All Celtx studio connections are encrypted using HTTPS. Content is encrypted in transit between the server and your computer.
As well, your projects and files are maintained within Amazon's proven network infrastructure and data-centers. Backups are replicated to multiple geographic locations to prevent data loss.
Sharing
Files are also private unless you explicitly share them with someone, or are a member of a team account. When you do choose to share files, you can specify if you want someone to have Reader or Writer editing privileges.