> Private lookups of a plaintext database are possible and have been for a while now (5+ years?). The problem is it often requires some nontrivial preprocessing of the plaintext database, or in the worst case a linear scan of the entire database.

So that basically means that if a company has data that my program might want to use, the entirety of that data needs to be loaded into my program. Not quite feasible for something like the Google search index, which (afaik) doesn't even fit onto a single machine.

Also, while Google is fine with us doing searches, making the whole search index available to a homomorphic encrypted program is probably a quite different beast.

Which ultimately results in gigabytes of per-client-encrypted data needing to be downloaded, and regenerated and redownloaded every time the index is updated.