Digital signatures allow authentication of content based on a secret held by the signing entity. Are there any existing schemes, proposals or even services for letting "location" or "time" sign the content?

Motivation: Time and space (i.e. geolocation) are fundamental variables in our lifes and their integration in digital signatures could be useful e.g. for impeding fake news or elaborating on new proof-of-** principles for the broader field of "blockchain"-like technologies.

Are there any existing third party services? Or are there even trustless approaches maybe based on distributed computing / p2p-networks / sealed hardware?

Edit 1: I now see there are already some topics dealing with centralized timestamping services (e.g. here). Thus, the emphasis of this topic should be more directed towards trustless approaches.

  • $\begingroup$ I think it would be possible to add a second signature to confirm the geolocation. But I think it would also be pretty easy to fake this, i.e. with the use of TOR it's possible configure at least the country from where the exit node should be... $\endgroup$ – AleksanderRas Jan 17 '19 at 13:18
  • $\begingroup$ There are "Trusted Timestamping" services, where trusted 3rd parties (usually backed by a certificate authority) provides timespamping of documents. $\endgroup$ – gusto2 Jan 17 '19 at 13:49
  • $\begingroup$ Are you asking the time and location information will be in the signature? $\endgroup$ – kelalaka Jan 17 '19 at 13:59
  • $\begingroup$ @AleksanderRas: I agree, localization using IP address is not safe. $\endgroup$ – mneg Jan 21 '19 at 11:36
  • $\begingroup$ gusto2: thank you, added that information to the post. kelalaka: yes, I think it would be convenient to put that information into or near to the signature so a second party could check for it somehow $\endgroup$ – mneg Jan 21 '19 at 11:43

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