In this paper, we carefully study both distinguishing and key-recovery attacks against Bluetooth two-level EO given many short frames. Based on a flaw in the resynchronization of Bluetooth EO, we are able to fully exploit the largest bias of the finite state machine inside EO for our attacks. Our key-recovery attack works with 2<sup>40</sup> simple operations given the first 24 bits of 2<sup>35</sup> frames. Compared with all existing attacks against two-level EO, this is the best one so far
