Biblio

Though anonymity of ring signature schemes has been studied in many literatures for a long time, these papers showed different definitions and there is no consensus. Recently, Bender et al. proposed two new anonymity definitions of ring signature which is stronger than the traditional definition, that are called anonymity against attribution attacks/full key exposure. Also, ring signature schemes have two levels of unforgeability definitions, i.e., existential un-forgeability (eUF) and strong existential unforgeability (sUF). In this paper, we will redefine anonymity and unforgeability definitions from the standpoint of universally composable (UC) security framework. First, we will formulate new ideal functionalities of ring signature schemes for each security levels separately. Next, we will show relations between cryptographic security definitions and our UC definitions. Finally, we will give another proof of the Bender et al.'s ring signature scheme following the UC secure definition by constructing a simulator to an adversary of sUF, which can be adaptable to the case of sUF under the assumption of a standard single sUF signature scheme.

Ubiquitous or pervasive computing is a new kind of computing, where specialized elements of hardware and software will have such high level of deployment that their use will be fully integrated with the environment. Augmented reality extends reality with virtual elements but tries to place the computer in a relatively unobtrusive, assistive role. In this paper we propose, test and analyse a security and privacy architecture for a previously proposed middleware architecture for mobile and pervasive large scale augmented reality games, which is the main contribution of this paper. The results show that the security features proposed in the scope of this work do not affect the overall performance of the system.

BootJacker is a proof-of-concept attack tool which demonstrates that authentication mechanisms employed by an operating system can be bypassed by obtaining physical access and simply forcing a restart. The key insight that enables this attack is that the contents of memory on some machines are fully preserved across a warm boot. Upon a reboot, BootJacker uses this residual memory state to revive the original host operating system environment and run malicious payloads. Using BootJacker, an attacker can break into a locked user session and gain access to open encrypted disks, web browser sessions or other secure network connections. BootJacker's non-persistent design makes it possible for an attacker to leave no traces on the victim machine.