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by Pxtl 3435 days ago
So what, you hash each word in the e-mail and search for the hash, and this returns which emails include those hashed words? Would that be horribly insecure? I guess it would be impossible to salt those hashes, and it probably risks defeating the whole crypto.
2 comments

https://en.wikipedia.org/wiki/Salt_(cryptography)

You wouldn't use a hashing algorithm to build the index. They are talking about an inverted index in a binary format, something like what lucene outputs. That binary index would be encrypted with a block cipher (AES, Blowfish) using a secret key and would then be stored on the server.

The mobile client comes along and downloads & decrypts the index in memory, searches it for some terms(s), the index returns 10 result, of which, the user selects one and the mobile client downloads and decrypts to show to the user.

> Would that be horribly insecure?

Yes.

> I guess it would be impossible to salt those hashes, and it probably risks defeating the whole crypto.

Exactly. (There are other problems too, but that one by itself is a show-stopper.)