Seeing the following error on running sudo apt-get update
W: GPG error: http://security.debian.org jessie/updates InRelease: The following signatures were invalid: KEYEXPIRED 1668892417 The following signatures couldn't be verified because the public key is not available: NO_PUBKEY AA8E81B4331F7F50
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie-updates/main/binary-amd64/Packages 404 Not Found