Securely sharing and managing personal content is a challenging task in multi-device environments. In this paper, we design and implement a new platform called personal content networking (PCN). Our work is inspired by content-centric networking (CCN) because we aim to enable access to personal content using its name instead of its location. The unique challenge of PCN is to support secure file operations such as replication, updates, and access control over distributed untrusted devices. The primary contribution of this work is the design and implementation of a secure content management platform that supports secure updates, replications, and fine-grained content-centric access control of files. Furthermore, we demonstrate its feasibility through a prototype implementation on the CCNx skeleton.
: The following concepts are closely related: user authentication, access control authorization, and data confidentiality. Existing access control systems can be classified based on their authentication method. When AUTH (UNIX's default) and Kerberos are used, systems mostly provide UNIX-style ACL (e.g. Network File System (NFS), Andrew File System (AFS), xFS @cite_26 ). When public key cryptography is used, systems typically support either UNIX-style ACL (e.g. SFS @cite_38 ) or certificate authorization (e.g. DisCFS @cite_27 ). These systems assume that , but the network is not secure; thus, data confidentiality is guaranteed through securing the channel (e.g. SSL). If the servers are not trustworthy, we can either rely on other semi-trusted servers as in Cobalt @cite_47 or use cryptographic encryption to preserve data confidentiality as in Cryptographic File System (CFS) @cite_32 , Plutus @cite_1 , and SiRiUS @cite_46 . A detailed survey of recent decentralized access control has been presented in this survey paper @cite_10 .
@cite_38 @cite_26 @cite_46 @cite_1 @cite_32 @cite_27 @cite_47 @cite_10
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No secure network file system has ever grown to span the Internet. Existing systems all lack adequate key management for security at a global scale. Given the diversity of the Internet, any particular mechanism a file system employs to manage keys will fail to support many types of use.We propose separating key management from file system security, letting the world share a single global file system no matter how individuals manage keys. We present SFS, a secure file system that avoids internal key management. While other file systems need key management to map file names to encryption keys, SFS file names effectively contain public keys, making them self-certifying pathnames. Key management in SFS occurs outside of the file system, in whatever procedure users choose to generate file names.Self-certifying pathnames free SFS clients from any notion of administrative realm, making inter-realm file sharing trivial. They let users authenticate servers through a number of different techniques. The file namespace doubles as a key certification namespace, so that people can realize many key management schemes using only standard file utilities. Finally, with self-certifying pathnames, people can bootstrap one key management mechanism using another. These properties make SFS more versatile than any file system with built-in key management. This paper presents SiRiUS, a secure file system designed to be layered over insecure network and P2P file systems such as NFS, CIFS, OceanStore, and Yahoo! Briefcase. SiRiUS assumes the network storage is untrusted and provides its own read-write cryptographic access control for file level sharing. Key management and revocation is simple with minimal out-of-band communication. File system freshness guarantees are supported by SiRiUS using hash tree constructions. SiRiUS contains a novel method of performing file random access in a cryptographic file system without the use of a block server. Extensions to SiRiUS include large scale group sharing using the NNL key revocation construction. Our implementation of SiRiUS performs well relative to the underlying file system despite using cryptographic operations. Plutus is a cryptographic storage system that enables secure file sharing without placing much trust on the file servers. In particular, it makes novel use of cryptographic primitives to protect and share files. Plutus features highly scalable key management while allowing individual users to retain direct control over who gets access to their files. We explain the mechanisms in Plutus to reduce the number of cryptographic keys exchanged between users by using filegroups, distinguish file read and write access, handle user revocation efficiently, and allow an untrusted server to authorize file writes. We have built a prototype of Plutus on OpenAFS. Measurements of this prototype show that Plutus achieves strong security with overhead comparable to systems that encrypt all network traffic. Although cryptographic techniques are playing an increasingly important role in modern computing system security, user-level tools for encrypting file data are cumbersome and suffer from a number of inherent vulnerabilities. The Cryptographic File System (CFS) pushes encryption services into the file system itself. CFS supports secure storage at the system level through a standard Unix file system interface to encrypted files. Users associate a cryptographic key with the directories they wish to protect. Files in these directories (as well as their pathname components) are transparently encrypted and decrypted with the specified key without further user intervention; cleartext is never stored on a disk or sent to a remote file server. CFS can use any available file system for its underlying storage without modification, including remote file servers such as NFS. System management functions, such as file backup, work in a normal manner and without knowledge of the key. This paper describes the design and implementation of CFS under Unix. Encryption techniques for file system-level encryption are described, and general issues of cryptographic system interfaces to support routine secure computing are discussed. Trust management credentials directly authorize actions, rather than divide the authorization task into authentication and access control. Unlike traditional credentials, which bind keys to principals, trust management credentials bind keys to the authorization to perform certain tasks. The Distributed Credential FileSystem (DisCFS) uses trust management credentials to identify: (1) files being stored; (2) users; and (3) conditions under which their file access is allowed. Users share files by delegating access rights, issuing credentials in the style of traditional capabilities. Credentials permit, for example, access by remote users not known in advance to the file server, which simply enforces sharing policies rather than entangling itself in their management. Throughput and latency benchmarks of our prototype DisCFS implementation indicate performance roughly comparable to NFS version 2, while preserving the advantages of credentials for distributed control. How should a distributed file system manage access to protected content? On one hand, distributed storage should make data access pervasive: authorized users should be able to access their data from any location. On the other hand, content protection is designed to restrict access -- this is often accomplished by limiting the set of computers from which content can be accessed. In this paper, we propose a new method for storing content in distributed storage called Cobalt. Rather than grant access to data based on the computer that reads the data, Cobalt grants access based on the physical proximity of authorized users. Protected content is stored encrypted in the distributed Blue File System; files can only be decrypted through the cooperation of a personal, mobile device such as cell phone. The Cobalt device is verified by content providers: it acts as a proxy that protects their interests by only decrypting data when policies specified during content acquisition are satisfied. Wireless communication with the device is used to determine the physical proximity of its user; when the Cobalt device moves out of range, protected content is made inaccessible. Our results show that Cobalt adds only modest overhead to content acquisition and playback, yet it enables new forms of interaction such as the ability to access protected content on ad hoc media players and create playlists that adapt to the tastes of nearby users. The Internet enables global sharing of data across organizational boundaries. Distributed file systems facilitate data sharing in the form of remote file access. However, traditional access control mechanisms used in distributed file systems are intended for machines under common administrative control, and rely on maintaining a centralized database of user identities. They fail to scale to a large user base distributed across multiple organizations. We provide a survey of decentralized access control mechanisms in distributed file systems intended for large scale, in both administrative domains and users. We identify essential properties of such access control mechanisms. We analyze both popular production and experimental distributed file systems in the context of our survey.