最新的kali Linux源，解决apt update报错说没有数字签名

原因：

国内源的地址大部分都是http开头，这些地址早就无法使用。

解决方案：

wget archive.kali.org/archive-key.asc                 //下载签名
apt-key add archive-key.asc                               //安装签名

另外，需要kali Linux更换最新的源地址：

vim /etc/apt/sources.list

#官方源
deb http://http.kali.org/kali kali-rolling main contrib non-free non-free-firmware
deb-src http://http.kali.org/kali kali-rolling main contrib non-free non-free-firmware

#阿里云
deb https://mirrors.aliyun.com/kali kali-rolling main non-free contrib
deb-src https://mirrors.aliyun.com/kali kali-rolling main non-free contrib

#清华大学
deb https://mirrors.tuna.tsinghua.edu.cn/kali kali-rolling main non-free contrib
deb-src https://mirrors.tuna.tsinghua.edu.cn/kali kali-rolling main non-free contrib

#中科大
deb https://