Oleksandr Letychevskyi; Yaroslav Hryniuk; Viktor Yakovlev; Volodymyr Peschanenko; Viktor Radchenko
Abstract
This paper explores the algebraic matching approach for detection of vulnerabilities in binary codes. The algebraic programming system is used for implementing this method. It is anticipated that models of vulnerabilities and programs to be verified are presented as behavior algebra and ...
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This paper explores the algebraic matching approach for detection of vulnerabilities in binary codes. The algebraic programming system is used for implementing this method. It is anticipated that models of vulnerabilities and programs to be verified are presented as behavior algebra and action language specifications. The methods of algebraic matching are based on rewriting rules and techniques with usage of conditional rewriting. This process is combined with symbolic modeling that gives a possibility to provide accurate detection of vulnerabilities. The paper provides examples of formalization of vulnerability models and translation of binary codes to behavior algebra expressions.
S. Shokrollahi; F. Shams; J. Esmaeili
Abstract
The primary characteristic of an Ultra-Large-Scale (ULS) system is ultra-large size on any related dimension. A ULS system is generally considered as a system-of-systems with heterogeneous nodes and autonomous domains. As the size of a system-of-systems grows, and interoperability demand between ...
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The primary characteristic of an Ultra-Large-Scale (ULS) system is ultra-large size on any related dimension. A ULS system is generally considered as a system-of-systems with heterogeneous nodes and autonomous domains. As the size of a system-of-systems grows, and interoperability demand between sub-systems is increased, achieving more scalable and dynamic access control system becomes an important issue. The Attribute-Based Access Control (ABAC) model is a proper candidate to be used in such an access control system. The correct deployment and enforcement of ABAC policies in a ULS system requires secure and scalable collaboration among different distributed authorization components. A large number of these authorization components should be able to join different domains dynamically and communicate with each other anonymously. Dynamic configuration and reconfiguration of authorization components makes authorization system more complex to manage and maintain in a ULS system. In this paper, an access control middleware is proposed to overcome the complexity of deployment and enforcement of ABAC policies in ULS systems. The proposed middleware is data-centric and consists of two layers. The lower layer is a Data-Distribution-Service (DDS) middleware used for loosely-coupled-communication among authorization components. The upper layer is used for secure configuration and reconfiguration of authorization components. An executable model of the proposed middleware is also represented by a Colored-Petri-Net (CPN) model. This executable model is used to analyze the behavior of the proposed middleware.
A. Fanian; M. Berenjkoub; T. A. Gulliver
Abstract
The widespread use of wireless cellular networks has made security an ever increasing concern. GSM is the most popular wireless cellular standard, but security is an issue. The most critical weakness in the GSM protocol is the use of one-way entity authentication, i.e., only the mobile station is authenticated ...
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The widespread use of wireless cellular networks has made security an ever increasing concern. GSM is the most popular wireless cellular standard, but security is an issue. The most critical weakness in the GSM protocol is the use of one-way entity authentication, i.e., only the mobile station is authenticated by the network. This creates many security problems including vulnerability against man-in-the-middle attacks. Several solutions have been proposed to establish mutual entity authentication. However, none provide a aw-free bilateral authentication protocol. In this paper, we show that a recently proposed solution is vulnerable to a "type attack". Then, we propose a novel mutual entity authentication using the TESLA protocol. The proposed solution not only provides secure bilateral authentication, but also decreases the call setup time and the required connection bandwidth. An important feature of the proposed protocol is that it is compatible with the GSM standard.
V. Rijmen
Abstract
Stream ciphers are an important class of symmetric cryptographic algorithms. The eSTREAM project contributed significantly to the recent increase of activity in this field. In this paper, we present a survey of the eSTREAM project. We also review recent time/memory/data and time/memory/key trade-offs ...
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Stream ciphers are an important class of symmetric cryptographic algorithms. The eSTREAM project contributed significantly to the recent increase of activity in this field. In this paper, we present a survey of the eSTREAM project. We also review recent time/memory/data and time/memory/key trade-offs relevant for the generic attacks on stream ciphers.
