Geotemporal Public Key Distribution

[Rich Jones]

This is a small, unfinished idea I had, but I'd be interested in hearing
any feedback anybody here might have to offer. Normally we talk about
cryptography to secure communications, but this is an idea rather about
verifying the authenticity of media.

[Quick backround: OpenWatch <https://openwatch.net> is a global citizen
media network using mobile phones as the basis for a free worldwide press.
We care very much about the authenticity of citizen media, and have
designed some systems
<https://github.com/Miserlou/CitizenMediaNotary>which attempt to
improve the verifiability of citizen media.]

The problem is that sometimes media artifacts are presented as a record of
a current event, when in fact they from different events. An example of
this was when images of a marathon race in Istanbul were presented as
images<http://twitchy.com/2013/06/01/debunked-photo-of-occupygezi-crowds-crossing-istanbul-bridge-is-a-fake/>of
the recent Occupy Gezi protests.

Now, imagine the globe divided into a grid coordinate system, say 100,000
units (or perhaps 232, if IP rather than physical address is to be used).
Based on their physical location, reporters can contact a server and are
assigned a key with which to sign or encrypt their media to. This then ties
a media object to a physical space. This can be further improved to include
both time and space by dividing a space-day into a number of units, suppose
1440, such that different keys would be handed out at different times of
the day, thus further tying a document to a moment in time as well.

Does anybody know if any systems like this have ever been discussed or
designed in the past? I suppose this is somewhat similar to the RSA-keyfob
system, although this allows for anonymous access without pre-arrangement
as well.

R
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