当你更换源后出现以下报错信息

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.aliyun.com/kali kali-rolling InRelease: The following signatures couldnt be verified because the public key is not available: NO_PUBKEY ED65462EC8D5E4C5

W: Failed to fetch http://mirrors.aliyun.com/kali/dists/kali-rolling/InRelease  The following signatures couldnt be verified because the public key is not available: NO_PUBKEY ED65462EC8D5E4C5

W: Some index files failed to download. They have been ignored, or old ones used instead.

N: Repository Kali Linux changed its non-free component value from non-free to non-free non-free-firmware

N: More information about this can be found online at: https://www.kali.org/blog/non-free-firmware-transition/

说明是签名的问题。 这里只需要几步快速解决它

1. 去下载签名

wget archive.kali.org/archive-key.asc

2. 把下载的签名添加 

apt-key add archive-key.asc

这里报错其实是因为 权限太低了， 不是root权限  

使用sudo 就可以了

sudo apt-key add archive-key.asc

输入的密码为你当前用户的密码

显示ok 代表成功，去验证是否还会报错

再次输入更新源

sudo apt-get update

成功解决很简单的2步。