gnupg1-curl software package provides GNU privacy guard - a free PGP replacement (cURL helpers for classic version), 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 gnupg1-curl
gnupg1-curl is installed in your system.
Make ensure the gnupg1-curl package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnupg1-curl *
You will get with gnupg1-curl package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Utilities |
| Package | gnupg1-curl |
| Version | 1.4.21-1+b1 |
| Description | GNU privacy guard - a free PGP replacement (cURL helpers for classic version) |
| Sub Section | Utils |