"practical private information retrieval" For single-server PIR that is almost certainly an impossibility, since no matter what sort of techniques you use you

"practical private information retrieval" For single-server PIR that is almost certainly an impossibility, since no matter what sort of techniques you use you must scan the entire database on every request (there may be some batching that can be done if several requests are from the same user, but if you have millions of users that is not terribly helpful). Multi-server PIR is already practical, but deployment is a bit difficult: who will be the other server? How will you ensure the other server's database is synchronized with yours?