he 1.28-second period, it changes to another channel intercepted communications, since only the intended frequency. Since the master is sending bursts over the recipient can decipher them. Both authentication and whole inquiry frequency range at a fast rate-two bursts implementation routines are implemented in the same per 1250 microsecond interval-there's a high probabil- way. They involve the creation of secret keys that are ity the scanning device will catch at least one of the generated from the unique Bluetooth device address, a transmissions while it remains on a single frequency. If PIN (personal identification number) code, and a random that channel happens to be blocked by interference, then number derived from a random or pseudo-random pro- the slave will receive a transmission after one of its cess in the Bluetooth unit. Random numbers and keys are subsequent frequency changes. When the slave does hear changed frequently. The length of a key is a measure of the a signal, it responds during the next slot with a special difficulty of cracking a code. Authentication in Bluetooth packet called FHS (frequency hop synchronization) in uses a 128-bit key, but the key size for encryption is which is contained the slave's Bluetooth address and variable and may range from 8 to 128 bits. state of its internal clock register. The master does not respond but notes the slave's particulars and continues inquiries until it has listed the available devices in its Inquiry and paging range. The protocol has provisions for avoiding collisions from more than one scanning device that may have A distinguishing feature of Bluetooth is its ad hoc pro- detected a master on the same frequency and at the same tocol and connections are often required between devices time. that have no previous knowledge of their nature or ad- The master makes the actual connection with a new dress. Also, Bluetooth networks are highly volatile, in device appearing in its inquiry list using the page routine. comparison to WLAN for example, and connec