From: Jeff Garzik <jgarzik@bitpay•com>
To: Mike Hearn <mike@plan99•net>
Cc: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>,
Andreas Schildbach <andreas@schildbach•de>
Subject: Re: [Bitcoin-development] BIP72 amendment proposal
Date: Fri, 12 Sep 2014 10:15:21 -0400 [thread overview]
Message-ID: <CAJHLa0Px985E7NyhHVPRpLxXD6XDGhd_WwsbHNBaQZVMQwxTwA@mail.gmail.com> (raw)
In-Reply-To: <CANEZrP1iTfZxY915hzoAEApz1+wd_S9j5RCwVJCNFqQ_+DNTSQ@mail.gmail.com>
Indeed -- Every byte added to the QR code makes it more difficult to
be used in restaurants, pubs and other low-light conditions. BitPay
tested some of these scenarios.
Scannability is absolutely impacted.
On Fri, Sep 12, 2014 at 9:49 AM, Mike Hearn <mike@plan99•net> wrote:
> A few thoughts on this:
>
> (1) Base64 of SHA256 seems overkill. 256 bits of hash is a lot. The risk
> here is that a MITM intercepts the payment request, which will be typically
> requested just seconds after the QR code is vended. 80 bits of entropy would
> still be a lot and take a long time to brute force, whilst keeping QR codes
> more compact, which impacts scannability.
>
> (2) This should not be necessary in the common HTTPS context. The QR code
> itself is going to be fetched from some service, over HTTPS. I see no
> reasonable attacker that can MITM the request for the BIP70 message but not
> the request to get the QR code. Adding a hash makes QR codes more bloated
> and harder to scan, all on the assumption that HTTPS is broken in some odd
> way that we haven't actually ever seen in practice.
>
> (3) This can be useful in the Bluetooth context, but then again, we could
> also do things a different way by signing with the key in the first part of
> the URI, thus avoiding the need for a hash.
>
> I know I've been around the loop on this one with Andreas many times. But
> this BIP doesn't fix any actually existing problem in the previous spec. It
> exists because Andreas thinks SSL is useless. If SSL is useless we all have
> much bigger problems.
>
> ------------------------------------------------------------------------------
> Want excitement?
> Manually upgrade your production database.
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> _______________________________________________
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>
--
Jeff Garzik
Bitcoin core developer and open source evangelist
BitPay, Inc. https://bitpay.com/
next prev parent reply other threads:[~2014-09-12 14:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.341412.1410515709.2178.bitcoin-development@lists.sourceforge.net>
2014-09-12 10:11 ` Mark van Cuijk
2014-09-12 11:07 ` Andreas Schildbach
2014-09-12 13:49 ` Mike Hearn
2014-09-12 14:15 ` Jeff Garzik [this message]
2014-09-12 14:36 ` Andreas Schildbach
2014-09-12 15:25 ` Christophe Biocca
2014-09-12 15:33 ` Christophe Biocca
2014-09-12 15:37 ` Mike Hearn
2014-09-12 16:31 ` Mike Hearn
2014-09-12 18:43 ` Aaron Voisine
2014-09-15 7:43 ` Andreas Schildbach
2014-09-15 7:12 ` Andreas Schildbach
2014-09-12 15:36 ` Mike Hearn
[not found] <mailman.342174.1410547421.2163.bitcoin-development@lists.sourceforge.net>
2014-09-12 20:59 ` Mark van Cuijk
2014-09-13 8:53 ` Wladimir
2014-09-12 9:29 Andreas Schildbach
2014-09-12 9:55 ` Wladimir
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