Is it possible to configure Time Machine to encrypt network backups?
If you select Encrypt backups when setting up Time Machine, the backup data will be encrypted using the encryption password you enter. The password is stored in your keychain to allow its use by Time Machine.
The backup data cannot be decrypted by anyone else unless they have the password.
To further increase safety, you may want to consider setting up different users on the network drive and let each user use their own storage for their backup data.