A5/1 protects the over-the-air voice stream in GSM. Details on the protocol and cryptosystem: http://everything2.org/user/Jetifi/writeups/GSM http://everything

A5/1 protects the over-the-air voice stream in GSM. Details on the protocol and cryptosystem: http://everything2.org/user/Jetifi/writeups/GSM http://everything2.org/user/Jetifi/writeups/GSM I don't think this is quite as big a deal as it's made out to be, since that A5/1 and /2 were both broken almost a decade ago, and most GSM providers have replaced these two ciphers with others since then. It might still be useful in places outside of Europe and the US though.