Trustworthy content push

Delivery of content to mobile devices gains increasing importance in industrial environments to support employees in the field. An important application are e-mail push services like the fashionable Blackberry. These systems are facing security challenges regarding data transport to, and storage of the data on the end user equipment. The emerging Trusted Computing technology offers new answers to these open questions.Comment: 4 pages, 4 eps figure

Non-Repudiation in Internet Telephony

We present a concept to achieve non-repudiation for natural language conversations over the Internet. The method rests on chained electronic signatures applied to pieces of packet-based, digital, voice communication. It establishes the integrity and authenticity of the bidirectional data stream and its temporal sequence and thus the security context of a conversation. The concept is close to the protocols for Voice over the Internet (VoIP), provides a high level of inherent security, and extends naturally to multilateral non-repudiation, e.g., for conferences. Signatures over conversations can become true declarations of will in analogy to electronically signed, digital documents. This enables binding verbal contracts, in principle between unacquainted speakers, and in particular without witnesses. A reference implementation of a secure VoIP archive is exhibited.Comment: Accepted full research paper at IFIP sec2007, Sandton, South Africa, 14-16 May 200

A secure archive for Voice-over-IP conversations

An efficient archive securing the integrity of VoIP-based two-party conversations is presented. The solution is based on chains of hashes and continuously chained electronic signatures. Security is concentrated in a single, efficient component, allowing for a detailed analysis.Comment: 9 pages, 2 figures. (C) ACM, (2006). This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of VSW06, June, 2006, Berlin, German

Themenstudienarbeit

In diesem Buch werden zwei Schwerpunktziele verfolgt. In einem ersten Teil wird die Rahmenkonzeption der Themenstudienarbeit als Lernumgebung im Mathematikunterricht theoretisch fundiert. In einem zweiten Teil wird eine Studie beschrieben, die im Rahmen eines DFG-geförderten Forschungsprojekts durchgeführt wurde und die Evaluation einer Themenstudienarbeit zum Inhaltsbereich des geometrischen Beweisens und Argumentierens zum Gegenstand hatte

Chiral structures of lander molecules on Cu(100)

Supramolecular assemblies of lander molecules (C$_{90}$H$_{98}$) on Cu(100) are investigated with low-temperature scanning tunneling microscopy. The energetically most favourable conformation of the adsorbed molecule is found to exist in two mirror symmetric enantiomers or conformers. At low coverage, the molecules align in enantiomerically pure chains along the chiral directions $[01\bar{2}],[02\bar{1}],[012]$ and $[021]$. The arrangement is proposed to be mainly governed by intermolecular van-der-Waals interaction. At higher coverages, the molecular chains arrange into chiral domains, for which a structural model is presented.Comment: to appear in Nanotechnology vol. 15 (2004

Correlação entre o nível de ansiedade e a presença de dor de cabeça e cansaço muscular facial em estudantes de cursos pré-vestibular localizados na grande Florianópolis

TCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Odontologia.Introdução: A Disfunção temporomandibular (DTM) tem se tornado cada vez mais frequente entre os indivíduos. Estudos epidemiológicos apontam que 40% a 75% da população apresentam pelo menos um sinal de DTM. A sua etiologia é complexa e multifatorial, sendo resultante de vários fatores que agem em conjunto, dentre estes estão os fatores psicológicos como ansiedade e depressão. Objetivo: O presente estudo teve como objetivo identificar a correlação entre o nível de ansiedade e a presença de cefaleia e cansaço muscular na face em estudantes matriculados em cursos pré-vestibular da grande Florianópolis. Metodologia: A partir de uma amostra por conveniência foi aplicada a escala de ansiedade-estado de (SPIELBERGER et al., 2003), a fim de mensurar o nível de ansiedade dos pré-vestibulandos e o questionário de Disfunção Temporomandibular (DTM) visando avaliar a presença e frequência de dor de cabeça e cansaço muscular nos estudantes. Conclusão: Com base nos resultados constatou-se a existência de uma correlação significativa entre o nível de ansiedade e presença de dor de cabeça e dor e/ou cansaço facial em vestibulandos, sendo que a grande maioria dos alunos apresentou grau de ansiedade moderado

Dependence of the elastic strain coefficient of copper on the pre-treatment

The effect of various pre-treatments on the elastic strain coefficient (alpha) (defined as the reciprocal of the modulus of elasticity E) (Epsilon) and on the mechanical hysteresis of copper has been investigated. Variables comprising the pre-treatments were pre-straining by stretching in a tensile testing machine and by drawing through a die, aging at room and elevated temperatures and annealing. The variation of the elastic strain coefficient with test stress was also investigated