Analysis of linear relationships in block ciphers

This thesis is devoted to the study of linear relationships in symmetric block ciphers. A block cipher is designed so that the ciphertext is produced as a nonlinear function of the plaintext and secret master key. However, linear relationships within the cipher can still exist if the texts and components of the cipher are manipulated in a number of ways, as shown in this thesis. There are four main contributions of this thesis. The first contribution is the extension of the applicability of integral attacks from word-based to bitbased block ciphers. Integral attacks exploit the linear relationship between texts at intermediate stages of encryption. This relationship can be used to recover subkey bits in a key recovery attack. In principle, integral attacks can be applied to bit-based block ciphers. However, specific tools to define the attack on these ciphers are not available. This problem is addressed in this thesis by introducing a refined set of notations to describe the attack. The bit patternbased integral attack is successfully demonstrated on reduced-round variants of the block ciphers Noekeon, Present and Serpent. The second contribution is the discovery of a very small system of equations that describe the LEX-AES stream cipher. LEX-AES is based heavily on the 128-bit-key (16-byte) Advanced Encryption Standard (AES) block cipher. In one instance, the system contains 21 equations and 17 unknown bytes. This is very close to the upper limit for an exhaustive key search, which is 16 bytes. One only needs to acquire 36 bytes of keystream to generate the equations. Therefore, the security of this cipher depends on the difficulty of solving this small system of equations. The third contribution is the proposal of an alternative method to measure diffusion in the linear transformation of Substitution-Permutation-Network (SPN) block ciphers. Currently, the branch number is widely used for this purpose. It is useful for estimating the possible success of differential and linear attacks on a particular SPN cipher. However, the measure does not give information on the number of input bits that are left unchanged by the transformation when producing the output bits. The new measure introduced in this thesis is intended to complement the current branch number technique. The measure is based on fixed points and simple linear relationships between the input and output words of the linear transformation. The measure represents the average fraction of input words to a linear diffusion transformation that are not effectively changed by the transformation. This measure is applied to the block ciphers AES, ARIA, Serpent and Present. It is shown that except for Serpent, the linear transformations used in the block ciphers examined do not behave as expected for a random linear transformation. The fourth contribution is the identification of linear paths in the nonlinear round function of the SMS4 block cipher. The SMS4 block cipher is used as a standard in the Chinese Wireless LAN Wired Authentication and Privacy Infrastructure (WAPI) and hence, the round function should exhibit a high level of nonlinearity. However, the findings in this thesis on the existence of linear relationships show that this is not the case. It is shown that in some exceptional cases, the first four rounds of SMS4 are effectively linear. In these cases, the effective number of rounds for SMS4 is reduced by four, from 32 to 28. The findings raise questions about the security provided by SMS4, and might provide clues on the existence of a flaw in the design of the cipher.

Teaching motor racing engineering through real-life projects: benefits and challenges

Project-based learning (PBL) is widely used in engineering courses. The closer to real-life the project, the greater the relevance and depth of learning experienced by students. Formula Society of Automotive Engineering (FSAE) is a fine example of a team-based project modelled on real-life problems whereby each student team designs and builds a small race car for competitive evaluation. Queensland University of Technology (QUT) has participated in FSAE-Australia since 2004. Based on the success of the project, QUT has gone the additional step of introducing a motor-racing specialization (second major) to complement its mechanical engineering degree. In this paper, the benefits of teaching motor-racing engineering through real-life projects are presented together with a discussion of the challenges faced and how they have been addressed. In order to validate the authors' observations on the teaching approaches used, student feedback was solicited through QUT's online learning experience survey (LEX), as well as a customized paper-based survey. The results of the surveys are analysed and discussed in this paper.

Teaching tribology and maintenance-related subjects : a hands-on focus

In this paper different aspects of teaching tribology and maintenance-related subjects with a hands-on focus at Queensland University of Technology (QUT) are presented and discussed. As part of the study, a combination of data from core units, such as engineering design units, and elective units, was used, in addition to laboratory experiments, real-life projects, interactive software packages and industry visits. The mechanical engineering curriculum structure used at QUT, consisting of the main specialization (first major) and the second specialization (second major), is also discussed with specific emphasis on the teaching of tribology and maintenance-related subjects. To evaluate students' satisfaction with the novel teaching approaches used, tailored questionnaires were used as well as QUT's online learning experience survey (LEX). Statistical results of these sureveys are presented and discussed. In summary, these showed that students overwhelmingly support the hands-on and practical focus in teaching tribology and maintenance-related subjects and that the teaching approaches used shorten the learning curve and make students better prepared for integration in the workplace.

