be pulled into Bitcoin-Qt Real
> Soon:
>   https://github.com/bitcoin/bitcoin/pull/2539
>
> There is also a reference implementation of server-side code for
> generating payment requests in php and C++ :
>   https://github.com/gavinandresen/paymentrequest
>
> --
> --
> Gavin Andresen
>
>
>
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