Error authenticating some packages

i can proceede with following steps:

--------------------
create the file /etc/update-manager/release-upgrades.d/unauth.cfg as root and add the following.

[Distro]
AllowUnauthenticated=yes
After upgrade, remove this file.
--------------------

but, still interesting why package libgbm1 have authenticating error. here is policy:

-------------------
$ apt-cache policy libgbm1
libgbm1:
  Installed: 10.1.3-0ubuntu0.1
  Candidate: 10.1.3-0ubuntu0.1
  Version table:
 *** 10.1.3-0ubuntu0.1 0
        500 http://archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     10.1.0-4ubuntu5 0
        500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
-------------------

I have the same error with a different package:

Error authenticating some packages

It was not possible to authenticate some packages. This may be a
transient network problem. You may want to try again later. See below
for a list of unauthenticated packages.

libertas-firmware

Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done

Did you or anyone reading figure out why this is happening?

Thank you for sharing your post on this.

Here is the policy for my post #3:

libertas-firmware:
  Installed: 9.70.7.p0.0-1
  Candidate: 9.70.7.p0.0-2
  Version table:
     9.70.7.p0.0-2 0
        500 http://archive.ubuntu.com/ubuntu/ trusty/multiverse i386 Packages
 *** 9.70.7.p0.0-1 0
        100 /var/lib/dpkg/status

Status changed to 'Confirmed' because the bug affects multiple users.

Still getting this when going 14.04->16.04. It complained about my kernel image package. I upgraded to the latest kernel, removed all older kernel packages, now it complained about my fresh installed kernel package.

What does this even mean? What is it authenticating?

Trying the disabling config from the comments above.