The Bluetooth is a wireless interface that enables electronic devices to establish short-range, ad-hoc wireless connections. This kind of short-range wireless networking is known as Wireless Personal Area Networks (WPAN). Because of its attractive features of small size, low cost, and low power, Bluetooth gains a world wide usage. It is embedded in many portable computing devices and considered as a good replacement for local wire connections. Since wireless data is inherently exposed to eavesdropping, the security and confidentiality is a central issue for wireless standard as well as Bluetooth. To maintain security and confidentiality of wireless packets, the Bluetooth system mainly relies on the Frequency Hopping mechanism to equivocate an adversary. By this technique, a wireless channel is accessed for transmitting a packet. For each wireless packet, a single channel is selected in a pseudo random way. This kind of randomness in channel selection makes it difficult for an eavesdropped to predict the next channel to be accessed. Hence, capturing Bluetooth wireless packets is a challenge. In this work, we investigate the Frequency Hopping sequence and specifically the hop selection kernel. We analyze the operation of the kernel hardware by partitioning it into three parts. Based on this modeling, we propose an attacking method for the hop selection kernel. The proposed method shows how to expose the clock value hidden in the kernel. This helps to predict Bluetooth hopping sequence and, hence, capturing Bluetooth wireless packet is possible.
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