Invalid signature for Kali Linux

Hi I'm a Kali Linus virgin. My first command in terminal was to check for updates:

apt-get update
this is what I got as a response

root@kali:~# apt-get update
Get:1 http://ftp.hands.com/kali kali-rolling InRelease [30.5 kB]
Err:1 http://ftp.hands.com/kali kali-rolling InRelease
The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
Fetched 30.5 kB in 1s (25.6 kB/s)
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ftp.hands.com/kali kali-rolling InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
W: Failed to fetch http://http.kali.org/kali/dists/kali-rolling/InRelease The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org>
W: Some index files failed to download. They have been ignored, or old ones used instead.
root@kali:~#

Can someone help me fix this?