Linux systems use Encrypting File System (EFS) for providing confidentiality and integrity services to files stored on disk in a secure, efficient and transparent manner. Distributed encrypting file system should also provide support for secure remote access, multiuser file sharing, possible use by non-privileged users, portability, incremental backups etc. Existing kernel-space EFS designed at file system level provides all necessary features, but they are not portable and cannot be mounted by non-privileged users. Existing user-space EFS have performance limitations and does not provide support for file sharing.
Through this paper, modifications in the design and implementation of two existing user-space EFS, for performance gain and file sharing support, has been presented. Performance gain has been achieved in both the proposed approaches using fast and modern ciphers. File sharing support in proposed approaches has been provided with Public Key Infrastructure (PKI) integration using GnuPG PKI module and Linux Pluggable Authentication Module (PAM) framework. Cryptographic metadata is being stored as extended attributes in file's Access Control List (ACL) to make file sharing task easier and seamless to the end user.