Strong authentication based on mobile application

The user authentication in online services has evolved over time from the old username and password-based approaches to current strong authentication methodologies. Especially, the smartphone app has become one of the most important forms to perform the authentication. This thesis describes various authentication methods used previously and discusses about possible factors that generated the demand for the current strong authentication approach. We present the concepts and architectures of mobile application based authentication systems. Furthermore, we take closer look into the security of the mobile application based authentication approach. Mobile apps have various attack vectors that need to be taken under consideration when designing an authentication system. Fortunately, various generic software protection mechanisms have been developed during the last decades. We discuss how these mechanisms can be utilized in mobile app environment and in the authentication context. The main idea of this thesis is to gather relevant information about the authentication history and to be able to build a view of strong authentication evolution. This history and the aspects of the evolution are used to state hypothesis about the future research and development. We predict that the authentication systems in the future may be based on a holistic view of the behavioral patterns and physical properties of the user. Machine learning may be used in the future to implement an autonomous authentication concept that enables users to be authenticated with minimal physical or cognitive effort

Energy Efficient Security Framework for Wireless Local Area Networks

Wireless networks are susceptible to network attacks due to their inherentvulnerabilities. The radio signal used in wireless transmission canarbitrarily propagate through walls and windows; thus a wireless networkperimeter is not exactly known. This leads them to be more vulnerable toattacks such as eavesdropping, message interception and modifications comparedto wired-line networks. Security services have been used as countermeasures toprevent such attacks, but they are used at the expense of resources that arescarce especially, where wireless devices have a very limited power budget.Hence, there is a need to provide security services that are energy efficient.In this dissertation, we propose an energy efficient security framework. Theframework aims at providing security services that take into account energyconsumption. We suggest three approaches to reduce the energy consumption ofsecurity protocols: replacement of standard security protocol primitives thatconsume high energy while maintaining the same security level, modification ofstandard security protocols appropriately, and a totally new design ofsecurity protocol where energy efficiency is the main focus. From ourobservation and study, we hypothesize that a higher level of energy savings isachievable if security services are provided in an adjustable manner. Wepropose an example tunable security or TuneSec system, which allows areasonably fine-grained security tuning to provide security services at thewireless link level in an adjustable manner.We apply the framework to several standard security protocols in wirelesslocal area networks and also evaluate their energy consumption performance.The first and second methods show improvements of up to 70% and 57% inenergy consumption compared to plain standard security protocols,respectively. The standard protocols can only offer fixed-level securityservices, and the methods applied do not change the security level. The thirdmethod shows further improvement compared to fixed-level security by reducing(about 6% to 40%) the energy consumed. This amount of energy saving can bevaried depending on the configuration and security requirements

Certificateless Public Key Signature Schemes from Standard Algorithms

Certificateless public key cryptography (CL-PKC) is designed to have succinct public key management without using certificates at the same time avoid the key-escrow attribute in the identity-based cryptography. However, it appears difficult to construct CL-PKC schemes from standard algorithms. Security mechanisms employing self-certified key (also known as implicit certificate) can achieve same goals. But there still lacks rigorous security definitions for implicit-certificate-based mechanisms and such type of schemes were not analyzed formally and often found vulnerable to attacks later. In this work, we first unify the security notions of these two types of mechanisms within an extended CL-PKC formulation. We then present a general key-pair generation algorithm for CL-PKC schemes and use it with the key prefixing technique to construct certificateless public key signature (CL-PKS) schemes from standard algorithms. The security of the schemes is analyzed within the new model, and it shows that the applied technique helps defeat known-attacks against existing constructions. The resulting schemes could be quickly deployed based on the existing standard algorithm implementations. They are particularly useful in the Internet of Things (IoT) to provide security services such as entity authentication, data integrity and non-repudiation because of their low computation cost, bandwidth consumption and storage requirement

