Pirate Radio: RF UWB SS SDR [was: Gatwick drones]

coderman coderman at protonmail.com
Sat Jan 12 10:16:06 PST 2019


> Imagine a person with a computer on a canonical hill, with an hyper-wideband SDR radio, spreading out over perhaps 100 MHz in bandwidth.  (unused UHF station bands?  Military frequency allocations?)  I'm thinking of a transmitter of 10-100 watts, which when spread over 100 MHz, is not particularly loud.

the problem with a singular transmitter is still the trivial location determination - you want to make that last hop hard to find.

previous discussions have suggested MIMO for beam forming / phased array signal emission that lets you do fancy things, like emulate a moving transmitter.  if the transmitter appears to be constantly moving, it's a much harder target :)

these systems used to be millions of dollars, and now they are merely thousands. (soon enough only hundreds of $?)

>  Conceivably,  depending on his transmit footprint, 1 million potential listener-computers  can hear his signal, also by SDR.  He receives data, presumably through VPN or TOR, etc, by means of a packet which is doubly-encrypted:  The operator decrypts by using his private key, revealing a still-encrypted packet that he then transmits by ultra-broadband, using a secret provided by the decrypted packet..  Anyone who can 'hear' his signal, and who knows the encoding secret, can decrypt the data, but it can only be further decrypted by some further key.  So, nobody knows who actually was the intended recipient.

this is getting into canonical zero knowledge protocols, albeit adapted for wireless mesh networks. if you search the literature for "zero knowledge wireless sensor network" you'll find a long tangle of research to devour in this domain...

> This amounts to anonymizing "the last 10 miles", making it essentially impossible to learn who is actually receiving this information.

one benefit of actual broadcast receivers is the ability to distribute a large amount of information to all simultaneously. in some protocols this can be a big advantage. Tor directory information for example, could be broadcast over digital video bands and then partitioning attacks against directory obviated.

bitcoin had discussed doing this for blockchain distribution in Norway, IIRC.

best regards,
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