| 1. |
- Arndt, D. S., et al.
(författare)
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STATE OF THE CLIMATE IN 2017
- 2018
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 99:8, s. S1-S310
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Forskningsöversikt (refereegranskat)
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| 2. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Afanassiev, Valentin, et al.
(författare)
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Fast authentication codes based on random polynomial residue classes
- 1997
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Ingår i: Proceedings 1997 IEEE International Symposium on Information Theory. - 2157-8095. - 0780339568 - 9780780339569 ; , s. 175-175
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Konferensbidrag (refereegranskat)abstract
- The verification of the authenticity of a text document or a datafile is one of the main applications of cryptographic techniques. A common used technique for this purpose is the application of a message authentication code (MAC). Usually the MAC computation has to be done in software. Based on the relationship between error-correcting codes and so-called families of almost universal hash functions, and the error-correcting codes using polynomial residue classes we describe an efficient procedure for a MAC computation which is much faster than the standard MAC constructions using MD5 or SHA and uses much less key bits than the fast MACs based on bucket hashing.
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| 4. |
- Afanassiev, Valentine, et al.
(författare)
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Fast message authentication using efficient polynomial evaluation
- 1997
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Ingår i: Fast Software Encryption : 4th International Workshop, FSE 1997, Proceedings - 4th International Workshop, FSE 1997, Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 3540632476 - 9783540632474 ; 1267, s. 190-204
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Konferensbidrag (refereegranskat)abstract
- Message authentication codes (MACs) using polynomial evaluation have the advantage of requiring a very short key even for very large messages. We describe a low complexity software polynomial evaluation procedure, that for large message sizes gives a MAC that has about the same low software complexity as for bucket hashing but requires only small keys and has better security characteristics.
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| 5. |
- Alfredsson, Lars-Inge, 1964-
(författare)
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VLSI Architectures and Arithmetic Operations with Application to the Fermat Number Transform
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The properties of arithmetic operations in Fermat integer quotient rings 2m+1, where m = 2t, are investigated. The arithmetic operations considered are mainly those involved in the computation of the Fermat number transform. We consider some ways of representing the binary coded integers in such rings and investigate VLSI architectures for arithmetic operations, with respect to the different element representations. The VLSI architectures are mutually compared with respect to area (A) and time (T) complexity and area-time performance (AT2). The VLSI model chosen is a linears witch-level RC model.In the polar representation, the nonzero elements of a field are represented by the powers of a primitive element of the field. In the thesis we particularly investigate the properties of arithmetic operations and their corresponding VLSI architectureswith respect to the polar representation of the elements of Fermat prime fields. Somenew results regarding the applicability of the Fermat number transform when usingthe polar representation are also presented.
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| 6. |
- Anderson, Kristin, 1977-
(författare)
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Tree Structures in Broadcast Encryption
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need for broadcast encryption arises when a sender wishes to securely distribute messages to varying subsets of receivers, using a broadcast channel, for instance in a pay-TV scenario. This is done by selecting subsets of users and giving all users in the same subset a common decryption key. The subsets will in general be overlapping so that each user belongs to many subsets and has several different decryption keys. When the sender wants to send a message to some users, the message is encrypted using keys that those users have. In this thesis we describe some broadcast encryption schemes that have been proposed in the literature. We focus on stateless schemes which do not require receivers to update their decryption keys after the initial keys have been received; particularly we concentrate on the Subset Difference (SD) scheme.We consider the effects that the logical placement of the receivers in the tree structure used by the SD scheme has on the number of required transmissions for each message. Bounds for the number of required transmissions are derived based on the adjacency of receivers in the tree structure. The tree structure itself is also studied, also resulting in bounds on the number of required transmissions based on the placement of the users in the tree structure.By allowing a slight discrepancy between the set of receivers that the sender intends to send to and the set of receivers that actually can decrypt the message, we can reduce the cost in number of transmissions per message. We use the concept of distortion to quantify the discrepancy and develop three simple algorithms to illustrate how the cost and distortion are related.
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| 7. |
- Aslam, Mudassar, 1979-
(författare)
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Secure Service Provisioning in a Public Cloud
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolution of cloud technologies which allows the provisioning of IT resources over the Internet promises many benefits for the individuals and enterprises alike. However, this new resource provisioning model comes with the security challenges which did not exist in the traditional resource procurement mechanisms. We focus on the possible security concerns of a cloud user (e.g. an organization, government department, etc.) to lease cloud services such as resources in the form of Virtual Machines (VM) from a public Infrastructure-as-a-Service (IaaS) provider. There are many security critical areas in the cloud systems, such as data confidentiality, resource integrity, service compliance, security audits etc. In this thesis, we focus on the security aspects which result in the trust deficit among the cloud stakeholders and hence hinder a security sensitive user to benefit from the opportunities offered by the cloud computing. Based upon our findings from the security requirements analysis,we propose solutions that enable user trust in the public IaaS clouds. Our solutions mainly deal with the secure life cycle management of the user VM which include mechanisms for VM launch and migration. The VM launch and migration solutions ensure that the user VM is always protected in the cloud by only allowing it to run on the user trusted platforms. This is done by using trusted computing techniques that allow the users to remotely attest and hence rate the cloud platforms trusted or untrusted. We also provide a prototype implementation to prove the implementation feasibility of the proposed trust enabling principles used in the VM launch and migration solutions.
