I am using Ubuntu Trusty: Linux hugo-P35-DS3L 3.13.0-68-lowlatency #111-Ubuntu SMP PREEMPT Fri Nov 6 19:08:04 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch:security-4.0-amd64:security-4.0-noarch:security-4.1-amd64:security-4.1-noarch Distributor ID: Ubuntu Description: Ubuntu 14.04.3 LTS Release: 14.04 Codename: trusty When I run the command: sudo apt-get update. I receive the error message: KEY EXPIRED 1445181253 How can correct this problem?