WARNING: The following packages cannot be authenticated! dctrl-tools

["upiter77@lycos.com" <upiter77@lycos.com>]

hi

I would like to create usb wheezy live and get this problem:

[2013-03-28 01:06:31] lb chroot_preseed 
P: Begin executing local preseeds...
[2013-03-28 01:06:31] lb chroot_package-lists install
P: Begin queueing installation of package lists (install pass)...
Reading package lists... Done
Building dependency tree... Done
Suggested packages:
  debtags
The following NEW packages will be installed:
  dctrl-tools
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 161 kB of archives.
After this operation, 554 kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
  dctrl-tools
E: There are problems and -y was used without --force-yes
P: Begin unmounting filesystems...
P: Saving caches...
Reading package lists... Done
Building dependency tree... Done

Howto solve this?

greetings
Piotr