Fully Homomorphic Encryption and the Dawn of a Truly Private Internet

Re:Fully Homomorphic Encryption and the Dawn of a Truly Priv... by littlecranky67 on Friday July 18, 2025 @02:36AM (#44601851)

While correct, that doesn't answer the question at all, though. If I have my address book submited into an FHE system and want to sort by name - how do you do that if the FHE system does not have access to cleartext names?

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Re:Fully Homomorphic Encryption and the Dawn of a Truly Priv... by barisozmen on Friday July 18, 2025 @02:45AM (#44601916)

You can do that by encrypting the names. You send encrypted names to the FHE-server, and then the server does necessary sorting computations on it.

The point of FHE is it can operate on gibberish-looking ciphertext, and when this ciphertext decrypted afterwards, the result is correct.

Indeed, there are those working on faster FHE sorting: https://eprint.iacr.org/2021/551.pdf

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Re:Fully Homomorphic Encryption and the Dawn of a Truly Priv... by gadders on Friday July 18, 2025 @04:55AM (#44602606)

Honestly it breaks my brain as well. I just have to take it on trust that it apparently works.

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Re:Fully Homomorphic Encryption and the Dawn of a Truly Priv... by Tryk on Friday July 18, 2025 @07:36AM (#44603569)

When comparing two ciphertexts A,B a FHE sorting function will output a sorted pair of two new ciphertexts:

E.g. FHE_SORT(A,B) -> (X,Y)

where Dec(X)<Dec(Y)

But without decoding, there's no way of knowing whether X (or Y) comes from A or B.

Source: II. D of https://eprint.iacr.org/2015/995.pdf

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Re:Fully Homomorphic Encryption and the Dawn of a Truly Priv... by dcow on Friday July 18, 2025 @10:11AM (#44604844)

It’s not that simple. The client has to send the server the comparison function.

To do anything practical the server usually needs to provide the client with gigabytes of per-client-key encrypted seed data.

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