ecryptfs-utils software package provides ecryptfs cryptographic filesystem (utilities), you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install ecryptfs-utils
ecryptfs-utils is installed in your system.
Make ensure the ecryptfs-utils package were installed using the commands given below,
$ sudo dpkg-query -l | grep ecryptfs-utils *
You will get with ecryptfs-utils package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Miscellaneous |
| Package | ecryptfs-utils |
| Version | 111-2 |
| Description | ecryptfs cryptographic filesystem (utilities) |
| Sub Section | Miscellaneous |