I had the same problem. I changed the ubuntu software server from "Download from: Server for India" to "Download from:Main Server" updates and software downloads ---> works for me!
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/705988 Title: [master] Untrusted packages can not be installed -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
