Sanitizable signatures allow for controlled modification of signed data. The essential security requirements are accountability, privacy and unlinkability. Unlinkability is a strong notion of privacy. Namely, it makes it hard to link two sanitized messages that were derived from the same message-signature pair. In this work, we strengthen the standard unlinkability definition by Brzuska et al. ...

We consider a simple model of an autocatalytic chemical reaction where a limit cycle rapidly increases to infinite period and amplitude, and disappears under variation of a parameter. We show that this bifurcation can be understood from seeing the system as a singular perturbation problem, and we find the bifurcation point by an asymptotic analysis. Scaling laws for period and amplitude are der...

This paper presents a detailed analysis of mixed-mode oscillations in the “autocatalator,” a threedimensional, two time scale vector field that is a chemical reactor model satisfying the law of mass action. Unlike earlier work, this paper investigates a return map that simultaneously exhibits full rank and rank deficient behavior in different regions of a cross section. Canard trajectories that...

The occurrence of spatial domains of large amplitude oscillation on a background of small amplitude oscillation in a reaction–diffusion system is called localization. We study, analytically and numerically, the mechanism of localization in a model of the Belousov–Zhabotinsky reaction subject to global feedback. This behavior is found to arise from the canard phenomenon, in which a limit cycle s...

Abstract Stellate cells (SCs) of the medial entorhinal cortex (layer II) display mixed-mode oscillatory activity, subthreshold oscillations (small amplitude) interspersed with spikes (large amplitude), at theta frequencies (8 12 Hz). In this paper we study the mechanism of generation of such patterns in a SC biophysical (conductance-based) model. In particular, we show that the mechanism is bas...

Many natural and technological systems fail to adapt to changing external conditions and move to a different state if the conditions vary too fast. Such 'non-adiabatic' processes are ubiquitous, but little understood. We identify these processes with a new nonlinear phenomenon-an intricate threshold where a forced system fails to adiabatically follow a changing stable state. In systems with mul...

Electronic cash (e-cash) refers to money exchanged electronically. The main features of traditional cash are usually considered desirable also in the context of e-cash. One such property is off-line transferability, meaning the recipient of a coin in a transaction can transfer it in a later payment transaction to a third person without contacting a central authority. Among security properties, ...

Entorhinal cortex layer II stellate cells display subthreshold oscillations (STOs). We study a single compartment biophysical model of such cells which qualitatively reproduces these STOs. We argue that in the interspike interval (ISI) the seven-dimensional model can be reduced to a three-dimensional system of equations with well differentiated times scales. Using dynamical systems arguments we...

The peculiar head morphology of hammerhead sharks has spawned a variety of untested functional hypotheses. One of the most intuitively appealing ideas is that the anterior foil acts, as in canard-winged aircraft, to increase maneuverability. We tested this hypothesis by determining whether juveniles of two hammerhead species (Sphyrna tiburo and S. lewini) turn more sharply, more often, and with...