A5算法是一种序列密码，它是欧洲GSM标准中规定的加密算法，用于数字蜂窝移动电话的加密，加密从用户设备到基站之间的链路。A5算法包括很多种，主要为A5/1和A5/2。其中，A5/1为强加密算法，适用于欧洲地区；A5/2为弱加密算法，适用于欧洲以外的地区。-The GSM encryption algorithm, A5, is not much good. Its effective key length

is at most five bytes　and anyone with the time and energy to look for faster

attacks can find source code for it at the bottom of this post.



The politics of all this is bizarre. Readers may recall that there was a fuss

last year about whether GSM phones could be exported to the Middle East　the

official line then was that A5 was too good for the likes of Saddam Hussein.