alucard@kenobi:~$ sudo apt-get install --reinstall debian-archive-keyring Reading package lists... Done Building dependency tree... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded. Need to get 0B/7880B of archives. After unpacking 0B of additional disk space will be used. Do you want to continue [Y/n]? y WARNING: The following packages cannot be authenticated! debian-archive-keyring Install these packages without verification [y/N]? y (Reading database ... 46864 files and directories currently installed.) Preparing to replace debian-archive-keyring 2007.02.19 (using .../debian-archive-keyring_2007.02.19_ all.deb) ... Unpacking replacement debian-archive-keyring ... Setting up debian-archive-keyring (2007.02.19) ... gpg: key 2D230C5F: "Debian Archive Automatic Signing Key (2006) " not changed gpg: key 6070D3A1: "Debian Archive Automatic Signing Key (4.0/etch) " not chan ged gpg: key ADB11277: "Etch Stable Release Key " not changed gpg: Total number processed: 3 gpg: unchanged: 3 alucard@kenobi:~$ sudo apt-get install -t testing debian-archive-keyring Reading package lists... Done Building dependency tree... Done debian-archive-keyring is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 89 not upgraded. alucard@kenobi:~$ sudo apt-get install -t testing postfix Reading package lists... Done Building dependency tree... Done [...] WARNING: The following packages cannot be authenticated! postfix Install these packages without verification [y/N] n