3 ms·

This is actually a really tricky topic. Things that sound like they should give very good security, often don't in practice. The "hashed bag of words" techniq

This is actually a really tricky topic. Things that sound like they should give very good security, often don't in practice. The "hashed bag of words" technique that you describe here sounds an awful lot like some recent attempts at letting legacy systems search on encrypted data [1,2]. We took at look at this recently [3], and it turns out that mapping the word numbers back to the original words is actually a lot more doable than you'd think. [1] ShadowCrypt: Encrypted Web Applications for Everyone http://dl.acm.org/citation.cfm?doid=2660267.2660326 http://dl.acm.org/citation.cfm?doid=2660267.2660326 [2] Mimesis Aegis: A Mimicry Privacy Shield–A System’s Approach to Data Privacy on Public Cloud https://www.usenix.org/conference/usenixsecurity14/technical-sessions/presentation/lau https://www.usenix.org/conference/usenixsecurity14/technical... [3] The Shadow Nemesis: Inference Attacks on Efficiently Deployable, Efficiently Searchable Encryption https://www.sigsac.org/ccs/CCS2016/agenda/ https://www.sigsac.org/ccs/CCS2016/agenda/

bjterry 10y ago
Yeah, I definitely don't think that this would give you mathematically provable security, especially if you are including n-grams which would allow you to chain together sentences combined with a language model. How much that matters in practice depends on the dimensionality reduction. In the context of google I doubt if this is even much of a specific goal, since no matter what they train on, they actually have access to the source text if they want it.