[Cryptography] [FORGED] Crptographic ticket tape (fake news)
phill at hallambaker.com
Tue Jun 4 11:00:58 EDT 2019
On Tue, Jun 4, 2019 at 2:17 AM Peter Gutmann <pgut001 at cs.auckland.ac.nz>
> Danny Muizebelt <dannym at packetloss.at> writes:
> >In securing original footage from tampering would a ticker tape in the
> >background be viable? The tape would be timestamps encrypted with the
> >producer's private key.
> There has been endless work done on tamperproof (meaning within certain
> cryptographic assumptions) logging, if you want to secure surveillance
> you'd be far better using any of those schemes than trying something like
This is what blockchain was originally invented for at Bellcore. And it is
pretty much the only thing it IS good for.
You don't need proof of work or any of that nonsense because the base tech
is so resilient all by itself. The user chooses a notary and takes their
output token, hashes that with their content and presents that as an input.
They receive back a notary entry/tree that fixes their act of presenting
their input between the two dates. The security of this token depends only
on the assumption that the hash chain was secure when the token was created
and the notary has not defected.
To put the system beyond feasible possibility of tampering it suffices for
the notary to cross notarize with other notaries. A meta-notary has the
property that none of them can defect successfully without all of them
defecting. [I go into the details in a paper]
So with some fairly straightforward engineering, you end up with a series
of nested proofs with different degrees of trust:
Assuming the immediate notary did not defect - bound time to 1 minute
Assuming none of the 10 nearest neighbors did not defect - bound time to 1
Assuming no notary anywhere in the world did not defect - bound time to 1
A notary is proven untrustworthy if they ever sign two divergent outputs.
If we have Iran, Venezuela, France, the US and Canada operating national
notaries, there will be meta-notaries that bridge them. So while any notary
can defect at any time, they cannot maintain the defection for very long
without collusion by everyone else.
The meta notary system described here is provably at least as strong as any
other scheme (e.g. proof of work blockchains) because you can always absorb
their outputs as inputs. But it is in any case because proof of work alone
doesn't actually achieve finality. Any ledger based system falls if a
position of extreme solipsism is taken.
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