61 research outputs found
A First-Hop Traffic Analysis Attack Against Tor
We introduce an attack against encrypted web
traffic passing over the first hop – between client and Tor gateway
– of the Tor network. The attack makes use only of packet timing
information on the uplink and so is impervious to packet padding
defences. In addition, we show that the attack is robust against the
randomised routing used in Tor. We demonstrate the effectiveness
of the attack at identifying the web sites being visited by a Tor
user, achieving mean success rates of 68%. As well as being of
interest in its own right, this timing-only attack serves to highlight
deficiencies in existing defences and so to areas where it would be
beneficial for Tor and VPN designers to focus further attention
An Efficient Anonymous Authentication Scheme Using Registration List in VANETs
Nowadays, Vehicular Ad hoc Networks (VANETs) are popularly known as they can
reduce traffic and road accidents. These networks need several security
requirements, such as anonymity, data authentication, confidentiality,
traceability and cancellation of offending users, unlinkability, integrity,
undeniability and access control. Authentication is one of the most important
security requirements in these networks. So many authentication schemes have
been proposed up to now. One of the well-known techniques to provide users
authentication in these networks is the authentication based on the smartcard
(ASC). In this paper, we propose an ASC scheme that not only provides necessary
security requirements such as anonymity, traceability and unlinkability in the
VANETs but also is more efficient than the other schemes in the literatures.Comment: 5 pages, 4 figures, Accepted for ICEE202
A Low Complexity Space-Time Block Codes Detection for Cell-Free Massive MIMO Systems
The new generation of telecommunication systems must provide acceptable data
rates and spectral efficiency for new applications. Recently massive MIMO has
been introduced as a key technique for the new generation of telecommunication
systems. Cell-free massive MIMO system is not segmented into cells. Each BS
antennas are distributed throughout the environment and each user is served by
all BSs, simultaneously.
In this paper, the performance of the multiuser cell-free massive MIMO-system
exploying space-time block codes in the uplink, and with linear decoders is
studied. An Inverse matrix approximation using Neumann series is proposed to
reduce the computational and hardware complexity of the decoding in the
receiver.
For this purpose, each user has two antennas, and also for improving the
diversity gain performance, space-time block codes are used in the uplink.
Then, Neumann series is used to approximate the inverse matrix in ZF and MMSE
decoders, and its performance is evaluated in terms of BER and spectral
efficiency.
In addition, we derive lower bound for throughput of ZF decoder.
The simulation results show that performance of the system , in terms of BER
and spectral efficiency, is better than the single-antenna users at the same
system. Also, the BER performance in a given system with the proposed method
will be close to the exact method.Comment: 5 pages, 4 figures, Accepted for ICEE202
Impact of two parasitic trematodes, Meiogymnophallus minutus and Himasthla spp., on the growth of the cockle, Cerastoderma edule
The impact of two principal parasitic digenetic trematodes, Meiogymnophallus minutus and Himasthla spp., on the growth (weight and length) of the cockle, Cerastoderma edule, in Arcachon Bay (France) was studied. The experiment was conducted in the land-based mesocosms. The velocity of infestation with both trematodes was far more rapid during summer in the cockles already parasitized with these trematodes (0.35 to 0.45 metacercariae day-1) than those of healthy ones (approximately 0.01 metacercariae day-1). The parasitism had also an effect on the growth rates of cockles. During 190 days of the experiment, the daily growth speed varied from 0.001mm.da/ to 0.021mm.day-1. On average, the growth was slightly more important in healthy cockles after the start of experiments (0.014mm.day-1) than those initially infested cockles (0.011 mm.day-1). The experiment also showed that infestation of hosts with trematodes could perhaps disturb their immunity system, as the intensification with trematode parasites had been favored by already infested cockles
Platelet clearance via shear-induced unfolding of a membrane mechanoreceptor
Mechanisms by which blood cells sense shear stress are poorly characterized. In platelets, glycoprotein (GP)Ib-IX receptor complex has been long suggested to be a shear sensor and receptor. Recently, a relatively unstable and mechanosensitive domain in the GPIba subunit of GPIb-IX was identified. Here we show that binding of its ligand, von Willebrand factor, under physiological shear stress induces unfolding of this mechanosensory domain (MSD) on the platelet surface. The unfolded MSD, particularly the juxtamembrane € Trigger' sequence therein, leads to intracellular signalling and rapid platelet clearance. These results illustrate the initial molecular event underlying platelet shear sensing and provide a mechanism linking GPIb-IX to platelet clearance. Our results have implications on the mechanism of platelet activation, and on the pathophysiology of von Willebrand disease and related thrombocytopenic disorders. The mechanosensation via receptor unfolding may be applicable for many other cell adhesion receptors
Mechanobiology of Platelets: Techniques to Study the Role of Fluid Flow and Platelet Retraction Forces at the Micro- and Nano-Scale
Coagulation involves a complex set of events that are important in maintaining hemostasis. Biochemical interactions are classically known to regulate the hemostatic process, but recent evidence has revealed that mechanical interactions between platelets and their surroundings can also play a substantial role. Investigations into platelet mechanobiology have been challenging however, due to the small dimensions of platelets and their glycoprotein receptors. Platelet researchers have recently turned to microfabricated devices to control these physical, nanometer-scale interactions with a higher degree of precision. These approaches have enabled exciting, new insights into the molecular and biomechanical factors that affect platelets in clot formation. In this review, we highlight the new tools used to understand platelet mechanobiology and the roles of adhesion, shear flow, and retraction forces in clot formation
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