This paper describes a novel shared file system, whose main features are enhanced security and its concurrency control mechanism. The system is especially suitable for access from mobile hosts. Users can edit their shared files concurrently. Shared files are encrypted and decrypted only by clients, and the file server cannot know the contents. The server asynchronously receives the edited parts, which are already encrypted, and merges them into the current version, deciphering neither the stored file nor the encrypted editing data. We call the mechanism 'privacy enhanced merging'. The mechanism and the underlying encryption algorithm, shared file data structure and procedures followed by clients and the server are shown.