[Cryptography] Best internet crypto clock

[Arnold Reinhold]

On Oct 8, 2014, at 12:55 AM, Peter Gutmann <pgut001 at cs.auckland.ac.nz> wrote:

> Arnold Reinhold <agr at me.com> writes:
> 
>> This conundrum suggests a need for a camera that cryptographically signs its images.
> 
> These already exist, and have been in use for many years:
> 
> http://www.canberra.com/products/safeguards_surveillance_seals/pdf/DCM-14-SS-C29203.pdf
> http://www.iaea.org/safeguards/symposium/2010/Documents/PapersRepository/2605737238931922303602.pdf
> 
> Peter.

Those are interesting examples, but intended for fixed mounting in nuclear surveillance situations and presumably very costly. I'm thinking of a much more portable device based on cell phone technology, with video, audio and additional sensors such as motion, compass, GPS (ok, that one's a deal breaker for the kidnapping market). And as a separate question, what can be done with, say, the newer iPhones, given their stronger security model.  For example, two adversarial parties could video and sign the same event with separate phones and then sign each others videos after inspecting them and concluding that each captured the intended information. One could bound the time of the videos by starting with a Nist Beacon value and ending with a time stamp from a service. 

Arnold Reinhold