[Cryptography] Comey: targeted ads => plaintext access

[Tony Arcieri]

On Sun, Sep 13, 2015 at 2:38 PM, Jerry Leichter <leichter at lrw.com> wrote:

> The plaintext itself *can* be protected by using an end-to-end encryption
> protocol.  That will prevent targeting of ads - and things like server-side
> searches.  (It doesn't provide the kind of security properties you'd
> probably really like to have, but that's another story.)
>

Both ad targeting and search are possible against ciphertext.

There are many schemes for searchable symmetric encryption. There's also
partially and fully homomorphic encryption (the latter being quite slow,
but capable of expressing arbitrary circuits):

https://eprint.iacr.org/2013/451.pdf

Allowing a potential attacker to compute things about your ciphertexts
(even if they can't tell specifically what they're computing) leaks some
information of course.

See for example the recent attacks against CryptDB:

http://research.microsoft.com/en-us/um/people/senyk/pubs/edb.pdf

-- 
Tony Arcieri
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