Hello @Jade_SAS, a pleasure.
This is what I meant: https://en.wikipedia.org/wiki/List_of_cryptographic_file_systems then you can create a shared folder or a mount on the top of it.
Anyway, just using your current shared or clustered file system on your Grid (a new one, to not fill in the current one whis is supposed to be for your SAS configuration only) should be enough. Then the last step for you would be to create some shared folders where only the people you want can access.
Also, as said, SFTP is another good option. SFTP is just the secured version of FTP.