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Date: Fri, 7 Mar 2014 12:01:15 +0100
Message-ID: <CANEZrP3sQWqjpt2vMS8paQvWM=Fn=jPkEOk9g_ZukM3Ouhkw=A@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Andreas Schildbach <andreas@schildbach.de>
Content-Type: multipart/alternative; boundary=089e0112cd322e9b9a04f4022cfe
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Instant / contactless payments
Precedence: list

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>
> Interesting side note: They recommend messages transmitted via NFC to
> not exceed 1 KB in order for a snappy experience. This (again) questions
> usage of bulky X.509 certificates in our payment request messages.
> Bitcoin Wallet currently does not sign payment requests, so I could not
> try how it would feel.


I think you could just put a signed PaymentRequest into an NFC tag and try
reading it from that. It's the same underlying radio tech so the transfer
speeds should be similar, I'd think.

Common X.509 certs are bigger than they need to be for sure, but a lot of
the bulk comes from the use of RSA rather than ECC. An RSA signature alone
can be 256 bytes! There's nothing that states you have to use RSA for
certificates and ECC certs are out there (Google uses one), but I think
they are harder to get hold of. I guess over time SSL will migrate to
mostly ECC (secp256r1) based certs.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #c=
cc solid;padding-left:1ex"><div class=3D"HOEnZb"><div class=3D"h5"><span st=
yle=3D"color:rgb(34,34,34)">Interesting side note: They recommend messages =
transmitted via NFC to</span><br>
</div></div>
not exceed 1 KB in order for a snappy experience. This (again) questions<br=
>
usage of bulky X.509 certificates in our payment request messages.<br>
Bitcoin Wallet currently does not sign payment requests, so I could not<br>
try how it would feel.</blockquote><div><br></div><div>I think you could ju=
st put a signed PaymentRequest into an NFC tag and try reading it from that=
. It&#39;s the same underlying radio tech so the transfer speeds should be =
similar, I&#39;d think.</div>
<div><br></div><div>Common X.509 certs are bigger than they need to be for =
sure, but a lot of the bulk comes from the use of RSA rather than ECC. An R=
SA signature alone can be 256 bytes! There&#39;s nothing that states you ha=
ve to use RSA for certificates and ECC certs are out there (Google uses one=
), but I think they are harder to get hold of. I guess over time SSL will m=
igrate to mostly ECC (secp256r1) based certs.</div>
</div></div></div>

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