A5/2: Meaning (information, definition, explanation, facts)

A5/2 is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol.

The cipher is based around a combination of three linear feedback shift registers with irregular clocking and a non-linear combiner.

In 1999, Ian Goldberg and David Wagner cryptanalyzed A5/2 in the same month it was published, and showed that it was extremely weak — so much so that low end equipment can probably break it in real time.