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Comment by jameslevy | Hacker News Reader

Are tools such as homomorphic encryption, differential privacy, etc. applicable here? There should be a way for users to control their location data, and opt-in to sharing it at times like this, and then opt-out later.

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Homomorphic encryption is not computationally practical and differential privacy relies on noise which is not ideal when (i) errors compound as is the case of contact tracing where each new node introduces many candidates for exposure and (ii) there is a high cost of false positives or negatives.

For those curious by the claim that homomorphic encryption is not computationally practical, Bruce Shneier has a great article on it

https://www.schneier.com/blog/archives/2009/07/homomorphic_e...

Perhaps this is a use case for a secure enclave, where location data is stored, a biometric authenticated authorization can be used for releasing it, and there is provably no backdoor for this feature to be used without the user's approval. I hope to see companies like AAPL address this in a way that solves for these types of situations without introducing draconian oversight capabilities.

Because my guess is that location will give you too may false positives if ppl realy use that system. I wonder if it would not be better to do sth like emitting colocation ble beacons with totp sequence and a random secret. If some is tested positive you release the secret or a even only a list of the emitted beacons in the relevant timeframe. Everyone can then check against the list they recorded. Does that make sense?

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