Algoritmo secreto de cifra en flujo empleado por el
sistema de telefonía móvil digital GSM (Global System for Mobile
Communications), para cifrar el enlace entre el terminal y la estación base.
NOTA. El algoritmo ya no es secreto. [CESID:1997]
A5/1 is a stream cipher used
to provide over-the-air communication privacy in the GSM cellular telephone
standard. It was initially kept secret, but became public knowledge through
leaks and reverse engineering. A number of serious weaknesses in the cipher
have been identified.
http://en.wikipedia.org/wiki/A5/1