Error authenticating some packages while upgrade

When I try to upgrade my ubuntu 13.04 to 13.10, it gives the following error:

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.

Also while downloading the files, I see such errors like:

Err http://in.archive.ubuntu.com saucy-backports/restricted Translation-en_IN 

I tried the link to a similar question but that does not work. I don't think I have any troubles with the keys.

Solution 1:

Important Security Notice

This answer will disable an critical security feature in Ubuntu. It will stop Ubuntu checking packages are the the same as they were when they were built.

This could mean your updates are compromised or corrupt.
This could mean there's just a bug in the way Ubuntu's release upgrades are handled.

I'm not saying you should never do this, I'm just asking you to be aware of what you're doing. And put things back after you upgrade. Don't leave AllowUnauthenticated on indefinitely.

— Oli, Ask Ubuntu mod.

This worked out for me.

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.