Apt-Get Update security failure

Question

I'm running a 3B+ with Raspbian Stretch 11/18 update. sudo apt-get update is returning this:

W: GPG error: http://deb.debian.org/debian stretch-updates InRelease: The following signatures couldn't be verified beca     use the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010
W: The repository 'http://deb.debian.org/debian stretch-updates InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://deb.debian.org/debian stretch Release: The following signatures couldn't be verified because the pu     blic key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY EF0F382A1A7B6500
W: The repository 'http://deb.debian.org/debian stretch Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://deb.debian.org/debian/dists/stretch/main/i18n/Translation-en  BZ2_bzread: /var/lib/apt/lists/p     artial/deb.debian.org_debian_dists_stretch_main_i18n_Translation-en.bz2 Read error (-5: DATA_ERROR_MAGIC)
E: Some index files failed to download. They have been ignored, or old ones used instead.

That's only a sample; every package errors. /etc/apt/sources.list.d/* and /etc/apt/sources.list are default. I have not had problems with sudo apt-get update before today.

Any suggestions for how to fix this?

Answer 1

Your question states that your sources.list file is "default". If that's the case, I'm not sure why your errors are pointing to debian servers. You didn't show us what your /etc/apt/sources.list file looks like, but here's mine FWIW:

deb http://raspbian.raspberrypi.org/raspbian/ stretch main contrib non-free rpi