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Social network sites (SNS) allow users to share information with friends, family, and other contacts. However, current SNS sites such as Facebook or Twitter assume that users trust SNS providers with the access control of their data. In this paper we propose Scramble, the implementation of a SNS-independent Firefox extension that allows users to enforce access control over their data. Scramble lets users define access control lists (ACL) of authorised users for each piece of data, based on their preferences. The definition of ACL is facilitated through the possibility of dynamically defining contact groups. In turn, the confidentiality and integrity of one data item is enforced using cryptographic techniques. When accessing a SNS that contains data encrypted using Scramble, the plugin transparently decrypts and checks integrity of the encrypted content.

In 2008, Wan et al. presented an anonymous ID-based group key agreement scheme for wireless networks, for which they claim that it ensures anonymity and unlinkability of the group members, as well as forward and backward secrecy of the group session key. In this paper, we show that forward and backward secrecy do not hold for the protocol. We propose a correction that introduces a shielding factor that protects each member's input to the group key. we also introduce a new feature that assures the correctness of the key as computed by all group members. This results in an increased computation cost, due to extra public key operations, and a similar communication cost. We also show in which practical setting the protocol can be deployed. © 2011 Springer-Verlag Berlin Heidelberg. ispartof: pages:214-222 ispartof: Lecture Notes in Computer Science vol:6543 pages:214-222 ispartof: SOFSEM 2011 location:SLOVAKIA, Novy Smokovec date:22 Jan - 28 Jan 2011 status: published