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| 8. |
- Bergström, Daniel, et al.
(författare)
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Facilitating online trust with Blockchains
- 2019
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Ingår i: Ericsson Review (English Edition). - 0014-0171. ; 100:2, s. 8-17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Bierbrauer, J., et al.
(författare)
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On the construction of universal families of hash functions via geometric codes and concatenation
- 1993
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Ingår i: Advances in Cryptology / Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 9783540577669 ; 773, s. 331-342
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Konferensbidrag (refereegranskat)abstract
- In this paper we use coding theory to give simple explanations of some recent results on universal hashing. We first apply our approach to give a precise and elegant analysis of the Wegman-Carter construction for authentication codes. Using Reed-Solomon codes and the well known concept of concatenated codes we can then give some new constructions, which require much less key size than previously known constructions. The relation to coding theory allows the use of codes from algebraic curves for the construction of hash functions. Particularly, we show how codes derived from Artin-Schreier curves, Hermitian curves and Suzuki curves yield good classes of universal hash functions.
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| 10. |
- Chepyshov, V., et al.
(författare)
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A simple algorithm for fast correlation attacks on stream ciphers
- 2000
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Ingår i: Fast Software Encryption / Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540417286 ; 1978, s. 181-195
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Konferensbidrag (refereegranskat)abstract
- A new simple algorithm for fast correlation attacks on stream ciphers is presented. The advantages of the new approach are at least two. Firstly, the new algorithm significantly reduces the memory requirements compared with some recent proposals [2],[3]. This allows more powerful attacks than previously. Secondly, the simplicity of the algorithm allows us to derive theoretical results. We determine the relation between the number of observed symbols, the correlation probability, and the allowed computational complexity, required for a successful attack. Hence, we can get theoretical estimates on the required computational complexity in cases when simulation is not possible.
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| 11. |
- Chepyshov, V.V, et al.
(författare)
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The free distance of fixed convolutional rate 2/4 codes meets the Costello bound
- 1992
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Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 38:4, s. 1360-1366
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Tidskriftsartikel (refereegranskat)abstract
- The long standing question whether the free distance of fixed rate convolutional codes is as good as the Costello bound was almost solved by K.S. Zigangirov and J.L. Massey (1987). They proved that this is indeed the case for codes with long branch length and rates 2/c, c>or=5. It is shown that there exist fixed convolutional codes of rate 2/4 whose free distance d/sub free/ meets the Costello bound originally derived for time varying convolutional codes
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| 12. |
- Chepyzhov, Vladimir, et al.
(författare)
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A coding theoretic approach to attack certain stream ciphers
- 1994
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Ingår i: Proceedings - 1994 IEEE International Symposium on Information Theory, ISIT 1994. - 2157-8095. - 0780320158 - 9780780320154 ; , s. 367-367
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Konferensbidrag (refereegranskat)abstract
- We present a coding theoretic approach to the problem the initial state recovery of a linear feedback shift register when a noisy output sequence is given. Our work is focused on the investigation of the asymptotical behaviour of the recovery process. We give two algorithms which will work for shift registers with arbitrary feedback polynomial. Furthermore, the number of required given noisy symbols is close to its lower limit.
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| 13. |
- Chepyzhov, Vladimir, et al.
(författare)
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On a fast correlation attack on certain streaxn ciphers
- 1991
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Ingår i: Advances in Cryptology—EUROCRYPT 1991 : Workshop on the Theory and Application of Cryptographic Techniques, Proceedings - Workshop on the Theory and Application of Cryptographic Techniques, Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540464167 - 9783540546207 ; 547 LNCS, s. 176-185
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a new algorithm for the recovery of the initial state of a linear feedback shift register when a noisy output sequence is given. Our work is focussed on the investigation of the asymptotical behaviour of the recovery process rather than on the construction of an optimal recovery procedure. Our results show the importance of low-weight checks and show also that the complexity of the recovery problem grows less than exponentially with the length of the shift register, even if the number of taps grows linearly with the register length. Our procedure works for shift register with arbitrary feedback polynomial.
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| 14. |
- Dubrova, Elena, et al.
