Nicholas Hopper
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View article: Shear Thinning and Stress-Dependent Viscosity Activation Volumes: Combining Eyring and Carreau
Shear Thinning and Stress-Dependent Viscosity Activation Volumes: Combining Eyring and Carreau Open
The viscosity of fluids and their dependence on shear rate, known as shear thinning, plays a critical role in applications ranging from lubricants and coatings to biomedical and food-processing industries. Traditional models such as the Ca…
View article: Front Cover: Temperature‐Programmed Reflection Absorption Infrared Spectroscopy: A Methods Review (ChemCatChem 10/2024)
Front Cover: Temperature‐Programmed Reflection Absorption Infrared Spectroscopy: A Methods Review (ChemCatChem 10/2024) Open
The Front Cover illustrates a new method that has been proposed for measuring the kinetics of elementary surface reaction steps. In their Research Article, Robert Bavisotto, Quintus Owen, Nicholas Hopper, and Eddy Tysoe describe a method t…
View article: An Analysis of Shear-Dependent Mechanochemical Reaction Kinetics
An Analysis of Shear-Dependent Mechanochemical Reaction Kinetics Open
The variation in the rate of a tribochemical reaction is calculated as a function of combined normal and shear stresses using Evans-Polanyi perturbation theory. The effect of perturbations such as stresses is obtained using transition-stat…
View article: Modeling mechanochemistry: pressure dependence of Diels–Alder cycloaddition reaction kinetics
Modeling mechanochemistry: pressure dependence of Diels–Alder cycloaddition reaction kinetics Open
We analyze the effect of pressure on the Diels–Alder (D–A) dimerization reactions using Evans–Polanyi (E–P) theory, a thermodynamic analysis of the way in which a perturbation, in this case a hydrostatic pressure, modifies a reaction rate.
View article: DeTorrent: An Adversarial Padding-only Traffic Analysis Defense
DeTorrent: An Adversarial Padding-only Traffic Analysis Defense Open
While anonymity networks like Tor aim to protect the privacy of their users, they are vulnerable to traffic analysis attacks such as Website Fingerprinting (WF) and Flow Correlation (FC). Recent implementations of WF and FC attacks, such a…
View article: Committee Moderation on Encrypted Messaging Platforms
Committee Moderation on Encrypted Messaging Platforms Open
Encrypted messaging services like WhatsApp, Facebook Messenger, and Signal provide secure and deniable communication for billions across the world, but these exact properties prevent holding users accountable for sending messages that are …
View article: Poster: No safety in numbers: traffic analysis of sealed-sender groups in Signal
Poster: No safety in numbers: traffic analysis of sealed-sender groups in Signal Open
Secure messaging applications often offer privacy to users by protecting their messages from would be observers through end-to-end encryption techniques. However, the metadata of who communicates with whom cannot be concealed by encryption…
View article: DeTorrent: An Adversarial Padding-only Traffic Analysis Defense
DeTorrent: An Adversarial Padding-only Traffic Analysis Defense Open
While anonymity networks like Tor aim to protect the privacy of their users, they are vulnerable to traffic analysis attacks such as Website Fingerprinting (WF) and Flow Correlation (FC). Recent implementations of WF and FC attacks, such a…
View article: Exploring mechanochemical reactions at the nanoscale: theory <i>versus</i> experiment
Exploring mechanochemical reactions at the nanoscale: theory <i>versus</i> experiment Open
Mechanochemical reaction kinetics which are calculated using the steepest-descent pathway yield results that agree well with experiment for the normal-stress-induced decomposition of methyl thiolate on Cu(100).
View article: Padding-only defenses add delay in Tor
Padding-only defenses add delay in Tor Open
Website fingerprinting is an attack that uses size and timing characteristics of encrypted downloads to identify targeted websites. Since this can defeat the privacy goals of anonymity networks such as Tor, many algorithms to defend agains…
View article: RegulaTor: A Straightforward Website Fingerprinting Defense
RegulaTor: A Straightforward Website Fingerprinting Defense Open
Website Fingerprinting (WF) attacks are used by local passive attackers to determine the destination of encrypted internet traffic by comparing the sequences of packets sent to and received by the user to a previously recorded data set. As…
View article: Critical stresses in mechanochemical reactions
Critical stresses in mechanochemical reactions Open
The rates of mechanochemical reactions are generally found to increase exponentially with applied stress.