M. Bishop
Abstract
Until recently, computer security was an obscure discipline that seemed to have little relevance to everyday life. With the rapid growth of the Internet, e-commerce, and the widespread use of computers, computer security touches almost all aspects of daily life and all parts of society. Even those who ...
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Until recently, computer security was an obscure discipline that seemed to have little relevance to everyday life. With the rapid growth of the Internet, e-commerce, and the widespread use of computers, computer security touches almost all aspects of daily life and all parts of society. Even those who do not use computers have information about them stored on computers. This paper reviews some aspects of the past and current state of computer security, and speculates about what the future of the field will being.
R. Hooshmand; T. Eghlidos; M. R. Aref
Abstract
This paper proposes an efficient joint secret key encryption-channel coding cryptosystem, based on regular Extended Difference Family Quasi-Cyclic Low-Density Parity-Check codes. The key length of the proposed cryptosystem decreases up to 85 percent using a new efficient compression algorithm. Cryptanalytic ...
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This paper proposes an efficient joint secret key encryption-channel coding cryptosystem, based on regular Extended Difference Family Quasi-Cyclic Low-Density Parity-Check codes. The key length of the proposed cryptosystem decreases up to 85 percent using a new efficient compression algorithm. Cryptanalytic methods show that the improved cryptosystem has a significant security advantage over Rao-Nam cryptosystem against chosen plaintext attacks, benefiting from an improvement on the structure of the Rao-Nam cryptosystem and proper choices of code parameters. Moreover, the proposed cryptosystem benefits from the highest code rate and a proper error performance.
R. Ganjavi; M. Rajabzadeh Asaar; M. Salmasizadeh
Abstract
An Optimistic Fair Exchange (OFE) protocol is a good way for two parties to exchange their digital items in a fair way such that at the end of the protocol execution, both of them receive their items or none of them receive anything. In an OFE protocol there is a semi-trusted third party, named arbitrator, ...
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An Optimistic Fair Exchange (OFE) protocol is a good way for two parties to exchange their digital items in a fair way such that at the end of the protocol execution, both of them receive their items or none of them receive anything. In an OFE protocol there is a semi-trusted third party, named arbitrator, which involves in the protocol if it is necessary. But there is a security problem when arbitrator acts dishonestly and colludes with the verifier, that is, the arbitrator can complete the transaction without getting signer's agreement. Huang et al. in 2011 addressed this issue by formalizing the accountability property. However, Huang et al.'s scheme is secure in the random oracle model which is not available in the real world. We present the first generic accountable OFE protocol that is secure in the standard model by using traceable ring signatures (TRSs) as our primitive. We prove the security of our protocol under the chosen-key model and multi-user setting.
M. Pourpouneh; R. Ramezanian
Abstract
In this paper, we shortly review two formal approaches in verification of security protocols; model checking and theorem proving. Model checking is based on studying the behavior of protocols via generating all different behaviors of a protocol and checking whether the desired goals are satisfied in ...
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In this paper, we shortly review two formal approaches in verification of security protocols; model checking and theorem proving. Model checking is based on studying the behavior of protocols via generating all different behaviors of a protocol and checking whether the desired goals are satisfied in all instances or not. We investigate Scyther operational semantics as n example of this approach and then we model and verify some famous security protocols using Scyther. Theorem proving is based on deriving the desired goals from assumption of protocols via a deduction system. We define a deduction system named Simple Logic for Authentication to formally define the notion of authenticated communication based on the structure of the messages, and then we several famous protocols using our proposed deduction system and compare it with the verification results of Scyther model checking.
P. Rastegari; M. Berenjkoub
Abstract
Certificateless public key cryptography (CL-PKC) is a useful method in order to solve the problems of traditional public key infrastructure (i.e., large amount of computation, storage and communication costs for managing certificates) and ID-based public key cryptography (i.e., key escrow problem), simultaneously. ...