(författare)
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Keyed Logic BIST for Trojan Detection in SoC
- 2014
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Ingår i: <em>Proceedings of IEEE International Symposium on System-on-Chip (SOC'2014)</em>. - : IEEE conference proceedings. - 9781479968909
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Konferensbidrag (refereegranskat)abstract
- As demonstrated by the recent attack on Intel’s Ivy Bridge processor, the traditional Logic Built-In Self-Test (LBIST) methods do not provide adequate protection of SoC against malicious modifications known as hardware Trojans. In this paper, we introduce a simple but efficient countermeasure against hardware Trojans which exploits non-zero aliasing probability of LBIST. We propose to generate LBIST test patterns based on a configurable key which is decided and programed into the circuit after the manufacturing stage. Since the key and hence expected LBIST signature are unknown at the manufacturing stage, an attack based on selecting suitable values for the Trojan which result in the same signature as a fault-free circuit signature becomes infeasible.
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| 15. |
- Dubrova, Elena, et al.
(författare)
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Two Countermeasures Against Hardware Trojans Exploiting Non-Zero Aliasing Probability of BIST
- 2016
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Ingår i: Journal of Signal Processing Systems. - : Springer Science+Business Media B.V.. - 1939-8018 .- 1939-8115.
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Tidskriftsartikel (refereegranskat)abstract
- The threat of hardware Trojans has been widely recognized by academia, industry, and government agencies. A Trojan can compromise security of a system in spite of cryptographic protection. The damage caused by a Trojan may not be limited to a business or reputation, but could have a severe impact on public safety, national economy, or national security. An extremely stealthy way of implementing hardware Trojans has been presented by Becker et al. at CHES’2012. Their work have shown that it is possible to inject a Trojan in a random number generator compliant with FIPS 140-2 and NIST SP800-90 standards by exploiting non-zero aliasing probability of Logic Built-In-Self-Test (LBIST). In this paper, we present two methods for modifying LBIST to prevent such an attack. The first method makes test patterns dependent on a configurable key which is programed into a chip after the manufacturing stage. The second method uses a remote test management system which can execute LBIST using a different set of test patterns at each test cycle.
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| 16. |
- Ekdahl, Patrik, et al.
(författare)
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Incremental authentication of tree-structured documents
- 1999
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Ingår i: Information and Communication Security : 2nd International Conference, ICICS 1999, Proceedings - 2nd International Conference, ICICS 1999, Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 3540666826 - 9783540666820 - 9783540479420 ; 1726, s. 275-283
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Konferensbidrag (refereegranskat)abstract
- A new message authentication code (MAC) is described that exploits the tree structure present in many modern document formats, e.g. SGML and XML. The new code supports incremental updating of the cryptographic checksum in the process of making incremental changes to the document. Theoretical bounds on the probability of a successful substitution attack are derived. Through experimental results we demonstrate that for randomly chosen messages the success probability of such an attack will be smaller and is easily identified.
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| 17. |
- Ekstrand, Nicklas, et al.
(författare)
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Some notes on the context mapping function in lossless data compression
- 2000
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Ingår i: ; , s. 553-553
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Konferensbidrag (refereegranskat)abstract
- One of the major challenges when applying (serial) universal source coding to 2-dimensional data, e.g., images, is to determine suitable context data. For this reason the concept of Context Mapping Function (CMF) has been introduced. In this paper we discuss the foundation for CMFs as well an off-line construction method via a combinatorial optimization method.
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| 18. |
- Ekstrand, Nicklas, et al.
(författare)
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Weighting of double exponential distributed data in lossless image compression
- 1998
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Ingår i: Proceedings DCC '98 Data Compression Conference. - 0818684062
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Konferensbidrag (refereegranskat)abstract
- A probability assignment technique for weighting-based double exponential data in lossless image compression is introduced. It is shown that this technique has a favorable effect on compression when compared with traditional estimation techniques.
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| 19. |
- Hell, Martin, et al.
(författare)
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Using TPM Secure Storage in Trusted High Availability Systems
- 2014
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Ingår i: Trusted Systems/Lecture Notes in Computer Science. - Cham : Springer International Publishing. - 0302-9743. - 9783319279978 - 9783319279985 ; 9473, s. 243-258
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of providing trusted computing functionality in high availability systems. We consider the case where data is required to be encrypted with a TPM protected key. For redundancy, and to facilitate high availability, the same TPM key is stored in multiple computational units, each one ready to take over if the main unit breaks down. This requires the TPM key to be migratable. We show how such systems can be realized using the secure storage of the TPM. Hundreds of millions TPM 1.2 chips have been shipped but with the recent introduction of TPM 2.0, more manufacturers are expected to start shipping this newer TPM. Thus, a migration from TPM 1.2 to TPM 2.0 will likely be seen in the next few years. To address this issue, we also provide an API that allows a smooth upgrade from TPM 1.2 to TPM 2.0 without having to redesign the communication protocol involving the dierent entities. The API has been implemented for both TPM 1.2 and TPM 2.0.
