| 1. |
- Abidin, Aysajan, 1983-
(författare)
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Authentication in Quantum Key Distribution : Security Proof and Universal Hash Functions
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum Key Distribution (QKD) is a secret key agreement technique that consists of two parts: quantum transmission and measurement on a quantum channel, and classical post-processing on a public communication channel. It enjoys provable unconditional security provided that the public communication channel is immutable. Otherwise, QKD is vulnerable to a man-in-the-middle attack. Immutable public communication channels, however, do not exist in practice. So we need to use authentication that implements the properties of an immutable channel as well as possible. One scheme that serves this purpose well is the Wegman-Carter authentication (WCA), which is built upon Almost Strongly Universal2 (ASU2) hashing. This scheme uses a new key in each authentication attempt to select a hash function from an ASU2 family, which is then used to generate the authentication tag for a message.The main focus of this dissertation is on authentication in the context of QKD. We study ASU2 hash functions, security of QKD that employs a computationally secure authentication, and also security of authentication with a partially known key. Specifically, we study the following.First, Universal hash functions and their constructions are reviewed, and as well as a new construction of ASU2 hash functions is presented. Second, security of QKD that employs a specific computationally secure authentication is studied. We present detailed attacks on various practical implementations of QKD that employs this authentication. We also provide countermeasures and prove necessary and sufficient conditions for upgrading the security of the authentication to the level of unconditional security. Third, Universal hash function based multiple authentication is studied. This uses a fixed ASU2 hash function followed by one-time pad encryption, to keep the hash function secret. We show that the one-time pad is necessary in every round for the authentication to be unconditionally secure. Lastly, we study security of the WCA scheme, in the case of a partially known authentication key. Here we prove tight information-theoretic security bounds and also analyse security using witness indistinguishability as used in the Universal Composability framework.
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| 2. |
- Abidin, Aysajan
(författare)
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Weaknesses of Authentication in Quantum Cryptography and Strongly Universal Hash Functions
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Authentication is an indispensable part of Quantum Cryptography, which is an unconditionally secure key distribution technique based on the laws of nature. Without proper authentication, Quantum Cryptography is vulnerable to “man-in-the-middle” attacks. Therefore, to guarantee unconditional security of any Quantum Cryptographic protocols, the authentication used must also be unconditionally secure. The standard in Quantum Cryptography is to use theWegman-Carter authentication, which is unconditionally secure and is based on the idea of universal hashing.In this thesis, we first investigate properties of a Strongly Universal hash function family to facilitate understanding the properties of (classical) authentication used in Quantum Cryptography. Then, we study vulnerabilities of a recently proposed authentication protocol intended to rule out a "man-in-the-middle" attack on Quantum Cryptography. Here, we point out that the proposed authentication primitive is not secure when used in a generic Quantum Cryptographic protocol. Lastly, we estimate the lifetime of authentication using encrypted tags when the encryption key is partially known. Under simplifying assumptions, we derive that the lifetime is linearly dependent on the length of the authentication key. Experimental results that support the theoretical results are also presented.
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| 3. |
- Berthold, Stefan, 1982-
(författare)
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Towards Inter-temporal Privacy Metrics
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Informational privacy of individuals has significantly gained importance after information technology has become widely deployed. Data, once digitalised, can be copied and distributed at negligible costs. This has dramatic consequences for individuals that leave traces in form of personal data whenever they interact with information technology. The right of individuals for informational privacy, in particular to control the flow and use of their personal data, is easily undermined by those controlling the information technology. The objective of this thesis is the measurement of informational privacy with a particular focus on scenarios where an individual discloses personal data to a second party, the data controller, which uses this data for re-identifying the individual within a set of others, the population. Several instances of this scenario are discussed in the appended papers, most notably one which adds a time dimension to the scenario for modelling the effects of the time passed between data disclosure and usage. This extended scenario leads to a new framework for inter-temporal privacy metrics. The common dilemma of all privacy metrics is their dependence on the information available to the data controller. The same information may or may not be available to the individual and, as a consequence, the individual may be misguided in his decisions due to his limited access to the data controller’s information when using privacy metrics. The goal of this thesis is thus not only the specification of new privacy metrics, but also the contribution of ideas for mitigating this dilemma. However a solution will rather be a combination of technological, economical and legal means than a purely technical solution.
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| 4. |
- Blom, Rolf, et al.
