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Comment by anonporridge | Hacker News Reader

How does this establish that we can trust the oracles telling us what time it is?

The only way I could see this working very long term and for important data is by using the bitcoin blockchain (often called the timechain) as a clock that literally can't be cheated because the proof of work allows you to independently verify that some amount of real world energy and computational machines were consumed to lock in every block. Otherwise, how do you not end up with a Byzantine generals problem?

But maybe I lack imagination.

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This is based on a permissioned threshold network, so as long as there are never a threshold number of nodes that are malicious and as long as there is a threshold number of nodes that continue to operate, the network's liveness and security is guaranteed. Using Bitcoin as a cryptographic reference clock has been proposed in the past, but the good way of doing it is relying also on SNARKs and isn't really that practical from what I can tell: https://link.springer.com/content/pdf/10.1007/s10623-018-046...

From another comment: “Besides calculating verifiably random numbers, the computers will also decrypt content for anyone if you send it content encrypted to their public keys and the encrypted content contains a time range that includes the present.” That sounds like decryption would fail when the present time is after the specified time range.

Yeah, that's not exactly how it works. The drand nodes are publishing random beacons that are signed, that's the only thing the networks does. Publishing public verifiable randomness. But pairing-based cryptography allows us to do identity-based encryption and that's like magic, but basically we can rely on a message as a public key, and on a signature as a secret key, and that's how tlock works.

A Sybil attack seems like the most likely weakness then.

Why do we trust permissioned nodes to not get compromised or the permissioning body to not accidentally or intentionally let in malicious nodes?

Couldn't a few well placed gag orders by a sufficiently powerful government be enough to subvert the whole system in a non evident way?

It could, and that's why a solid threshold network should have nodes in different locations, jurisdictions, cloud providers, etc. and have a threshold that's high enough to avoid that risk.

Some GPS satellites are currently broadcasting the current time with a cryptographic hash to prove that the broadcast time is the actual time[1] and authenticate the satellite as not being tampered with. It's live right now. So, as long as you can use witness encryption to prove that the broadcasted hash and signal is after a certain time, you can have true time locked encryption.

The problem is that the witness encryption is extremely inefficient with today's knowledge.

So, as long as you can trust a space agency to broadcast the current time to the entire world, you'll be fine.

[1]: https://www.gsc-europa.eu/galileo/services/galileo-open-serv...

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