gpgsm software package provides GNU privacy guard - S/MIME version, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gpgsm
gpgsm is installed in your system.
Make ensure the gpgsm package were installed using the commands given below,
$ sudo dpkg-query -l | grep gpgsm *
You will get with gpgsm package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Utilities |
| Package | gpgsm |
| Version | 2.0.22-3ubuntu1.3 [amd64, i386 |
| Description | GNU privacy guard - S/MIME version |
| Sub Section | Utils |