One of the most important parts of this investigation is based
on a smart attacker. The main concept of the attacker is to
break any security constraints of the communication between
Alice and Bob. The first step is to identify the transmission
channel. For that reason the 802.15.4 PHY multi-channel
implementation was used. Under this procedure the attacker
(Eve) scans the available channels until she finds the specific
transmitted channel. The next step is to try to decode the
transmitted 802.15.4 packets. Two possible scenarios may
happen. The first is when the communication between the
users is without any AES-128 encryption, so the attacker is
able to decode encrypted messages. The second case is when
Bob and Alice share a predefined AES key. In this scenario if
the attacker has stolen the shared key, she is able to decode
the messages. If she does not hold the key, she can destroy the
transmission by applying a jamming attack on the specific
channel. When Bob and Alice anticipate a jamming attack,
they change channel. In this case the attacker applies a multichannel
scan until she finds the transmitted channel. Finally,
a malicious person can always apply jamming attacks independently
whether there is encryption or not. Fig. 6 depicts
the flowchart model of the attacker.