Who owns Superman? The Man of Steel fights trademark law

Who is Superman’s greatest threat? Evil genius Lex Luthor? General Zod from the Phantom Zone? The doppelganger Bizarro? Super-villain Brainiac? Kryptonite? Or is it intellectual property law?

Grant application: QUT Learning and Teaching scheme 2012 Cracking the Code - A checklist to complement CRAs for first year Justice students.

Widening participation brings with it increasing diversity, increased variation in the level of academic preparedness (Clarke, 2011; Nelson, Clarke, & Kift 2010). Cultural capital coupled with negotiating the academic culture creates an environment based on many assumptions about academic writing and university culture. Variations in staff and student expectations relating to the teaching and learning experience is captured in a range of national and institutional data (AUSSE, CEQ, LEX). Nationally, AUSSE data (2009) indicates that communication, writing, speaking and analytic skills, staff expectations are quite a bit higher than students. The research team noted a recognisable shift in the changing cohort of students and their understanding and engagement with feedback and CRAs, as well as variations in teaching staff and student expectations. The current reality of tutor and student roles is that: - Students self select when/how they access lectures and tutorials. - Shorter tutorial times result in reduced opportunity to develop rapport with students. - CRAs are not always used consistently by staff (different marking styles and levels of feedback). - Marking is not always undertaken by the student’s tutor/lecturer. - Student support services might be recommended to students once a poor grade has been given. Students can perceive this as remedial and a further sense of failure. - CRA sheet has a mark /grade attached to it. Stigma attached to low mark. Hard to focus on the CRA feedback with a poor mark etched next to it. - Limited opportunities for sessionals to access professional development to assist with engaging students and feedback. - FYE resources exist, however academic time is a factor in exploring and embedding these resources. Feedback is another area with differing expectations and understandings. Sadler (2009) contends that students are not equipped to decode the statements properly. For students to be able to apply feedback, they need to understand the meaning of the feedback statement. They also need to identify, the particular aspects of their work that need attention. The proposed Checklist/guide would be one page and submitted with each assessment piece thereby providing an interface to engage students and tutors in managing first year understandings and expectations around CRAs, feedback, and academic practice.

Use of tea tree oil against buffalo flies in cattle

Testing tea tree oil against buffalo flies on cattle.

Auktoriteetin ja järjen suhde Augustinuksen varhaisissa manikealaisvastaisissa teoksissa

