WireLess keys Cars & Doors KeeLoq FAIL

[C]

Just saw this on arstechnica
Widely used keyless entry systems can be hacked in seconds with wallet-sized device.
$30

http://arstechnica.com/security/2015/08/meet-rolljam-the-30-device-that-jimmies-car-and-garage-doors/

C

[PA0PBZ]

The device contains two radios. The first jams the airwaves to prevent the lock from receiving the rolling code sent by the electronic key. Since the car or garage door doesn't unlock, a user almost certainly will press the lock or unlock button again. Once RollJam has collected the latter rolling code, it uses the second radio to broadcast the earlier rolling code to the lock. RollJam then stores the latter rolling code. Because the code was never received by the lock, it remains valid.

Right, but:

 - How does the device receive the first code while jamming the frequency so that the car does not receive it?
 - How does the device prevent the car from receiving the second code?
 

[C]

The electronic key transmits at max power
Distance is the opening here.
The receiver is expecting a digital signal.
The jamming could be as simple as broadband noise. This would raise the noise floor of the intended receiver, the electronic key would need to be closer to still function.
With the device creating the noise there exists the possibility of subtracting the noise out of what it receives. And the receiver could be better.

C