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) <ftpmaster@debian.org>" not changed
gpg: key 6070D3A1: "Debian Archive Automatic Signing Key (4.0/etch) <ftpmaster@debian.org>" not chan ged
gpg: key ADB11277: "Etch Stable Release Key <debian-release@lists.debian.org>" 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