Spoiled Onions: Exposing Malicious Tor Exit Relays

Several hundred Tor exit relays together push more than 1 GiB/s of network traffic. However, it is easy for exit relays to snoop and tamper with anonymised network traffic and as all relays are run by independent volunteers, not all of them are innocuous. In this paper, we seek to expose malicious exit relays and document their actions. First, we monitored the Tor network after developing a fast and modular exit relay scanner. We implemented several scanning modules for detecting common attacks and used them to probe all exit relays over a period of four months. We discovered numerous malicious exit relays engaging in different attacks. To reduce the attack surface users are exposed to, we further discuss the design and implementation of a browser extension patch which fetches and compares suspicious X.509 certificates over independent Tor circuits. Our work makes it possible to continuously monitor Tor exit relays. We are able to detect and thwart many man-in-the-middle attacks which makes the network safer for its users. All our code is available under a free license

Development of a strategy for fire blight control in organic fruit growing

Effective control strategies are needed in organic fruit growing to prevent blossom infections by the fire blight pathogen Erwinia amylovora. There are many potential control agents under discussion. 18 preparations have been tested for their efficiency against Erwinia amylovora. Twelve of them were highly effective against E. amylovora in vitro. Nevertheless only five of them led to a symptom reduction of more than 50% on de-tached apple blossoms. These results and data on field performance from the literature indicate that Blos-som-Protect is the most effective preparation to prevent blossom infections by fire blight. Therefore further experiments have been performed to develop a strategy for the use of Blossom-Protect in organic fruit grow-ing. The side effect of Blossom-Protect on fruit russeting was tested in two field trials in 2005. No increase of fruit russet was detected in the varieties `Jonagored` and `Golden Delicious` after 2 or 3 applications of Blossom-Protect during bloom

Universality in antiferromagnetic strange metals

We propose a theory of metals at the spin-density wave quantum critical point in spatial dimension $d=2$. We provide a first estimate of the full set of critical exponents (dynamical exponent $z=2.13$, correlation length $\nu =1.02$, spin susceptibility $\gamma = 0.96$, electronic non-Fermi liquid $\eta^f_\tau = 0.53$, spin-wave Landau damping $\eta^b_\tau = 1.06$), which determine the universal power-laws in thermodynamics and response functions in the quantum-critical regime relevant for experiments in heavy-fermion systems and iron pnictides. We present approximate numerical and analytical solutions of Polchinski-Wetterich type flow equations with soft frequency regulators for an effective action of electrons coupled to spin-wave bosons. Performing the renormalization group in frequency -instead of momentum- space allows to track changes of the Fermi surface shape and to capture Landau damping during the flow. The technique is easily generalizable from models retaining only patches of the Fermi surface to full, compact Fermi surfaces.Comment: 46 pages, 13 figures, typos fixed; as accepted to Physical Review

Growing into and out of Social Conflict

We present a model of growth and distributional conflict that implies a non-monotonic relationship between average wealth and the likelihood of radical redistribution; while the net benefits of redistribution for members of the poor class are small at low stages of development, a shift towards egalitarianism considerably improves agents' income prospects once an intermediate level of per-capita wealth is reached. As the economy grows further, the incentive to challange the existing social order decreases again and eventually vanishes. This nonmonotonicity captures the observation that historical shifts to radically redistributive policies frequently took place after extended periods of economic growth.

An introduction to Markov chains for interested high school students

Markov Chains are introduced by only assuming some knowledge of the notion of probability. The modelling of a situation in a context of biology gives the opportunity to students to approach various concepts of probability theory themselves. --