Thanks for your reply, I understand the part about disk drive and PBS both are not working on the same layer.Encryption on storage and encryption in PBS are completely different things. For example on storage Level ( like zfs) you need support by the storage ( zfs encryption or linux dm-crypt) while encrypted backups to PBS don't need a specific filesystem to work.
See also: https://forum.proxmox.com/threads/proxmox-deduplication.140304/post-799715
The key for PBS backups is on the ProxmoxVE Server, you will need to save it somewhere else to be able to restore your backups. For that reason it's a good idea to backup everything in /etc/pve outside of PBS.
I enabled encryption on PVE for PBS Backups yesterday but I still don't know on which layer the encryption is done and with which protocol. For now my last backup is encrypted (cf: pic) but only the diff is encrypted (only half of the previous backup has been reused). The fact that I don't want my file to be unencrypted.
