Personally I like James Nicoll's definition of hard science fiction: it's hard SF if the author gives enough details that the reader can be _certain_ it wouldn't work.
1,162 karma · joined May 24, 2010
The client enumerates all the machines it can see on its local LAN, and for each one, assembles a list of information about it, probably something like IP address, machine name, assigned user, maybe MAC address, etc. Hash this using SHA256 or something (unlike the suggestion in the ZeroTier article about IP addresses, this approach has enough information that brute force reversal is out of the question). Assemble a list of, say, 20 of these hashes - the client's own hash is first, followed by the rest of the LAN. If you have less than 20 nodes, fill out the list with random numbers; if you have more than 20, include yourself and 19 others at random (it's important that you pick them at random, not just the first 19 in your LAN listing). Send the list to the server - this reveals nothing about your LAN to it.
The server compares the hash lists sent by clients. If any two lists have any hashes in common, send a message to each of the clients that sent those lists: "You seem to be on the same LAN as the client with hash XYZ." The client can then look up the hash in its local table, and try to contact the corresponding node. (The list intersection check is why it's important to pick your sample at random - the birthday paradox is now working for us, and there's a good chance of at least one match even if your LAN has hundreds of nodes.)
Anything else is going to give you a false negative sooner or later. Yeah, you can spend hours framing a complicated expression that carefully tests for exactly what the current bucket of RFCs specify, but you're guaranteed to run into an MTA somewhere that disagrees with you, and you can argue until the cows come home that you're right and they're wrong, but it's still you that's going to have to change to accommodate them in the end.
Now, though, it sounds as if Intel may be making the opposite mistake. The Larrabee/KnightsThingummy family was built around x86 cores to make it easier to port existing code to it, but now it looks like this time people really are willing to rewrite their code to work on GPGPUs after all.
But I'm not sure I'd trust Data-Trater with my database.
(Edited to add) The individual stars you can see when you zoom all the way in are the very brightest stars, mostly blue (O/B class) or red (K/M class) giants. For each star you can see, there are hundreds of smaller stars that you can't make out individually but contribute to the general background glow.