You could create a QR based on the last block of BITCOIN blockchain. These way you do not rely on a private key and onyone can check and trust it.
Back story: https://www.coindesk.com/markets/2017/06/26/proof-of-life-vi...
The block in question (open "Click to see more" and look for the "Hash" field): https://etherscan.io/block/3930000
An irrefutable cryptographic timestamp is just that, irrefutable.
Sometimes courts make mistakes, but you can’t expect any useful precedent over something like this.
Also, because of lack of expertise courts may simply not want to deal with this kind of proof and thus not acknowledge it.
Courts lack expertise on almost every subject, I don’t think this logic can actually hold up.
Opentimestamps cannot be bruteforced, and there are no keys that could leak.
Bruteforcing would require for you to permanently take over the entire bitcoin network.
In math, sure, but he specifically asked about a court of law. Irrefutable in math doesn't mean admissible in court. Then there's the 1, 6, 12, or however many random people that decide the case; they likely need the math explained to them, and two sides get turns convincing them the other is wrong.
> Irrefutable in math doesn't mean admissible in court
What is that even supposed to mean? Why would (relevant) math not be admissible in court? Do you even know what these words mean?
If cryptographic timestamps are relevant and not against the rules of evidence, obviously they are admissible.
The defence successfully argued that MD5 was not totally reliable -- even though the chance of it being faked was absolutely tiny.
The real irony was that without the MD5, the photos would probably have been accepted just on the police assertion of chain of custody.
(I've been looking for this news story but unfortunately I can't find it at the moment)
[edit- found it] https://www.schneier.com/blog/archives/2005/08/the_md5_defen...
In fact the MD5 was known to be vulnerable - maybe. But it's still the case that adding MD5 made it less trustworthy!
The point of this website is that the server signs the timestamp. It's more than just a QR code with a time and date, it has some actual verification code.
the website has the exact same problem that you pointed out for the blockchain: you can screen capture a QR code and re-use it later.
Right on the page, it says this.
Maybe I am not understanding your point. Both the website and the blockchain strategy make it impossible for you to record video content and claim it happened in the future, but neither of them defend against recording after the timestamp happened.
The blockchain strategy does not require a centralized service, while the QR code requires the website to be up forever.
There's also a way to generate the codes offline using a certificate chain and a fingerprint (https://github.com/qrdate/qrdate#static-qr-date-v1-spec) which does not require a website, just a key store. It needs more specifying to be viable for real world use but it should be possible. Help is very welcome.
AFAIK, signing off a timestamp and offering a public key to prove the timestamp was signed then doesn't seem to add value other than unnecessary complexity. I guess if there is a specific time you're trying to prove the event happened after, this system would offer higher fidelity than others, but not all.
Nothing, which is amusing irony.
Using info from the the block is safer as you don't need to trust the host of the system.
The point (like showing a newspaper) is to prove the image / video was taken no earlier than that time.
That thought does does cast an additional possible funny interpretation on a photo I took of the adjacent street newspaper vending boxes of the two major Boston papers one day. The Boston Globe main headline was of a serious major news event. The Boston Globe above the fold was mostly filled with a photo of some political or sports figure, and a lowbrow muckraking headline about them. A funny (highly implausible) theory is that the Herald editor/publisher had needed to determine the front page for a paper issue, days or more into the future, such as for faking proof-of-life on/after a date, and then had to run that front page. :)
It always only proves that it wasn't taken before a certain date.
You can then also prove "not after" by timestamping the picture (having it signed by a RFC3161 timestamping authority or putting a hash on the blockchain).
If the signature involves a hash of a bitcoin block we don't have to trust the site owner to not sign future timestamps.
It is still a concept as there's no implementation of it besides the tests in the repo, so it would require further refining for production apps. For example with specifying key exchange formats, which we are looking at right now. Anyone with expertise in this field wanting to contribute is welcome!