Tutkielman tehtävänä on selvittää jumalallisen auktoriteetin (auctoritas divina) ja ihmisen järjen (ratio) välinen suhde Augustinuksen tietoteoriassa. Päälähteinä käytetään kolmea Augustinuksen varhaistuotannon manikealaisvastaista teosta De moribus ecclesiae catholicae et de moribus manichaeorum, De vera religione ja De utilitate credendi. Tutkielman metodina on systemaattinen analyysi. Tutkimustehtävä sisältää alakysymyksiä: Kuinka käsitepari auktoriteetti - järki suhteutuu käsitepariin uskominen (credere) - ymmärtäminen (intellegere)? Mitkä ovat järjen kyvyt, rajat ja tehtävät? Mikä on auktoriteetin tehtävä ja miksi auktoriteetteja tarvitaan? Missä määrin päälähteiden välillä on eroja? Luvussa 2 tarkastellaan sitä uskonnollis-filosofista taustaa, jonka kautta Augustinuksen käsitys auktoriteetin ja järjen suhteesta tulee ymmärrettäväksi. Vaikka Augustinus liittyykin uskon ja ymmärryksen suhteen varhaiskristilliseen traditioon, ei hänen käsitystään voida ymmärtää irrallaan platonilaisesta ja uusplatonilaisesta tietoteoriasta. Augustinuksen tietoteoria muotoutui myös vastauksessa skeptisismiin ja manikealaiseen pseudo-rationalismiin. Pääluvuissa 3, 4 ja 5 käsitellään Augustinuksen käsitystä auktoriteetin ja järjen suhteesta siten, että kussakin pääluvussa keskitytään yhteen päälähteeseen. Loppukatsauksessa (luku 6) kootaan yhteen tutkimuksen tulokset. Augustinuksen klassisesta roomalaisesta kirjallisuudesta lanseeraama käsitepari auktoriteetti - järki liittyy läheisesti toiseen käsitepariin uskominen - ymmärtäminen. Usko perustuu auktoriteettiin ja ymmärrys järkeen. Niin kuin usko edeltää ymmärrystä (credo ut intelligam), samoin auktoriteetti edeltää uskoa. Mutta toisaalta myös ymmärrys edeltää uskoa siinä mielessä, että on ymmärrettävä auktoriteetin ilmoittamat väitelauseet, jotta usko tulisi mahdolliseksi. Tietyssä mielessä myös järki edeltää auktoriteettia, sillä järki arvioi, kuka on uskomisen arvoinen. Ilman auktoriteettiin perustuvaa uskoa ihminen kykenee järjen avulla tajuamaan ainakin yhden totuuden, nimittäin sen, että kaiken epäileminen on mahdotonta. Radikaaleinkin epäilijä on varma ainakin siitä totuudesta, että hän epäilee. Augustinus antaa toisinaan ymmärtää, että ilman auktoriteettia voidaan käsittää myös Jumalan olemassaolo. Toisinaan hän taas opettaa, että tieto Jumalan olemassaolosta perustuu jumalalliseen auktoriteettiin. Ihmisen järki on rajallinen kahdessa mielessä. Ensinnäkin se ei kykene saavuttamaan varmaa tietoa aistimaailman ajallisista asioista. Varma tieto eli ymmärrys kohdistuu vain ikuisiin ja intelligiibeleihin totuuksiin. Toiseksi ihmisen järki on osallinen syntiinlankeemuksesta niin, että totuuden tavoittaminen tulee lopulta mahdottomaksi ilman auktoriteettia. Jumalallinen auktoriteetti on Augustinuksen mukaan Kristuksessa, Raamatussa ja katolisessa kirkossa. Jumalallinen auktoriteetti ilmoittaa pelastushistorian totuudet, joiden kautta ihmisen mieli puhdistuu ja kykenee kohoamaan kohti ikuisia jumalallisia totuuksia. Jumalallisen auktoriteetin ilmoittamat ikuiset totuudet ovat luonteeltaan sellaisia, että niihin on ensin uskottava, jotta ne voitaisiin myöhemmin ymmärtää (credo, quod intelligam). Auktoriteetin tehtävä on johdattaa järkeen ja järjen tehtävä on johtaa ymmärrykseen. Teoksen päälähteet opettavat pääsääntöisesti samalla tavalla käsillä olevasta aiheesta. De moribuksessa painopiste on tosin muita selkeämmin rakkaudessa: rakkaus johtaa tietoteoreettiseen täyttymykseen. De vera religionessa on vahvimpana ajatus luonnollisesta jumalatuntemuksesta. De utilitate credendi keskittyy voimakkaimmin auktoriteettiuskon puolustamiseen. Päälähteiden painotuserot johtuvat niiden erilaisesta luonteesta.

Las citas de leyes y otras normas : legislación comparada y nuevo digesto jurídico argentino

Decía Tomás de Aquino que “lex non est ipsum ius, proprie loquendo, sed aliqualis ratio iuris” 1: “[…] la ley no es el mismo derecho, propiamente hablando, sino cierta racionalización del derecho”. En concordancia con esto, entre nosotros enseñaba Alberdi que “saber, pues, leyes, no es saber derecho”, dado que “las leyes no son más que la imagen imperfecta y frecuentemente desleal del derecho que vive en la armonía viva del organismo social”, del cual hay que “conocer su genio, su misión, su rol”, porque “es el alma, la vida, el espíritu de las leyes” 2. Esto lleva, según el maestro argentino, a que “en materia de leyes, no se puede hacer nada, si no se sabe el derecho”3. El derecho no es la ley, entonces, pero sin embargo la ley tiene una relación estrecha con el derecho, del cual a veces es su causa eficiente, como ocurre con las materias de mero Derecho Positivo, y otras, es una suerte de causa ejemplar, cuando refleja la justicia natural de las cosas. La causa final inmediata de toda ley, por otra parte, debe ser el derecho, y la mediata, el bien común. El hecho, entonces, de que las leyes tengan una función segunda con respecto al derecho no las vuelve menos importantes. El conocimiento de las leyes, así, no es algo ajeno al oficio del jurista, sino que es un elemento fundamental para la búsqueda de la justicia en los casos concretos...

