Wait, but the Signal Server does not need to store the contact graph, it stores only (some of) its vertices. Moxie wants to make it hard for somebody to learn a

Wait, but the Signal Server does not need to store the contact graph, it stores only (some of) its vertices. Moxie wants to make it hard for somebody to learn about the edges from the way clients ask whether a vertex is in signal's subgraph of the social graph. Why don't the clients simply use Tor to retrieve information about the numbers they're interested in? To avoid the server from using the time of the requests to correlate them, you could let the clients sleep a random amount of time in between requests, and sometimes request information they already have. Maybe you could even ask volunteers to spam the server with nonsense requests, so that the genuine requests are drowned in this noise.