ID replaced by md5 code or something stronger

Hy,

I installed this plugin to provide download links for files shared by e-mail, the most simply possible.

Unfortunately, I Have this results :

http://www.example.com/downloads/4367
http://www.example.com/downloads/4368
http://www.example.com/downloads/4369

I don’t want my customers to be able to download an other link just by changing the ID.

Is it possible to have :

http://www.example.com/downloads/Diug75hf46j
http://www.example.com/downloads/KJAeRhhf46d
http://www.example.com/downloads/46uUe633IG9
etc.

I didn’t find it in free version, maybe extension ?

https://wordpress.org/plugins/download-monitor/