Data Poisoning against Differentially-Private Learners: Attacks and Defenses

Data poisoning attacks aim to manipulate the model produced by a learning algorithm by adversarially modifying the training set. We consider differential privacy as a defensive measure against this type of attack. We show that private learners are resistant to data poisoning attacks when the adversary is only able to poison a small number of items. However, this protection degrades as the adversary is allowed to poison more data. We emprically evaluate this protection by designing attack algorithms targeting objective and output perturbation learners, two standard approaches to differentially-private machine learning. Experiments show that our methods are effective when the attacker is allowed to poison sufficiently many training items.

Bemerkungen über die altkeltischen Fluchrituale: Zum Blei von Chartres und einem lateinischen Fluchtäfelchen mit Formeln keltischen Ursprungs

This paper deals with the Gaulish defixio from Chartres and more generally with the Celtic tradition of malediction rituals in Antiquity, as documented by the defixiones from Chartres, Larzac and Chamalières and by contact features in Latin defixiones from the Celtic speaking provinces. It is argued that this tradition, as opposed to the Latin one, systematically advocated that the malediction ritual was performed as a defensive measure against a former malediction by the cursed persons. The same lexemes are used to refer to the cursed persons and to the performer of the cursing ritual: this stylistic device emphasises that the defixio is to be regarded as a counter-malediction.

WAGING WAR IN LATE ANTIQUITY

This paper identifies the decisive factors in the course and outcome of wars in Late Antiquity. While many of these factors are also significant to war in other periods, it is argued that an unprecedented level of fortification work, carried out by successive regimes, was the distinctive characteristic of late antique warfare. Rather than a negative, solely defensive measure, fortress cities, forts, watchtowers and cross walls gave the Romans a platform for aggressive campaigning within and beyond the frontiers of the empire. These defences enabled the Romans to control intelligence, supplies, manpower, and local hearts and minds within campaign arenas.