GSM encryption crack made public

“The schemes commonly used to encrypt GSM telephone calls, SMS
messages, and data transmissions have been theoretically broken for
years at both the protocol and cipher levels, but results presented
in Berlin at the 26th Chaos Communication Congress (26C3) on
December 27 demonstrate that a practical attack can be easily
implemented. Researchers unveiled cracking tables requiring just
two terabytes of disk space that can be used to look up a GSM
encryption key and decrypt a transmission. The tables were computed
on 40 commodity hardware PC nodes in just a few months’ time, and
are shared through Bittorrent. Furthermore, the presentation
explains that the more difficult practical task of intercepting and
capturing GSM calls can already be done with inexpensive radio
equipment and open source software.

“Background

“The cipher under attack is known as A5/1; it was invented by
the GSM Association in 1987. Due to the Cold War, A5/1 was deployed
only in Western Europe and the United States, and was accompanied
by a significantly weaker cipher called A5/2 for export to other
regions. The GSM protocol supported both A5/1 and A5/2, plus A5/0,
or unencrypted connections, a choice that left the protocol itself
vulnerable to attack.”

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