Privacy Preserving Cryptographic Protocols for Secure Heterogeneous Networks

Disertační práce se zabývá kryptografickými protokoly poskytující ochranu soukromí, které jsou určeny pro zabezpečení komunikačních a informačních systémů tvořících heterogenní sítě. Práce se zaměřuje především na možnosti využití nekonvenčních kryptografických prostředků, které poskytují rozšířené bezpečnostní požadavky, jako je například ochrana soukromí uživatelů komunikačního systému. V práci je stanovena výpočetní náročnost kryptografických a matematických primitiv na různých zařízeních, které se podílí na zabezpečení heterogenní sítě. Hlavní cíle práce se zaměřují na návrh pokročilých kryptografických protokolů poskytujících ochranu soukromí. V práci jsou navrženy celkově tři protokoly, které využívají skupinových podpisů založených na bilineárním párování pro zajištění ochrany soukromí uživatelů. Tyto navržené protokoly zajišťují ochranu soukromí a nepopiratelnost po celou dobu datové komunikace spolu s autentizací a integritou přenášených zpráv. Pro navýšení výkonnosti navržených protokolů je využito optimalizačních technik, např. dávkového ověřování, tak aby protokoly byly praktické i pro heterogenní sítě.The dissertation thesis deals with privacy-preserving cryptographic protocols for secure communication and information systems forming heterogeneous networks. The thesis focuses on the possibilities of using non-conventional cryptographic primitives that provide enhanced security features, such as the protection of user privacy in communication systems. In the dissertation, the performance of cryptographic and mathematic primitives on various devices that participate in the security of heterogeneous networks is evaluated. The main objectives of the thesis focus on the design of advanced privacy-preserving cryptographic protocols. There are three designed protocols which use pairing-based group signatures to ensure user privacy. These proposals ensure the protection of user privacy together with the authentication, integrity and non-repudiation of transmitted messages during communication. The protocols employ the optimization techniques such as batch verification to increase their performance and become more practical in heterogeneous networks.

Secure Session Framework: An Identity-based Cryptographic Key Agreement and Signature Protocol

Die vorliegende Dissertation beschäftigt sich mit der Methode der identitätsbasierten Verschlüsselung. Hierbei wird der Name oder die Identität eines Zielobjekts zum Verschlüsseln der Daten verwendet. Diese Eigenschaft macht diese Methode zu einem passenden Werkzeug für die moderne elektronische Kommunikation, da die dort verwendeten Identitäten oder Endpunktadressen weltweit eindeutig sein müssen. Das in der Arbeit entwickelte identitätsbasierte Schlüsseleinigungsprotokoll bietet Vorteile gegenüber existierenden Verfahren und eröffnet neue Möglichkeiten. Eines der Hauptmerkmale ist die komplette Unabhängigkeit der Schlüsselgeneratoren. Diese Unabhängigkeit ermöglicht es, dass verschiedene Sicherheitsdomänen ihr eigenes System aufsetzen können. Sie sind nicht mehr gezwungen, sich untereinander abzusprechen oder Geheimnisse auszutauschen. Auf Grund der Eigenschaften des Protokolls sind die Systeme trotzdem untereinander kompatibel. Dies bedeutet, dass Anwender einer Sicherheitsdomäne ohne weiteren Aufwand verschlüsselt mit Anwendern einer anderen Sicherheitsdomäne kommunizieren können. Die Unabhängigkeit wurde ebenfalls auf ein Signatur-Protokoll übertragen. Es ermöglicht, dass Benutzer verschiedener Sicherheitsdomänen ein Objekt signieren können, wobei auch der Vorgang des Signierens unabhängig sein kann. Neben dem Protokoll wurde in der Arbeit auch die Analyse von bestehenden Systemen durchgeführt. Es wurden Angriffe auf etablierte Protokolle und Vermutungen gefunden, die aufzeigen, ob oder in welchen Situationen diese nicht verwendet werden sollten. Dabei wurde zum einen eine komplett neue Herangehensweise gefunden, die auf der (Un-)Definiertheit von bestimmten Objekten in diskreten Räumen basiert. Zum anderen wurde die bekannte Analysemethode der Gitterreduktion benutzt und erfolgreich auf neue Bereiche übertragen. Schlussendlich werden in der Arbeit Anwendungsszenarien für das Protokoll vorgestellt, in denen dessen Vorteile besonders relevant sind. Das erste Szenario bezieht sich auf Telefonie, wobei die Telefonnummer einer Zielperson als Schlüssel verwendet. Sowohl GSM-Telefonie als auch VoIP-Telefonie werden in der Arbeit untersucht. Dafür wurden Implementierungen auf einem aktuellen Mobiltelefon durchgeführt und bestehende VoIP-Software erweitert. Das zweite Anwendungsbeispielsind IP-Netzwerke. Auch die Benutzung der IP-Adresse eines Rechners als Schlüssel ist ein gutes Beispiel, jedoch treten hier mehr Schwierigkeiten auf als bei der Telefonie. Es gibt beispielsweise dynamische IP-Adressen oder die Methode der textit{Network Address Translation}, bei der die IP-Adresse ersetzt wird. Diese und weitere Probleme wurden identifiziert und jeweils Lösungen erarbeitet

