Bruce Schneier wrote a great piece on the unencrypted Predator drone video feeds, noting that the drones were built for a post-Soviet, pre-insurgent era and that encryption, in the case of a live feed, is more of a problem than a threat.
The problem is, the world has changed. Today’s insurgent adversaries don’t have KGB-level intelligence gathering or cryptanalytic capabilities. At the same time, computer and network data gathering has become much cheaper and easier, so they have technical capabilities the Soviets could only dream of. Defending against these sorts of adversaries doesn’t require military-grade encryption only where it counts; it requires commercial-grade encryption everywhere possible.
While I agree with him whole-heartedly – Bruce knows his stuff – this is a huge PR mess for drone warfare. Luckily, these are drones and drones don’t have feelings and I suspect that once insurgents notice that they’re on a drone’s live feed, it’s probably too late.