Abstract: A backup device for a computer network is able to back up all shared files without the need to install software on the computers. A backup device, including a DVD drive, is connected to the network and includes all of the necessary software for execution. The backup device retrieves the files and directories for all computers on the network. A user can then designate the folders and files to be backed up. Folders are designated using different states which clarify the backup states of new subfolders and files. Backup files are stored based upon a digest of the file contents. The digest allows identical files, anywhere in the network, to be backed up only once. The folder system of the backup device uses the digests to determine storage locations for quick storage and retrieval. Encryption and key control are handled by the backup device in order to protect the backed up data.