OpenPGP card specification enhancement for ECDSA support

[NIIBE Yutaka]

On 2013-03-01 at 11:02 -0800, Andrey Jivsov wrote:
> Please consider using the compact representation of an ECC point: 
> http://tools.ietf.org/html/draft-jivsov-ecc-compact with the OpenPGP card.

Thank you very much.  I didn't know this document.  All that I had
known about compression was x + (1-bit of y).

It is good this will be mentioned in the update of RFC6090.

> ( I will say that it's unfortunate that RFC 6637 was specified to use 
> SEC format 04 | x | y. The reason is that at the time I didn't know 
> about all the benefits that a *single* format such as 
> http://tools.ietf.org/html/draft-jivsov-ecc-compact would bring. I plan 
> to remedy this with another draft. So, it's a heads up. Please consider 
> not using the SEC format. )

I'm not sure about existing smartcard implementations and their ECDSA
features.  Possibly, they already took the approach of uncompressed
format.  If it is easier for them to use the uncompressed format, I
think that it would make sense for OpenPGP card specification to allow
this SEC format.

Sure, I will use this compression format for Gnuk.  Key generation
for ECDSA has not yet implemented there.
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