[Cryptography] "The U.S. Military Quietly Turned GPS Into a Global ‘Numbers Station,’ Evidence Suggests"

[Jerry Leichter]

>> The headline, of course, doesn't quite match the actual article  This summary does:  "A random sequence in an innocuous GPS message field is likely encrypted traffic from the U.S. military's system for remotely updating cryptographic keys around the world."
>> 
>> https://www.404media.co/the-u-s-military-quietly-turned-gps-into-a-global-numbers-station-evidence-suggests/?ref=weekly-roundup-newsletter
> 
> Interesting, considering how easily GPS is jammed.
I'm not sure how important that is in this application.  The re-keying material is presumably repeated many times to ensure, even when no jamming is present, that the message gets through - many things block GPS signals, and any particular piece of equipment may simply be turned off.  And the signals are likely to make it through the jamming here and there.

The thing I wonder about is different.  The message field is only 176 bits long.  Not much room for effective authentication!  Getting your enemy to re-key to an invalid key would be a great attack.
                                                        -- Jerry