[R-sig-Debian] Problems with public key

[hugo]

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?