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Certificateless public key cryptography (CL-PKC) is a useful method in order to solve the problems of traditional public key infrastructure (i.e., large amount of computation, storage and communication costs for managing certificates) and ID-based public key cryptography (i.e., key escrow problem), simultaneously. A signcryption scheme is an important primitive in cryptographic protocols which provides the goals of signing and encrypting, simultaneously. In 2010, Liu et al. presented the first certificateless signcryption (CLSC) scheme in the standard model, but their scheme is vulnerable against different attacks presented in the literature, till now. In this paper, we improve their scheme and propose a new CLSC scheme, which is semantically secure against adaptive chosen ciphertext attack under the (Ѕ2, 5)-BDHE-Set assumption and existentially unforgeable against adaptive chosen message attack under the 3-CDHE assumption in the standard model. Our scheme is more efficient than all other secure CLSC schemes in the standard model proposed up to now.
A. Rezaei Shahmirzdi; A. Azimi; M. Salmasizadeh; J. Mohajeri; M. R. Aref
Abstract
Impossible differential attack is a well-known mean to examine robustness of block ciphers. Using impossible differential cryptanalysis, we analyze security of a family of lightweight block ciphers, named Midori, that are designed considering low energy consumption. Midori state size can be ...
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Impossible differential attack is a well-known mean to examine robustness of block ciphers. Using impossible differential cryptanalysis, we analyze security of a family of lightweight block ciphers, named Midori, that are designed considering low energy consumption. Midori state size can be either 64 bits for Midori64 or 128 bits for Midori128; however, both versions have key size equal to 128 bits. In this paper, we mainly study security of Midori64. To this end, we use various techniques such as early-abort, memory reallocation, miss-in-the-middle and turning to account the inadequate key schedule algorithm of Midori64. We first show two new 7round impossible differential characteristics which are, to the best of our knowledge, the longest impossible differential characteristics found for Midori64. Based on the new characteristics, we mount three impossible differential attacks for 10, 11, and 12 rounds on Midori64 with 2 87.7 , 2 90.63 , and 2 90.51 time complexity, respectively, to retrieve the master-key.
Simin Ghasemi; Mohammad Ali Hadavi; Mina Niknafs
Abstract
Correctness verification of query results is a significant challenge in database outsourcing. Most of the proposed approaches impose high overhead, which makes them impractical in real scenarios. Probabilistic approaches are proposed in order to reduce the computation overhead pertaining to the verification ...
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Correctness verification of query results is a significant challenge in database outsourcing. Most of the proposed approaches impose high overhead, which makes them impractical in real scenarios. Probabilistic approaches are proposed in order to reduce the computation overhead pertaining to the verification process. In this paper, we use the notion of trust as the basis of our probabilistic approach to efficiently verify the correctness of query results. The trust is computed based on observing the history of interactions between clients and the service provider. Our approach exploits Merkle Hash Tree as an authentication data structure. The amount of trust value towards the service provider leads to investigating just an appropriate portion of the tree. Implementation results of our approach show that considering the trust, derived from the history of interactions, provides a trade-off between performance and security, and reduces the imposed overhead for both clients and the service provider in database outsourcing scenario.
M. A. Akhaee; F. Marvasti
Abstract
This paper investigates digital data hiding schemes. The concept of information hiding will be explained at first, and its traits, requirements, and applications will be described subsequently. In order to design a digital data hiding system, one should first become familiar with the concepts and criteria ...
