Real Time Cryptanalysis of Bluetooth Encryption with Condition Masking

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Abstract

The Bluetooth standard authorized by IEEE 802.15.1 adopts the two-level E0 stream cipher to protect short range privacy in wireless networks. The best published attack on it at Crypto 2005 requires 238 on-line computations, 238 off-line computations and 233 memory (which amount to about 19-hour, 37-hour and 64GB storage in practice) to restore the original encryption key, given the first 24 bits of 223.8 frames. In this paper, we describe more threatening and real time attacks against two-level E0 based on condition masking, a new cryptanalytic technique that characterizes the conditional correlation attacks on stream ciphers. The idea is to carefully choose the condition to get better tradeoffs on the time/memory/data complexity curve. It is shown that if the first 24 bits of 222.7 frames is available, the secret key can be reliably found with 227 on-line computations, 221.1 off-line computations and 4MB memory. Our attacks have been fully implemented on one core of a single PC. It takes only a few seconds to restore the original encryption key. This is the best known-IV attack on the real Bluetooth encryption scheme so far.

This work was supported by the National Grand Fundamental Research 973 Program of China(Grant No. 2013CB338002), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA06010701), IIE’s Research Project on Cryptography (Grant No. Y3Z0016102) and the programs of the National Natural Science Foundation of China (Grant No. 60833008, 60603018, 61173134, 91118006, 61272476)