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Comment by withinboredom | Hacker News Reader

A whole new encryption scheme that will change my world. I’ll share it here when it’s polished up.

It allows you to encrypt anything and can be decrypted by anyone after a certain point in the future has passed. It uses the new NMA announcements (signed timestamps) from the Galileo GPS satellites to “prove” the time has passed and generate the decryption key.

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I built a similar scheme for a class project, but relying on verifiable delay functions [1] to provide the time lock.

Might be something you’re interested in.

[1] https://eprint.iacr.org/2018/601.pdf

Indeed! It looks familiar until you get to the verification (very SNARKy).

Oooh i've always thought about this but never dug deeper into where can one get a signed proof of time. Would really like to see how this will go! I can see a lot of things built on it ("validated" Web Archive, press/betting market, etc).

Maybe the GPS timestamps will become the world standard, maybe it will not be. I assume the NMA announcements have a public key to verify/decrypt the message.

Yeah, the protocol looks really robust. It should also allow some protection against spoofing signals.

https://gssc.esa.int/navipedia/index.php/Galileo_Open_Servic...

How does it work? I can imagine a program that checks if it sees a correctly signed message of the right time, but that program would then have to decrypt the payload, and I don't know how the key for the payload could be derived from the as yet nonexistent timestamp.

It’s basically a SNARK (cryptographic program) where the verification program itself is part of the cypher text and instead of outputting 0 or 1, you get decryption.

Not sure of the use cases, but it sounds very cool!

Basically a digital time locked safe.

You could send something to a reporter and not even the NSA could open it until the appropriate time.

You could encrypt crypto-wallet keys with it and your heir can’t open them until after turning a certain age.

My use case: my wife or myself write a letter that can’t be opened until some point in the future. Every year, we delete the old letter and write a new one. This is “in case we die” so it’s addressed to loved ones. Right now, we can theoretically read each other’s letters if we wanted to, but this encryption doesn’t require us trusting each other, the service we host them on, or anything.

Well, I'm sure the NSA would have the Galileo private keys? Seems eminently useful

If that were true, potentially every intelligence agency on earth would have a copy and it would defeat the purpose of it since anyone could spoof gps signals. It seems entirely within Europe’s interest to keep it out of any other agency’s hands as it would defeat the purpose of it.

These sorts of agencies have a habit of getting their hands on things that other people didn't intend them to.

Well, hopefully they get into a habit of routinely rotating the key.

Would that not break your system though? I admit my lack of knowledge in public key infrastructure.

I just checked and it looks like[1] this happens at least once a year, specifically to guard against this kind of attack. It doesn’t break the chain of hashes though.

1: https://www.euspa.europa.eu/sites/default/files/calls_for_pr...

> Right now, we can theoretically read each other’s letters if we wanted to, but this encryption doesn’t require us trusting each other, the service we host them on, or anything.

Ah, yes, this enables the famous trustless relationship. :)

(I kid, I'm sure you have a lovely relationship, but the clash was too funny for me)

> [...] but this encryption doesn’t require us trusting each other [...]

Your wife has to trust your encryption system and its implementation.

We do trust each other, this is mostly born of a conversation last week. We were talking about extending it just beyond us, but our loved ones as well, and friends. Thus “require” in this sentence does not imply we do not trust each other (we do) but that it is not necessary to work. We aren’t worried about governments and corporations with too much processing power solving np-complete problems to read these letters, though that may be other people’s threat models.

Nice idea, but.. that's not possible.

Why do you think that? I’ve already successfully encrypted and decrypted messages, so I’m very well aware of how possible it is.

I am also skeptical, though I am no expert. SNARK are zero-knowledge proofs, they are intended to give a proof that a result was computed correctly, not prevent an unwanted computation altogether.

The fact that you can decrypt after the time passed is of course the easy part, preventing decryption before then is the problem.

Yeah, there’s no telling how secure it is. Works, yes. Easily circumventable, maybe, maybe not. There’s a lot of math involved and I’m by no means an expert at any of it or guaranteed to have implemented everything correctly. For my personal purposes it’s 100% secure unless you know wtf you are looking at (much like a one-time-pad). Once the code and algorithms are published, it’s only secure until someone breaks it.

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