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In this paper we consider the mutual exclusion problem on a multiple access channel. Mutual exclusion is one of the fundamental problems in distributed computing. In the classic version of this problem, n processes perform a concurrent program which occasionally triggers some of them to use shared resources, such as memory, communication channel, device,(More)
We analyze networks of mixes used for providing untraceable communication. We consider a network consisting of k mixes working in parallel and exchanging the outputs – which is the most natural architecture for composing mixes of a certain size into networks able to mix a larger number of inputs at once. We prove that after O(log k) rounds the network(More)
Recently, David Chaum proposed an electronic voting scheme that combines visual cryptography and digital processing. It was designed to meet not only mathematical security standards, but also to be accepted by voters that do not trust electronic devices. In this scheme mix-servers are used to guarantee anonymity of the votes in the counting process. The(More)
Anonymous communication protocols, very essential for preserving privacy of the parties communicating, may lead to severe problems. A malicious server may use anonymous communication protocols for injecting unwelcome messages into the system so that their source can be hardly traced. So anonymity and privacy protection on one side and protection against(More)
Encapsulating messages in onions is one of the major techniques providing anonymous communication in computer networks. To some extent, it provides security against traffic analysis by a passive adversary. However, it can be highly vulnerable to attacks by an active adversary. For instance, the adversary may perform a simple so–called repetitive attack: a(More)
We consider unlinkability of communication problem: given n users, each sending a message to some destination, encode and route the messages so that an adversary analyzing the traffic in the communication network cannot link the senders with the recipients. A solution should have a small communication overhead, that is, the number of additional messages(More)
We consider a key distribution scheme for securing node-to-node communication in sensor networks. While most schemes in use are based on random predistribution, we consider a system of dynamic pairwise keys based on design due to Ren, Tanmoy and Zhou. We design and analyze a variation of this scheme, in which capturing a node does not lead to security(More)