Automatic generation of high speed elliptic curve cryptography code

Apparently, trust is a rare commodity when power, money or life itself are at stake. History is full of examples. Julius Caesar did not trust his generals, so that: ``If he had anything confidential to say, he wrote it in cipher, that is, by so changing the order of the letters of the alphabet, that not a word could be made out. If anyone wishes to decipher these, and get at their meaning, he must substitute the fourth letter of the alphabet, namely D, for A, and so with the others.'' And so the history of cryptography began moving its first steps. Nowadays, encryption has decayed from being an emperor's prerogative and became a daily life operation. Cryptography is pervasive, ubiquitous and, the best of all, completely transparent to the unaware user. Each time we buy something on the Internet we use it. Each time we search something on Google we use it. Everything without (almost) realizing that it silently protects our privacy and our secrets. Encryption is a very interesting instrument in the "toolbox of security" because it has very few side effects, at least on the user side. A particularly important one is the intrinsic slow down that its use imposes in the communications. High speed cryptography is very important for the Internet, where busy servers proliferate. Being faster is a double advantage: more throughput and less server overhead. In this context, however, the public key algorithms starts with a big handicap. They have very bad performances if compared to their symmetric counterparts. Due to this reason their use is often reduced to the essential operations, most notably key exchanges and digital signatures. The high speed public key cryptography challenge is a very practical topic with serious repercussions in our technocentric world. Using weak algorithms with a reduced key length to increase the performances of a system can lead to catastrophic results. In 1985, Miller and Koblitz independently proposed to use the group of rational points of an elliptic curve over a finite field to create an asymmetric algorithm. Elliptic Curve Cryptography (ECC) is based on a problem known as the ECDLP (Elliptic Curve Discrete Logarithm Problem) and offers several advantages with respect to other more traditional encryption systems such as RSA and DSA. The main benefit is that it requires smaller keys to provide the same security level since breaking the ECDLP is much harder. In addition, a good ECC implementation can be very efficient both in time and memory consumption, thus being a good candidate for performing high speed public key cryptography. Moreover, some elliptic curve based techniques are known to be extremely resilient to quantum computing attacks, such as the SIDH (Supersingular Isogeny Diffie-Hellman). Traditional elliptic curve cryptography implementations are optimized by hand taking into account the mathematical properties of the underlying algebraic structures, the target machine architecture and the compiler facilities. This process is time consuming, requires a high degree of expertise and, ultimately, error prone. This dissertation' ultimate goal is to automatize the whole optimization process of cryptographic code, with a special focus on ECC. The framework presented in this thesis is able to produce high speed cryptographic code by automatically choosing the best algorithms and applying a number of code-improving techniques inspired by the compiler theory. Its central component is a flexible and powerful compiler able to translate an algorithm written in a high level language and produce a highly optimized C code for a particular algebraic structure and hardware platform. The system is generic enough to accommodate a wide array of number theory related algorithms, however this document focuses only on optimizing primitives based on elliptic curves defined over binary fields

Interdomain User Authentication and Privacy

This thesis looks at the issue of interdomain user authentication, i.e. user authentication in systems that extend over more than one administrative domain. It is divided into three parts. After a brief overview of related literature, the first part provides a taxonomy of current approaches to the problem. The taxonomy is first used to identify the relative strengths and weaknesses of each approach, and then employed as the basis for putting into context four concrete and novel schemes that are subsequently proposed in this part of the thesis. Three of these schemes build on existing technology; the first on 2nd and 3rd-generation cellular (mobile) telephony, the second on credit/debit smartcards, and the third on Trusted Computing. The fourth scheme is, in certain ways, different from the others. Most notably, unlike the other three schemes, it does not require the user to possess tamper-resistant hardware, and it is suitable for use from an untrusted access device. An implementation of the latter scheme (which works as a web proxy) is also described in this part of the thesis. As the need to preserve one’s privacy continues to gain importance in the digital world, it is important to enhance user authentication schemes with properties that enable users to remain anonymous (yet authenticated). In the second part of the thesis, anonymous credential systems are identified as a tool that can be used to achieve this goal. A formal model that captures relevant security and privacy notions for such systems is proposed. From this model, it is evident that there exist certain inherent limits to the privacy that such systems can offer. These are examined in more detail, and a scheme is proposed that mitigates the exposure to certain attacks that exploit these limits in order to compromise user privacy. The second part of the thesis also shows how to use an anonymous credential system in order to facilitate what we call ‘privacy-aware single sign-on’ in an open environment. The scheme enables the user to authenticate himself to service providers under separate identifier, where these identifiers cannot be linked to each other, even if all service providers collude. It is demonstrated that the anonymity enhancement scheme proposed earlier is particularly suited in this special application of anonymous credential systems. Finally, the third part of the thesis concludes with some open research questions