There's FHE, but that's probably an even more difficult technical challenge than doing everything locally
FHE is impossible. You cannot expect to compete on 100x more cost for the same service you provide (and there is no design for accelerated hardware (Tensor Core) on FHE).
FHE would be ideal. Relevant conversation from 6 months ago:
https://news.ycombinator.com/item?id=44601023
FHE is impossible. You cannot expect to compete on 100x more cost for the same service you provide (and there is no design for accelerated hardware (Tensor Core) on FHE).