View article: Surface Chemistry at the Solid‐Solid Interface; Selectivity and Activity in Mechanochemical Reactions on Surfaces
Surface Chemistry at the Solid‐Solid Interface; Selectivity and Activity in Mechanochemical Reactions on Surfaces Open
This paper summarizes the concepts that underpin the way in which forces exerted on chemical systems can either accelerate their rates or induce reaction pathways that cannot be accessed thermally. This was first described in 1935 by Evans…
View article: GANDaLF: GAN for Data-Limited Fingerprinting
GANDaLF: GAN for Data-Limited Fingerprinting Open
We introduce Generative Adversarial Networks for Data-Limited Fingerprinting (GANDaLF), a new deep-learning-based technique to perform Website Fingerprinting (WF) on Tor traffic. In contrast to most earlier work on deep-learning for WF, GA…
View article: Infrared spectroscopic measurements of the structure of organic thin films; furfural on Pd(111) and Au(111) surfaces
Infrared spectroscopic measurements of the structure of organic thin films; furfural on Pd(111) and Au(111) surfaces Open
This work demonstrates the use of reflection–adsorption infrared spectroscopy for continually monitoring the structure of organic thin films as a function of thickness and temperature to complement diffraction methods.
View article: RegulaTOR: A Powerful Website Fingerprinting Defense.
RegulaTOR: A Powerful Website Fingerprinting Defense. Open
Website Fingerprinting (WF) attacks are used by passive, local attackers to determine the destination of encrypted internet traffic by comparing the sequences of packets sent to and received by the user to a previously recorded data set. A…
View article: RegulaTor: A Straightforward Website Fingerprinting Defense
RegulaTor: A Straightforward Website Fingerprinting Defense Open
Website Fingerprinting (WF) attacks are used by local passive attackers to determine the destination of encrypted internet traffic by comparing the sequences of packets sent to and received by the user to a previously recorded data set. As…
View article: <i>p</i><sup>1</sup>-FP: Extraction, Classification, and Prediction of Website Fingerprints with Deep Learning
<i>p</i><sup>1</sup>-FP: Extraction, Classification, and Prediction of Website Fingerprints with Deep Learning Open
Recent advances in Deep Neural Network (DNN) architectures have received a great deal of attention due to their ability to outperform state-of-the-art machine learning techniques across a wide range of application, as well as automating th…
View article: Measuring Information Leakage in Website Fingerprinting Attacks and Defenses
Measuring Information Leakage in Website Fingerprinting Attacks and Defenses Open
Tor provides low-latency anonymous and uncensored network access against a local or network adversary. Due to the design choice to minimize traffic overhead (and increase the pool of potential users) Tor allows some information about the c…
View article: Privacy-Preserving Dynamic Learning of Tor Network Traffic
Privacy-Preserving Dynamic Learning of Tor Network Traffic Open
Experimentation tools facilitate exploration of Tor performance and security research problems and allow researchers to safely and privately conduct Tor experiments without risking harm to real Tor users. However, researchers using these t…
View article: End-to-End Secure Mobile Group Messaging with Conversation Integrity and Minimal Metadata Leakage
End-to-End Secure Mobile Group Messaging with Conversation Integrity and Minimal Metadata Leakage Open
Existing End-to-End secure messaging applications trust a single service provider to deliver messages in a consistent order to a consistent group of conversation members. We propose a protocol that removes this single point of failure by u…
View article: Consistent Synchronous Group Off-The-Record Messaging with SYM-GOTR
Consistent Synchronous Group Off-The-Record Messaging with SYM-GOTR Open
We describe SYM-GOTR, a protocol for secure Group Off-The-Record (GOTR) messaging. In contrast to previous work, SYM-GOTR is the first protocol to offer confidential, authenticated, and repudiable conversations among a dynamic group with t…
View article: CAPTCHA: Using Hard AI Problems for Security
CAPTCHA: Using Hard AI Problems for Security Open
We introduce CAPTCHA, an automated test that humans can pass, but current computer programs can’t pass: any program that has high success over a CAPTCHA can be used to solve an unsolved Artificial Intelligence (AI) problem. We provide seve…