idn software package provides 1.29-1+deb8u2, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install idn
idn is installed in your system.
Make ensure the idn package were installed using the commands given below,
$ sudo dpkg-query -l | grep idn *
You will get with idn package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Miscellaneous |
| Package | idn |
| Version | 1.29-1+deb8u2 |
| Description | 1.29-1+deb8u2 |
| Sub Section | Misc |