Pilot Randomization to Protect MIMO Secret Key Generation Systems Against Injection Attacks

In this letter, we investigate the problem of secret key generation under an injection attack, which refers to tampering of pilot signals over the air so that part of the shared randomness observed at the legitimate parties is controlled by the adversary. It has been shown that to launch such an attack, an adversary only needs one extra antenna, compared to the legitimate parties, in a single input single output (SISO) network. In this letter, we generalize this result for the multiple input multiple output (MIMO) case. Furthermore, we propose pilot randomization as a means to protect against injection attacks by reducing them to jamming attacks that constitute a less serious threat. Finally, we derive a closed-form expression for the secret key rate of the investigated MIMO setting.