07021 Abstracts Collection -- Symmetric Cryptography

From .. to .., the Dagstuhl Seminar 07021 ``Symmetric Cryptography\u27\u27 automatically was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Deploying a New Hash Algorithm

The strength of hash functions such as MD5 and SHA-1 has been called into question as a result of recent discoveries. Regardless of whether or not it is necessary to move away from those now, it is clear that it will be necessary to do so in the not-too-distant future. This poses a number of challenges, especially for certificate-based protocols. We analyze a number of protocols, including S/MIME and TLS. All require protocol or implementation changes. We explain the necessary changes, show how the conversion can be done, and list what measures should be taken immediately

Cryptanalysis and Design of Symmetric Primitives

Der Schwerpunkt dieser Dissertation liegt in der Analyse und dem Design von Block- chiffren und Hashfunktionen. Die Arbeit beginnt mit einer Einführung in Techniken zur Kryptoanalyse von Blockchiffren. Wir beschreiben diese Methoden und zeigen wie man daraus neue Techniken entwickeln kann, welche zu staerkeren Angriffen fuehren. Im zweiten Teil der Arbeit stellen wir eine Reihe von Angriffen auf eine Vielzahl von Blockchiffren dar. Wir haben dabei Angriffe auf reduzierte Versionen von ARIA und dem AES entwickelt. Darueber hinaus praesentieren wir im dritten Teil Angriffe auf interne Blockchiffren von Hashfunktionen. Wir entwickeln Angriffe, welche die inter- nen Blockchiffren von Tiger und HAS-160 auf volle Rundenanzahl brechen. Die hier vorgestellten Angriffe sind die ersten dieser Art. Ein Angriff auf eine reduzierte Ver- sion von SHACAL-2 welcher fast keinen Speicherbedarf hat, wird ebenfalls vorgestellt. Der vierte Teil der Arbeit befasst sich mit den Design und der Analyse von kryp- tographischen Hashfunktionen. Wir habe einen Slide Angriff, eine Technik welche aus der Analyse von Blockchiffren bekannt ist, im Kontext von Hashfunktionen zur Anwendung gebracht. Dabei praesentieren wir verschiedene Angriffe auf GRINDAHL und RADIOGATUN. Aufbauend auf den Angriffen des zweiten und dritten Teils dieser Arbeit stellen wir eine neue Hashfunktion vor, welche wir TWISTER nennen. TWISTER wurde fuer den SHA-3 Wettbewerb entwickelt und ist bereits zur ersten Runde angenommen.This thesis focuses on the cryptanalysis and the design of block ciphers and hash func- tions. The thesis starts with an overview of methods for cryptanalysis of block ciphers which are based on differential cryptanalysis. We explain these concepts and also sev- eral combinations of these attacks. We propose new attacks on reduced versions of ARIA and AES. Furthermore, we analyze the strength of the internal block ciphers of hash functions. We propose the first attacks that break the internal block ciphers of Tiger, HAS-160, and a reduced round version of SHACAL-2. The last part of the thesis is concerned with the analysis and the design of cryptographic hash functions. We adopt a block cipher attack called slide attack into the scenario of hash function cryptanalysis. We then use this new method to attack different variants of GRINDAHL and RADIOGATUN. Finally, we propose a new hash function called TWISTER which was designed and pro- posed for the SHA-3 competition. TWISTER was accepted for round one of this com- petition. Our approach follows a new strategy to design a cryptographic hash function. We also describe several attacks on TWISTER and discuss the security issues concern- ing these attack on TWISTER

