If it is possible to obtain to obtain the link for the communication between two devices, it is possible to impersonate one side of the link and eavesdrop the communications.

If it is possible to obtain the initialization key used by the devices an attacker could generate the link key and other encryption keys therefore allowing eavesdroping and man-in-the-middle attacks.

The initialisation key usually depends on a PIN, can be between 8 and 128bits, and often has a default value of Zero.

It is also possible to Offline guess the PIN.