134 research outputs found
Simple Distributed Weighted Matchings
Wattenhofer [WW04] derive a complicated distributed algorithm to compute a
weighted matching of an arbitrary weighted graph, that is at most a factor 5
away from the maximum weighted matching of that graph. We show that a variant
of the obvious sequential greedy algorithm [Pre99], that computes a weighted
matching at most a factor 2 away from the maximum, is easily distributed. This
yields the best known distributed approximation algorithm for this problem so
far
Self-stabilizing mutual exclusion on a ring, even if K=N
We show that, contrary to common belief, Dijkstra's self-stabilizing mutual
exclusion algorithm on a ring [Dij74,Dij82] also stabilizes when the number of
states per node is one less than the number of nodes on the ring.Comment: 2 page
Secure Method Invocation in JASON
We describe the Secure Method Invocation (SMI) framework implemented for Jason, our Javacard As Secure Objects Networks platform. Jason realises the secure object store paradigm, that reconciles the card-as-storage-element and card-as-processing-element views. In this paradigm, smart cards are viewed as secure containers for objects, whose methods can be called straightforwardly and securely using SMI. Jason is currently being developed as a middleware layer that securely interconnects an arbitrary number of smart cards, terminals and back-office systems over the Internet
Long-lives Test-And-Set Using
This paper studies the problem of implementing a shared memory test-and-set object using only shared registers. Our contribution is threefold. First, we present a general framework to allow reasoning about reusing one-shot shared memory objects in the construction of bounded space long-lived objects. Then we derive general theorems about test-and set objects that simplifies reasoning about their implementation. Finally we show the validity of our approach by constructing an n process long lived test-and-set object from n + 1 one-shot test-and-set objects, and proving this construction formally correct
Private Handshakes
Private handshaking allows pairs of users to determine which (secret) groups
they are both a member of. Group membership is kept secret to everybody else.
Private handshaking is a more private form of secret handshaking, because it
does not allow the group administrator to trace users. We extend the original
definition of a handshaking protocol to allow and test for membership of
multiple groups simultaneously. We present simple and efficient protocols for
both the single group and multiple group membership case.
Private handshaking is a useful tool for mutual authentication, demanded by
many pervasive applications (including RFID) for privacy. Our implementations
are efficient enough to support such usually resource constrained scenarios
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