Comment by gojomo

The server already has a full copy of (its subset of) Wikipedia.

Every query touches every byte of that snapshot, in the same way... but the homomorphic-encryption math distills that down to just the fragment the client requested.

And it does so without giving even the CPU executing that math any hint of what bytes/ranges/topics survive the math. The much-smaller – but still, at every server step, encrypted – result is then sent to the client, which performs the decryption.

It's moon-math magic.