Cryptfs: A Stackable Vnode Level Encryption File System

Data encryption has become an increasingly important factor in everyday work. Users seek a method of securing their data with maximum comfort and minimum additional requirements on their part; they want a security system that protects any files used by any of their applications, without resorting to application-specific encryption methods. Performance is an important factor to users since encryption can be time consuming. Operating system vendors want to provide this functionality but without incurring the large costs of developing a new file system. This paper describes the design and implementation of Cryptfs -- a file system that was designed as a stackable Vnode layer loadable kernel module. Cryptfs operates by 'encapsulating' a client file system with a layer of encryption transparent to the user. Being kernel resident, Cryptfs performs better than user-level or NFS based file servers such as CFS and TCFS. It is 2 to 37 times faster on micro-benchmarks such as read and write; this translates to 12-52\%application speedup, as exemplified by a large build. Cryptfs offers stronger security by basing its keys on process session IDs as well as user IDs, and by the fact that kernel memory is harder to access. Working at and above the vnode level, Cryptfs is more portable than a file system which works directly with native media such as disks and networks. Cryptfs can operate on top of any other native file system such as UFS/FFS and NFS. Finally, Cryptfs requires no changes to client file systems or remote servers

Interplay of quantum and thermal fluctuations in a frustrated magnet

We demonstrate the presence of an extended critical phase in the transverse field Ising magnet on the triangular lattice, in a regime where both thermal and quantum fluctuations are important. We map out a complete phase diagram by means of quantum Monte Carlo simulations, and find that the critical phase is the result of thermal fluctuations destabilising an order established by the quantum fluctuations. It is separated by two Kosterlitz-Thouless transitions from the paramagnet on one hand and the quantum-fluctuation driven three-sublattice ordered phase on the other. Our work provides further evidence that the zero temperature quantum phase transition is in the 3d XY universality class.Comment: 9 pages, revtex

Extending File Systems Using Stackable Templates

Extending file system functionality is not a new idea, but a desirable one nonetheless[6, 14, 18]. In the several years since stackable file systems were first proposed, only a handful are in use[12, 19]. Impediments to writing new file systems include the complexity of operating systems, the difficulty of writing kernel-based code, the lack of a true stackable vnode interface[14], and the challenges of porting one file system to another operating system. We advocate writing new stackable file systems as kernel modules. As a starting point, we propose a portable, stackable template file system we call Wrapfs (wrapper file system). Wrapfs is a canonical, minimal stackable file system that can be used as a pattern across a wide range of operating systems and file systems. Given Wrapfs, developers can add or modify only that which is necessary to achieve the desired functionality. Wrapfs takes care of the rest, and frees developers from the details of operating systems. Wrapfs templates ..