(författare)
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Data Network Security : Part I Problem Survey and Model
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Data encryption and related methods may be used to preserve information security i n a data network. Here information security is defined as the degree to which the destruction, change or loss of information is presented. Information is defined as the content of the message represented by the data. The information in a block of data is unchanged if the intended result of the transmission of the block is obtained. This means for example that the original message reaches the correct destination where it is interpreted as intended. Undisturbed information does not, in general, require un disturbed data.The network is supposed to be a public network, accessed by many different users. We are interested in a well defined group of users who are communicating mainly among themselves. Different groups, however, are also allowed to communicate in a well defined manner. The logical structure of the communication within a group is star-shaped. The information communicated within the groups hall be protected against threats from other users of the network, from illegitimate users (wiretappers etc) and from members in the group. The structure of the threats is described in section 3 of this paper.The network itself and the requirement it imposes are supposed to be unchanged. Encryption and decryption are taking place outside the network. The encrypted data shall comply with the requirements of the network. The communication process in the group consists of time-limited messages which are essentially transmitted from one point to another in the network. This is the basis for the model of the communication which is described in section 4. The model, although simple, enables us to structure the problems in connection with encryption/decryption. This is done in section 5 and 6. The purpose of the paper is to form a basis for synthesis of security measures by means on cryptological methods. The analysis is general enough to be applied to any data network and any type of user group.
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| 5. |
- Fåk, Viiveke, et al.
(författare)
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Inslag av teknik i humanistisk universitetsutbildning : Ett försök, en utredning och ett förslag
- 1981
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Sedan några år ger vi en kurs i Telekommunikationsteknikens utveckling för elever vid Kulturkommunikationslinjen vid Linköpings Universitet. Syftet med denna kurs var att ge även humaniorastuderande en grundläggande kunskap i för dem relevant teknik. Erfarenheterna av den kursen ledde oss till att. diskutera hur humanister skulle bibringas kunskap om teknik i allmänhet. Dessa diskussioner vidgades till den här rapporterade utredningen, där vi dels berättar om våra erfarenheter av den nämnda kursen, redogör för resultaten av en enkätundersökning bland eleverna som genomgått kursen och diskuterar vilka inslag av teknik som bör finnas i humanistisk universitetsutbildning och hur dessa inslag bör utformas. För den senare delen har vi också diskuterat med åtskilliga företrädare för utländska universitet, främst amerikanska, om deras erfarenhet av att undervisa i tekniska ämnen för humanister.
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| 6. |
- Fåk, Viiveke, 1948-
(författare)
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IT - Risks and Security
- 2010
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Ingår i: Risks in Technological Systems. - London : Springer-Verlag. - 9781848826403 - 9781848826410 ; , s. 143-160
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- "Risks in Technological Systems" is an interdisciplinary university textbook and a book for the educated reader on the risks of today’s society. In order to understand and analyze risks associated with the engineering systems on which modern society relies, other concerns have to be addressed, besides technical aspects. In contrast to many academic textbooks dealing with technological risks, this book has a unique interdisciplinary character that presents technological risks in their own context. Twenty-four scientists have come together to present their views on risks in technological systems. Their scientific disciplines cover not only engineering, economics and medicine, but also history, psychology, literature and philosophy. Taken together these contributions provide a broad, but accurate, interdisciplinary introduction to a field of increasing global interest, as well as rich opportunities to achieve in-depth knowledge of the subject.
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| 7. |
- Ingemarsson, Ingemar, et al.
(författare)
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Computer Security 1981
- 1976
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The goal of COMPUTER SECURITY 1981 is to prediet the demand for protection of eleetronic data processing (EDP) and for the information processed. To predict the future demands on computer security we have discussed the issue with several people involved in one way or another with EDP. These discussions, our own knowledge other background material have been the material for discussions amongst the authors. The results are divided into two parts. In the first part (section 4) we have been as objective as possible. In the latter part (section 5) we have discussed the differences between the results in section 4 and our own opinion as proffessional researchers.In addition the report covers a summary of how EDP is used 1981 and a section describing the structure of the security field (which we have used in the interviews) and an outline of the investigation.
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| 8. |
- Lundin, Reine, 1974-
(författare)
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Towards Measurable and Tunable Security
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many security services today only provides one security configuration at run-time, and cannot then utilize the trade-off between performance and security. In order to make use of this trade-off, tunable security services providing several security configurations that can be selected at run-time are needed. To be able to make intelligent choices on which security configuration to use for different situations we need to know how good they are, i.e., we need to order the different security configurations with respect to each security attribute using measures for both security and performance. However, a key issue with computer security is that it is due to its complex nature hard to measure. As the title of this thesis indicates, it discusses both security measures and tunable security services. Thus, it can be seen to consist of two parts. In the first part, discussing security measures for tunable security services, an investigation on the security implications of selective encryption by using guesswork as a security measure is made. Built on this an investigation of the relationship between guesswork and entropy. The result shows that guesswork, after a minor redefinition, is equal to the sum of the entropy and the relative entropy. The second part contributes to the area of tunable security services, e.g., services that provides several security configurations at run-time. In particular, we present the mobile Crowds (mCrowds) system, an anonymity technology for the mobile Internet developed at Karlstad University, and a tunable encryption service, that is based on a selective encryption paradigm and designed as a middleware. Finally, an investigation of the tunable features provided by Mix-Nets and Crowds are done, using a conceptual model for tunable security services.
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