gpgsm software package provides GNU privacy guard - S/MIME version, you can install in your Ubuntu 17.04 (Zesty Zapus) 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 17 04 zesty zapus |
| Section | Utilities |
| Package | gpgsm |
| Version | 2.1.15-1ubuntu6 |
| Description | GNU privacy guard - S/MIME version |
| Sub Section | utils |