On the sensitivity of the HAWC observatory to gamma-ray bursts

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles

TATA: Towards Anonymous Trusted Authentication

Mobile devices may share resources even in the presence of untrustworthy devices. To do so, each device may use a computational model that on input of reputation information produces trust assessments. Based on such assessments, the device then decides with whom to share: it will likely end up sharing only with the most trustworthy devices, thus isolating the untrustworthy ones. All of this is, however, theoretical in the absence of a general and distributed authentication mechanism. Currently, distributed trust frameworks do not offer an authentication mechanism that supports user privacy, whilst being resistant to “Sybil attacks”. To fill the gap, we first analyze the general attack space that relates to anonymous authentication as it applies to distributed trust models. We then put forward a scheme that is based on blinded threshold signature: collections of devices certify pseudonyms without seeing them and without relying on a central authority. We finally discuss how the scheme tackles the authentication attacks

How to Share Your Favourite Search Results while Preserving Privacy and Quality

Personalised social search is a promising avenue to increase the relevance of search engine results by making use of recommendations made by friends in a social network. More generally a whole class of systems take user preferences, aggregate and process them, before providing a view of the result to others in a social network. Yet, those systems present privacy risks, and could be used by spammers to propagate their malicious preferences. We present a general framework to preserve privacy while maximizing the benefit of sharing information in a social network, as well as a concrete proposal making use of cohesive social group concepts from social network analysis. We show that privacy can be guaranteed in a k-anonymity manner, and disruption through spam is kept to a minimum in a real world social network. © 2010 Springer-Verlag Berlin Heidelberg