Ubuntu – getting authentication errors for packages from an Ubuntu repository

aptauthenticationpackage-management

I'm experimenting with VPNs, so I wanted to install pptpd.

john@desktop:~$ sudo apt-get install pptpd
[sudo] password for john: 
<snip>
The following extra packages will be installed:
  bcrelay
The following NEW packages will be installed:
  bcrelay pptpd
0 upgraded, 2 newly installed, 0 to remove and 11 not upgraded.
Need to get 90.5 kB of archives.
After this operation, 442 kB of additional disk space will be used.
Do you want to continue [Y/n]? y

And everything runs fine until I get down to here:

WARNING: The following packages cannot be authenticated!
  bcrelay pptpd
Install these packages without verification [y/N]? n
E: Some packages could not be authenticated

No authentication? I'm no security expert, but I'm fairly sure that's a bad thing. So I check to see where the packages are coming from.

john@desktop:~$ apt-cache policy pptpd
pptpd:
  Installed: (none)
  Candidate: 1.3.4-3ubuntu1
  Version table:
     1.3.4-3ubuntu1 0
        500 http://us.archive.ubuntu.com/ubuntu/ natty/main i386 Packages
john@desktop:~$ apt-cache policy bcrelay
bcrelay:
  Installed: (none)
  Candidate: 1.3.4-3ubuntu1
  Version table:
     1.3.4-3ubuntu1 0
        500 http://us.archive.ubuntu.com/ubuntu/ natty/main i386 Packages

They're coming from Ubuntu.com and not being properly authenticated? What's going on here?

Best Answer

apt-key utility

apt-key is used to manage the list of keys used by apt to verify packages. Packages which have been verified using these keys will be considered trusted. To update the local keyring with the keyring of Ubuntu archive keys and removes from the keyring the archive keys which are no longer valid.

$ sudo apt-key update
$ sudo apt-get update

try install something...

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