[Freedombox-discuss] Follow up to the FreedomBox 'bump/hi-five' challenge

Daniel Kahn Gillmor dkg at fifthhorseman.net
Fri Jun 24 01:29:42 UTC 2011

On 06/23/2011 08:58 PM, erik.e.harmon at gmail.com wrote:
> I think this is perfectly reasonable. My reason for going back to the nonce is, while qr codes can hold an unsigned 2048 bit public key, the qr code will be unwieldy and hard to photograph. Extra onscreen verifiable information is great, I just want to prevent huge qr codes if possible since I've had trouble with those.

sure. i think if both parties share some other local means of
communication, the QRCode could be as simple as containing the following
three items:

 0) an OpenPGP key fingerprint or message digest for all offered info
 1) a (list of) local address(es) of where to fetch the offered info
 2) an ephemeral symmetric encryption key (and a specification of the
symmetric algorithm, padding form, and mode used, if we can't settle on
a single standard)

However, if we don't want to assume that the alternate communications
mechanisms are present, we might also want to include the standard
vcard-type info as well (so various fallback forms, including offline
checks, etc, can be done later by the user).

Yes, a less-dense QRcode is ultimately easier to reliably display and
scan; however, having to show one simple QR code, then find that the
devices can't actually exchange data via these other mechanisms, then
trying again with a denser QR-code doesn't sound like it would be very
fun from the usability side of things.

I suggest we focus on the simple, universal usability case first:  a
VCard-type set of data with the OpenPGP fingerprint.

Then, if someone wants to work on extending that to include local
large-data-transmission (optionally with an ephemeral session key),
that'd be lovely.

But let's start with the simple case first: a device with a camera and a
connection to the upstream internet (which includes keyservers) and work
from there.


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