erlang-crypto software package provides Erlang/OTP cryptographic modules, 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 erlang-crypto
erlang-crypto is installed in your system.
Make ensure the erlang-crypto package were installed using the commands given below,
$ sudo dpkg-query -l | grep erlang-crypto *
You will get with erlang-crypto package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Interpreters |
| Package | erlang-crypto |
| Version | 1:19.1.5+dfsg-1 |
| Description | Erlang/OTP cryptographic modules |
| Sub Section | Interpreters |