Automatically checking commitment protocols in ProVerif without false attacks

Abstract. ProVerif over-approximates the attacker’s power to enable verification of processes under replication. Unfortunately, this results in ProVerif finding false attacks. This problem is particularly common in protocols whereby a participant commits to a particular value and later reveals their value. We introduce a method to reduce false attacks when analysing secrecy. First, we show how inserting phases into non-replicated processes enables a more accurate translation to Horn clauses which avoids some false attacks. Secondly, we generalise our methodology to processes under replication. Finally, we demonstrate the applicability of our technique by analysing BlueTooth Simple Pairing. Moreover, we propose a simplification of this protocol that achieves the same security goal.

First-Order Definability of Trees and Sparse Random Graphs

This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Let D(G) be the smallest quantifier depth of a first-order formula which is true for a graph G but false for any other non-isomorphic graph. This can be viewed as a measure for the descriptive complexity of G in first-order logic. We show that almost surely , where G is a random tree of order n or the giant component of a random graph with constant c<1. These results rely on computing the maximum of D(T) for a tree T of order n and maximum degree l, so we study this problem as well.Peer Reviewe

The cost-effectiveness of a mechanical compression device in out of hospital cardiac arrest

AIM: To assess the cost-effectiveness of LUCAS-2, a mechanical device for cardiopulmonary resuscitation (CPR) as compared to manual chest compressions in adults with non-traumatic, out-of-hospital cardiac arrest. METHODS: We analysed patient-level data from a large, pragmatic, multi-centre trial linked to administrative secondary care data from the Hospital Episode Statistics (HES) to measure healthcare resource use, costs and outcomes in both arms. A within-trial analysis using quality adjusted life years derived from the EQ-5D-3L was conducted at 12-month follow-up and results were extrapolated to the lifetime horizon using a decision-analytic model. RESULTS: 4471 patients were enrolled in the trial (1652 assigned to the LUCAS-2 group, 2819 assigned to the control group). At 12 months, 89 (5%) patients survived in the LUCAS-2 group and 175 (6%) survived in the manual CPR group. In the vast majority of analyses conducted, both within-trial and by extrapolation of the results over a lifetime horizon, manual CPR dominates LUCAS-2. In other words, patients in the LUCAS-2 group had poorer health outcomes (i.e. lower QALYs) and incurred higher health and social care costs. CONCLUSION: Our study demonstrates that the use of the mechanical chest compression device LUCAS-2 represents poor value for money when compared to standard manual chest compression in out-of-hospital cardiac arrest