network measurements
Recently Published Documents


TOTAL DOCUMENTS

177
(FIVE YEARS 26)

H-INDEX

22
(FIVE YEARS 2)

2021 ◽  
Vol 2022 (1) ◽  
pp. 522-543
Author(s):  
Lennart Oldenburg ◽  
Gunes Acar ◽  
Claudia Diaz

Abstract We present a novel web-based attack that identifies a Tor user’s guard in a matter of seconds. Our attack is low-cost, fast, and stealthy. It requires only a moderate amount of resources and can be deployed by website owners, third-party script providers, and malicious exits—if the website traffic is unencrypted. The attack works by injecting resources from non-existing onion service addresses into a webpage. Upon visiting the attack webpage with Tor Browser, the victim’s Tor client creates many circuits to look up the non-existing addresses. This allows middle relays controlled by the adversary to detect the distinctive traffic pattern of the “404 Not Found” lookups and identify the victim’s guard. We evaluate our attack with extensive simulations and live Tor network measurements, taking a range of victim machine, network, and geolocation configurations into account. We find that an adversary running a small number of HSDirs and providing 5 % of Tor’s relay bandwidth needs 12.06 seconds to identify the guards of 50 % of the victims, while it takes 22.01 seconds to discover 90 % of the victims’ guards. Finally, we evaluate a set of countermeasures against our attack including a defense that we develop based on a token bucket and the recently proposed Vanguards-lite defense in Tor.


Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7479
Author(s):  
Jesús Velázquez ◽  
Javier Conte ◽  
Ana Cristina Majarena ◽  
Jorge Santolaria

Laser trackers (LT) are widely used to calibrate other machines. Nevertheless, very little is known about calibrating an LT. There are some standards that allow us to evaluate the LT performance. However, they require specialized equipment. A calibration procedure to improve the LT accuracy in an easy and fast way is presented in this paper. This method is based on network measurements where a set of reflectors were measured from different LT positions in a working environment. The methodology proposed deal with the lack of nominal data of the reflector mesh. A measurement scenario was defined, based on error parameter dependence on distances and angles, thus, obtaining those positions more sensitive to errors. The influence of the incidence angle of the laser beam on the reflector was characterized, revealing that its contribution to the LT measurement error can be up to 13 µm. Error kinematic parameters were identified to provide the optimum value of an objective function, where the reflector mesh nominal data were unknown. The calibration procedure was validated with nominal data, by measuring a set of reflectors located on a coordinate measuring machine. The findings of this study suggested that the LT accuracy can be improved up to 25%. Moreover, the method can be carried out by the LT user without requiring specialized equipment.


2021 ◽  
Author(s):  
Petya Vasileva ◽  
Shawn McKee ◽  
Alexander Penev ◽  
Ilija Vukotic
Keyword(s):  

Network ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 215-232
Author(s):  
Florian Wamser ◽  
Anika Seufert ◽  
Andrew Hall ◽  
Stefan Wunderer ◽  
Tobias Hoßfeld

Crowdsourced network measurements (CNMs) are becoming increasingly popular as they assess the performance of a mobile network from the end user’s perspective on a large scale. Here, network measurements are performed directly on the end-users’ devices, thus taking advantage of the real-world conditions end-users encounter. However, this type of uncontrolled measurement raises questions about its validity and reliability. The problem lies in the nature of this type of data collection. In CNMs, mobile network subscribers are involved to a large extent in the measurement process, and collect data themselves for the operator. The collection of data on user devices in arbitrary locations and at uncontrolled times requires means to ensure validity and reliability. To address this issue, our paper defines concepts and guidelines for analyzing the precision of CNMs; specifically, the number of measurements required to make valid statements. In addition to the formal definition of the aspect, we illustrate the problem and use an extensive sample data set to show possible assessment approaches. This data set consists of more than 20.4 million crowdsourced mobile measurements from across France, measured by a commercial data provider.


2021 ◽  
Author(s):  
Mathew Vermeer ◽  
Jonathan West ◽  
Alejandro Cuevas ◽  
Shuonan Niu ◽  
Nicolas Christin ◽  
...  
Keyword(s):  

Sign in / Sign up

Export Citation Format

Share Document