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| 20. |
- Johansson, Thomas, et al.
(författare)
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On A2-codes including arbiter's attacks
- 1995
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Ingår i: Advances in Cryptology / Lecture Notes in Computer Science. - 1611-3349 .- 0302-9743. - 9783540601760 ; 950, s. 456-461
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Konferensbidrag (refereegranskat)abstract
- We comment on the work by R. Taylor presented at Euro-Crypt'94 (see this proceedings). We first extend some known results on authentication codes with arbitration to the case when protection against arbiter's attacks is provided. We give lower bounds on the secret key size for each participant and give a construction showing that these bounds are tight. These results improve upon previously known work and show that a claim in the aforementioned paper is wrong. This work
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| 21. |
- Johansson, Thomas, et al.
(författare)
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On the cardinality of systematic authentication codes via error-correcting codes
- 1996
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Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 42:2, s. 566-578
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Tidskriftsartikel (refereegranskat)abstract
- In both open and private communication the participants face potential threats from a malicious enemy who has access to the communication channel and can insert messages (impersonation attack) or alter already transmitted messages (substitution attack). Authentication codes (A-codes) have been developed to provide protection against these threats. In this paper we introduce a new distance, called the authentication distance (A-distance), and show that an A-code can be described as a code for the A-distance. The A-distance is directly related to the probability PS of success in a substitution attack. We show how to transform an error-correcting code into an A-code and vice versa. We further use these transformations to provide both upper and lower bounds on the size of the information to be authenticated, and study their asymptotic behavior. As examples of obtained results, we prove that the cardinality of the source state space grows exponentially with the number of keys provided PS>PI, we generalize the square-root bound given by Gilbert, MacWilliams, and Sloane in 1979, and we provide very efficient constructions using concatenated Reed-Solomon codes.
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| 22. |
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| 23. |
- Jost, Christine, et al.
(författare)
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Cryptography in an all encrypted world
- 2016
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Ingår i: Ericsson Review. - 0014-0171. ; 93:1, s. 8-19
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Tidskriftsartikel (refereegranskat)abstract
- Ensuring that communication is secure, including the ability to encrypt sensitive traffic, has always been a fundamental pillar of the telecom industry. Users expect their right to privacy to be respected, and operators expect to be able to protect themselves and their customers from various kinds of attacks. But the world is changing. Encryption technologies are advancing, regulations are changing, criminals are becoming highly tech savvy, and security awareness has become a popular conversation topic. So, in light of new threats and security demands, security protocols need a shake-up.
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| 24. |
- Jämthagen, Christopher, et al.
(författare)
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A Technique for Remote Detection of Certain Virtual Machine Monitors
- 2011
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Ingår i: Trusted Systems : Third International Conference, INTRUST 2011, Beijing, China, November 27-29, 2011, Revised Selected Papers - Third International Conference, INTRUST 2011, Beijing, China, November 27-29, 2011, Revised Selected Papers. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783642322976 - 9783642322983 ; 7222, s. 129-137
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Bokkapitel (refereegranskat)abstract
- The ability to detect a virtualized environment has both malicious and non-malicious uses. This paper reveals a new exploit and technique that can be used to remotely detect VMware Workstation, VMware Player and VirtualBox. The detection based on this technique can be done completely passively in that there is no need to have access to the remote machine and no network connections are initiated by the verifier. Using only information in the IP packet together with information sent in the user-agent string in an HTTP request, it is shown how to detect that the traffic originates from a guest in VMware Workstation, VMware Player or VirtualBox client. The limitation is that NAT has to be turned on and that the host and guest need to run different operating system families, e.g., Windows/Linux.
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| 25. |
- Kapoor, Pooja Middha, et al.
(författare)
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Combined associations of a polygenic risk score and classical risk factors with breast cancer risk
- 2021
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press (OUP). - 0027-8874 .- 1460-2105. ; 113:3, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- We evaluated the joint associations between a new 313-variant PRS (PRS313) and questionnaire-based breast cancer risk factors for women of European ancestry, using 72 284 cases and 80 354 controls from the Breast Cancer Association Consortium. Interactions were evaluated using standard logistic regression and a newly developed case-only method for breast cancer risk overall and by estrogen receptor status. After accounting for multiple testing, we did not find evidence that per-standard deviation PRS313 odds ratio differed across strata defined by individual risk factors. Goodness-of-fit tests did not reject the assumption of a multiplicative model between PRS313 and each risk factor. Variation in projected absolute lifetime risk of breast cancer associated with classical risk factors was greater for women with higher genetic risk (PRS313 and family history) and, on average, 17.5% higher in the highest vs lowest deciles of genetic risk. These findings have implications for risk prevention for women at increased risk of breast cancer.
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