exclusive vs. shared smart card access

[NIIBE Yutaka]

On 09/01/2015 04:23 PM, Simon Josefsson wrote:
> There is U2F too which is supported by Chrome (works in Debian Stable).

I didn't know that.  Is it implemented parallel to OpenPGPcard as a
feature in a single smartcard?  How does it work with Yubikey?

If it's implemented by another interface of USB device, it's simpler,
it can co-exist.

Well, I'd imagine that it is now somehow very frustrated for a user,
using OpenPGPcard and U2F simultaneously, if it's implemented as a
single smartcard.

This would be a use case where shared access is somehow required.

Is it possible for the application of U2F for Yubikey to communicate
to scdaemon (like Poldi and Scute)?  The reason why I ask is that I
think that OpenPGPcard assumes exclusive access to the card and
scdaemon holds information of card status, if there were
"another channel" to access the card, I don't know how I can implement it
correctly...


Or, I think that it is somehow easily possible to write an application
of U2F which communicates gpg-agent, so that a user can use an
authentication subkey for U2F.  For me, this sounds the way to go.
How do you think this direction?
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