当我们在升级的过程中出现如下报错信息
报错信息如下所示：

The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6

W: GPG error: http://mirrors.jevincanders.net/kali kali-rolling InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6

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.

真正的原因的是缺少公钥，但是查了好多资料都不行，最终都是以失败告终，可以使用以下方法进行解决

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys ED444FF07D8D0BF6

通过成功下载公钥之后，就可以使用完成更新
apt-get update
apt-get upgrade