The paper addresses (to a small extent) the problem of jamming spread-spectrum digital radio. Ideally, you want to focus your jamming effort on as small a wind

The paper addresses (to a small extent) the problem of jamming spread-spectrum digital radio. Ideally, you want to focus your jamming effort on as small a window as possible, in order to ensure you drown out the target source, but if you're channel-hopping[1,2], that's a much wider band you have to saturate. The sender and receiver (eventually) synchronise, and so they know where they're going to hop next, and can filter tightly around that channel. The biggest problems with this system seems to be: 1) trying to retrofit digital & encrypted comms into currently used bands, requiring all sorts of horrible compromises to make it work. 2) Real-time voice (along with those compromises, and 'intelligibility-driven error correction') requires them to use a less capable encryption method. Accepting degraded voice signals means they can't reliably use MAC to avoid replay attacks. 3) User training and device usability are terrible. Combined with cargo-cult security ideas (must change keys fast good!) are worse. [1] https://secure.wikimedia.org/wikipedia/en/wiki/Frequency-hopping_spread_spectrum https://secure.wikimedia.org/wikipedia/en/wiki/Frequency-hop... [2] https://secure.wikimedia.org/wikipedia/en/wiki/Direct-sequence_spread_spectrum https://secure.wikimedia.org/wikipedia/en/wiki/Direct-sequen...