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Comment by oleganza | Hacker News Reader

Would you mind sharing what protocols you are working on that can benefit from a "lightweight cryptography"?

My impression from learning cryptography in the last 8 years is that cryptographic protocols are either exponentially secure, or any tiny weaknesses can be amplified into a complete break.

The only example of secure "intrapolynomial cryptography" [1] is Proof-of-Work, but it also requires work to be expended continuously. Not exactly a scheme for "underpowered devices".

[1] https://nakamotoinstitute.org/intrapolynomial-cryptography/

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That is why NIST is doing this; most IoT I am aware of, including ours, needs a very secure channel, but for a relative short(er) time. So if it takes 6 hours minimum to decrypt it without having the private key, that would be fine for us and most IoT (that I have seen anyway) but bad for most general purpose computing, where you want 'infinite time' security if you can get it. I think it is a different and undervalued market, resulting often in bad security practices because we have no alternatives. The MCUs we use cost cents and are measured in mhz speed and kbs memory. They do have cryptographic co units but those are not very fast either while generic crypto algos tend to demand more and more power to guarantee longer periods of being decrypted by bad actors.

Edit: note that we are using RSA and, lately, Ed25519, but it takes 5-6s for the heaviest Ops and that is simply way too long. It is however secure and it works, so if that is it than that is it, it is just overkill mostly for what we need.

What happens after 6 hours? Let's say I capture all the data from all the sensors and decrypt it with a 24 hr lag. I don't get a real-time info, but i collect all the patterns and whatever long-term data that's accidentally sent out.

The data needs to reach a server within that period (the real period is much shorter: 5 minutes currently, but it might be 1-2 hours in the future); if it comes in after that, the server will find it invalid and drop it. We currently have it completely secure (modern ECC for instance): we have created a hybrid which refreshes a low power latency/power private key using the traditional means which gives us windows long enough to have low latency and lower power usage while ensuring the encryption holds. Something globally accepted would be better obviously. We have many more prototypes of things we evaluated ourselves but need help (if you know someone with these credentials) with just to solve the latency and power consumption issue.

So the server and device securely agree on something like TOTP list (weak keys with expiration date), so intermediate data can be authenticated within those time windows? But if that applies to encryption too, then won't later bruteforced decryption pose a threat?

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