In Their Own Words

In Their Own Words, one in a series of Effective Practice guides, explores the under-researched and imperfectly understood world of the learner in a digital age by synthesising outcomes from the first phase of the Learner Experiences of e-Learning theme of the JISC e-Learning Programme. These outcomes include a scoping study and literature review, a methodology report and two studies – LEX: The Learner Experience of e-Learning (Creanor et al., 2006) and LXP: Student Experiences of e-Learning (Conole et al., 2006), plus five video case studies of experiences of e-learning recounted by learners themselves.

Influência de agentes clareadores na rugosidade de compósitos dentários

O clareamento dental é o meio disponível mais simples, comum e conservador para o cirurgião-dentista proporcionar aos pacientes o padrão de cor de seus dentes mais desejado. Em alguns casos, os dentes que vão ser clareados podem apresentar restaurações realizadas com compósitos dentais, que são mais suscetíveis a alterações químicas, quando comparados a outros materiais restauradores. Alguns estudos mostraram que diferentes concentrações de agentes clareadores levaram a um aumento significativo da rugosidade superficial e das porosidades em compósitos dentais. Este estudo avaliou o efeito de dois agentes clareadores (Whiteness HP Blue 20%, Whiteness HP Max) sobre a rugosidade superficial de dois compósitos dentais, um micro-híbrido (Esthet X, Denstply) e outro nanoparticulado (Z 350, 3M ESPE). Um total de oito corpos de prova (9 x 2 mm) foram confeccionados com auxílio de uma matriz de teflon, sendo divididos em 4 grupos (Esthet X + Whiteness HP Blue 20%; Esthet X + Whiteness HP Max; Z 350 + Whiteness HP Blue 20%; Z 350 + Whiteness HP Max), sendo n=2. Os corpos de prova foram armazenados em saliva artificial neutra e, após 24 horas, foram polidos com discos de óxido de Alumínio (Sof-lex, 3M ESPE). Após sete dias de imersão salivar, cada corpo de prova foi levado a um microscópio de força atômica para obtenção do valor inicial de rugosidade superficial (Ra em nm). Em seguida, sem remover o corpo de prova do microscópio, o agente clareador foi aplicado sobre a superfície do corpo de prova, segundo as instruções do fabricante, de modo que permitisse uma posterior observação da mesma área do corpo de prova observada inicialmente, para obtenção do valor final de rugosidade superficial. Imagens em duas e três dimensões foram obtidas de cada corpo de prova para observação de alterações da topografia. Os resultados foram tratados estatisticamente por ANOVA e pelo teste de contraste Student-Newman-Keuls (p < 0,05). Não houve alteração significativa na rugosidade superficial (Ra) dos corpos da prova de compósitos micro-híbrido e nanoparticulado, submetidos aos agentes clareadores Whiteness HP Blue 20% e Whiteness HP Maxx. No entanto, independente do agente clareador utilizado, foram observadas maiores alterações topográficas nas imagens de microscopia de força atômica da superfície do compósito micro-híbrido do que nas imagens do nanoparticulado.

A prescrição no direito internacional privado brasileiro

Este trabalho trata do funcionamento da prescrição extintiva relacionada a ações pessoais, além da decadência, no âmbito do direito internacional privado. Primeiramente é feita uma breve análise histórica e comparatista do direito de regência da prescrição em relações de caráter internacional antes de se demonstrar a solução abarcada pelo direito brasileiro: a regência pela lei que rege a obrigação (lex causae). Apesar de ser um instituto de direito civil, substantivo, a prescrição possui muitas ligações com o direito processual, uma vez que o principal efeito de sua consumação é tonar inexigível uma obrigação e, em decorrência, pôr fim a um processo. Assim, o autor detalha em seguida as questões que são regidas pela lex causae e as que são regidas pela lex fori (aqui abrangendo também a lex arbitri) em matéria de prescrição no direito brasileiro, antes de tratar minuciosamente de como se opera a exceção da ordem pública para afastar a aplicação da lex causae estrangeira em matéria de prescrição no Brasil (incluindo também regras de aplicação imediata lois de police brasileiras). Ao final, cuida-se da prescrição na homologação e execução de sentenças estrangeiras no Brasil.