Visual Adaptations and Behavioural Strategies to Detect and Catch Small Targets

Predatory behaviours are ideal for studying the limits of performance and control within animals. Predation naturally creates a competition between the sensors and physiology of predator and prey. Aerial predation demonstrates the greatest feats of physical performance, demanding the highest speeds and accelerations whilst both predator and prey are free to pitch, yaw, and roll. These high speeds and degrees of rotational freedom make control a complex problem. However, from the perspective of the researcher attempting to decipher the control laws that underpin predator guidance, the question is made more soluble by the predator’s fixation on its target. The goal of the pursuer is clear, to contact the target, and thus their systems are focused on the optimization of that action. This is as opposed to more mundane activities, where conflicting interests compete for the attention and behavioural response of the animal. In order to study the necessary trade-offs that underpin aerial predation, this thesis will focus on the hunting behaviour of two fly species. The first is a robber fly, Holcocephala fusca, on which the majority of the first two chapters focus. Secondarily, work with the killer fly Coenosia attenuata will be included in the latter two chapters as a direct contrast to results from Holcocephala. Both are miniature dipteran predators, but not closely related. The structure of this thesis is broken into six chapters, summarised in the following list: 1. Thecompoundeyeofinsectsgenerallyhasmuchpoorerresolutionthanthatofcameratype eyes. Poor resolution is exacerbated in smaller insects that cannot commit the resources required for eyes with large lenses that facilitate high spatial resolution. Holcocephala has developed a small number of facets into a forward-facing acute zone where the spatial acuity is reduced to ~0.28°, rivalling the very best resolution of any compound eye. The only compound eyes with a comparable spatial resolution belong to dragonflies, in excess of an order of magnitude larger than Holcocephala. 2. Numerous potential targets may be airborne within the visual range of a predator. Not all of these may be suitable. Chasing unsuitable targets may waste energy or result in direct harm should they turn out to be larger than the predator can overcome. It is thus a strong imperative for a predator to filter the targets it takes after. Targets silhouetted against the sky display a paucity of cues that a predator could use to determine their size. Holcocephala displays acute size selectivity towards smaller targets. This selectivity goes beyond heuristic rules and size/speed ratios. Instead, Holcocephala appears able to determine absolute size and distance of targets. 3. Both Holcocephala and Coenosia intercept targets, heading for where the target is going to be in the future rather than its current location. Both species plot trajectories in keeping with the guidance law of proportional navigation, an algorithm derived for modern guided missiles. There are key differences evident in the internal physiological constants applied to the control system between the species. These differences are likely linked to the specific environmental conditions and visual physiologies of the flies, especially the range at which targets are attacked. 4. Stemming from the use of the proportional navigational framework, this chapter dives into the intricacies of gain and the weighting of the navigational constant, and the geometric factors that underpin the control effort and eventual success of the control system. 5. “Falcon-diving” can be found in killer flies dropping from their enclosure ceiling, in which they miss targets after diving towards them. Through proportional navigation, it can be demonstrated that the navigational system combined with excessive speed results in acceleration demands the body cannot match. 6. Holcocephala is capable of evading static obstacle whilst intercepting targets. Application of proportional navigation and a secondary obstacle-evasive controller can demonstrate where the fly is combining multiple inputs to guide its heading.This work was funded by the United States Airforce Office of Scientific Research

2-Dimension Sums: Distinguishers Beyond Three Rounds of RIPEMD-128 and RIPEMD-160

This paper presents differential-based distinguishers against ISO standard hash functions RIPEMD-128 and RIPEMD-160. The compression functions of RIPEMD-128/-160 adopt the double-branch structure, which updates a chaining variable by computing two functions and merging their outputs. Due to the double size of the internal state and difficulties of controlling two functions simultaneously, only few results were published before. In this paper, second-order differential paths are constructed on reduced RIPEMD-128 and -160. This leads to a practical 4-sum attack on 47 steps (out of 64 steps) of RIPEMD-128 and 40 steps (out of 80 steps) of RIPEMD-160. We then extend the distinguished property from the 4-sum to other properties, which we call \emph{a 2-dimension sum} and \emph{a partial 2-dimension sum}. As a result, the practical partial 2-dimension sum is generated on 48 steps of RIPEMD-128 and 42 steps of RIPEMD-160, with a complexity of $2^{35}$ and $2^{36}$, respectively. Theoretically, $2$-dimension sums are generated faster than the exhaustive search up to 52 steps of RIPEMD-128 and 51 steps of RIPEMD-160, with a complexity of $2^{101}$ and $2^{158}$, respectively. The practical attacks are implemented, and examples of generated (partial) 2-dimension sums are presented

Cyber-threats and cybersecurity challenges: A cross-cultural perspective

As is the case of any economic activity, cultural factors are tightly linked to cybercrimes, cyberattacks and cybersecurity. Just like any other activities, some forms of cybercrime may be more acceptable in some cultures than in others. For some categories of cyberoffenses, cultural factors appear to play more important roles than other environmental factors. For instance, cybercrimes are more justifiable in some cultures. Quoting a Russian hacker-turned-teacher, Blau (2004) describes how he and his friends hacked programs and distributed them for free during their childhood: “It was like our donation to society, it was a form of honor; [we were] like Robin Hood bringing programs to people.” Likewise, it is argued that culture and ethical attitudes may be a more crucial factor in driving software piracy as well as a number of other cybercrimes than the levels of economic development (Donaldson, 1996; Kshetri, 2009b, 2013a, b, c, d; Kwong et al., 2003)

The Rebound Attack and Subspace Distinguishers: Application to Whirlpool

We introduce the rebound attack as a variant of differential cryptanalysis on hash functions and apply it to the hash function Whirlpool, standardized by ISO/IEC. We give attacks on reduced variants of the Whirlpool hash function and the Whirlpool compression function. Next, we introduce the subspace problems as generalizations of near-collision resistance. Finally, we present distinguishers based on the rebound attack, that apply to the full compression function of Whirlpool and the underlying block cipher $W$

Personality AI Development

This project is about exploring various methods to create game A.I.s with different personalities. A Japanese themed game Action Role Playing Game is also made for testing the A.I.s. We used three algorithms: behavior tree, behavior tree with utility based decision maker, and finite state machine, and made four A.I.s each with personality of: aggressive, bullying, cowardly and tricky. All the A.I.s is put into an NPC monster called Nue in our game: Yokai World and a test were conducted with 16 play testers to see each personality’s recognizability and believability