root@localhost:~# apt-get update
Get:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease [30.5 kB]
Err:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease
The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository devel@kali.org
Reading package lists... Done
W: GPG error: http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository devel@kali.org
E: The repository 'http://http.kali.org/kali kali-rolling InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@localhost:~#
root@localhost:~# apt-get update Get:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease [30.5 kB] Err:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository devel@kali.org Reading package lists... Done W: GPG error: http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository devel@kali.org E: The repository 'http://http.kali.org/kali kali-rolling InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. root@localhost:~#