kali linux 2.0配置更新源後apt-get update 報錯

這個是我/etc/apt/sources.list的更新源：

1 deb http://http.kali.org/kali kali-rolling main contrib non-free
2 deb http://old.kali.org/kali sana main non-free contrib

配置好以後apt-get update報錯以下：

 1 root@kali:~# apt-get update
 2 Get:1 http://old.kali.org/kali sana InRelease [20.3 kB]                
 3 Get:2 http://mirrors.neusoft.edu.cn/kali kali-rolling InRelease [30.5 kB]
 4 Err:1 http://old.kali.org/kali sana InRelease                    
 5   The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
 6 Err:2 http://mirrors.neusoft.edu.cn/kali kali-rolling InRelease
 7   The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
 8 Reading package lists... Done
 9 W: GPG error: http://old.kali.org/kali sana InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
10 E: The repository 'http://old.kali.org/kali sana InRelease' is not signed.
11 N: Updating from such a repository can't be done securely, and is therefore disabled by default.
12 N: See apt-secure(8) manpage for repository creation and user configuration details.
13 W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://mirrors.neusoft.edu.cn/kali kali-rolling InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>

經google查找解決方式，獲得國外大佬給出的解決方案：

https://forums.kali.org/showthread.php?38858-apt-get-update-GPG-error-key-expired

1 apt-key adv --keyserver hkp://keys.gnupg.net --recv-keys 7D8D0BF6

再次apt-get update就沒問題了