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This paper investigates digital data hiding schemes. The concept of information hiding will be explained at first, and its traits, requirements, and applications will be described subsequently. In order to design a digital data hiding system, one should first become familiar with the concepts and criteria of information hiding. Having knowledge about the host signal, which may be audio, image, or video and the final receiver, which is Human Auditory System (HAS) or Human Visual System (HVS), is also beneficial. For the speech/audio case, HAS will be briefly reviewed to find out how to make the most of its weaknesses for embedding as much data as possible. The same discussion also holds for the image watermarking. Although several audio and image data hiding schemes have been proposed so far, they can be divided into a few categories. Hence, conventional schemes along with their recently published extensions are introduced. Besides, a general comparison is made among these methods leading researchers/designers to choose the appropriate schemes based on their applications. Regarding the old scenario of the prisoner-warden and the evil intention of the warden to eavesdrop and/or destroy the data that Alice sends to Bob, there are both intentional and unintentional attacks to digital information hiding systems, which have the same effect based on our definition. These attacks can also be considered for testing the performance or benchmarking, of the watermarking algorithm. They are also known as steganalysis methods which will be discussed at the end of the paper.
Majid Mahmoudzadeh Niknam; Sadegh Sadeghi; Mohammad Reza Aref; Nasour Bagheri
Abstract
In this paper, we present some attacks on GAGE, InGAGE, and CiliPadi which are candidates of the first round of the NIST-LWC competition. GAGE and InGAGE are lightweight sponge based hash function and Authenticated Encryption with Associated Data (AEAD), respectively and support different sets of parameters. ...
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In this paper, we present some attacks on GAGE, InGAGE, and CiliPadi which are candidates of the first round of the NIST-LWC competition. GAGE and InGAGE are lightweight sponge based hash function and Authenticated Encryption with Associated Data (AEAD), respectively and support different sets of parameters. The length of hash, key, and tag are always 256, 128, and 128 bits, respectively. We show that the security bounds for some variants of its hash and AEAD are less than the designers' claims. For example, the designers' security claim of preimage attack for a hash function when the rate is 128 bits and the capacity is $256$ bits, is 2^{256}, however, we show that the security of preimage for this parameter set is 2^{128}. Also, the designer claimed security of confidentiality for an AEAD, when the rate is 8 bits and the capacity is 224 bits, is 2^{116}, however, we show the security of confidentiality for it is 2^{112$. We also investigate the structure of the permutation used in InGAGE and present an attack to recover the key for reduced rounds of a variant of InGAGE. In an instance of AEAD of InGAGE, when the rate is 8 bits and the capacity is 224 bits, we recover the key when the number of the composition of the main permutation with itself, i.e., r_{1}, is less than 8. We also show that CiliPadi is vulnerable to the length extension attack by presenting concrete examples of forged messages.
F. Salim; J. Reid; E. Dawson
Abstract
This article presents a survey of authorization models and considers their 'fitness-for-purpose' in facilitating information sharing. Network-supported information sharing is an important technical capability that underpins collaboration in support of dynamic and unpredictable activities such as emergency ...
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This article presents a survey of authorization models and considers their 'fitness-for-purpose' in facilitating information sharing. Network-supported information sharing is an important technical capability that underpins collaboration in support of dynamic and unpredictable activities such as emergency response, national security, infrastructure protection, supply chain integration and emerging business models based on the concept of a 'virtual organization'. The article argues that present authorization models are inflexible and poorly scalable in such dynamic environments due to their assumption that the future needs of the system can be predicted, which in turn justifies the use of persistent authorization policies. The article outlines the motivation and requirement for a new flexible authorization model that addresses the needs of information sharing. It proposes that a flexible and scalable authorization model must allow an explicit specification of the objectives of the system and access decisions must be made based on a late trade-off analysis between these explicit objectives. A research agenda for the proposed Objective-Based Access Control concept is presented.
P. Rogaway
Abstract
This paper mirrors an invited talk to ISCISC 2011. It is not a conventional paper so much as an essay summarizing thoughts on a little-talked-about subject. My goal is to intermix some introspection about definitions with examples of them, these examples drawn mostly from cryptography. Underpinning our ...
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This paper mirrors an invited talk to ISCISC 2011. It is not a conventional paper so much as an essay summarizing thoughts on a little-talked-about subject. My goal is to intermix some introspection about definitions with examples of them, these examples drawn mostly from cryptography. Underpinning our discussion are two themes. The first is that definitions are constructed. They are invented by man, not unearthed from the maws of scientific reality. The second theme is that definitions matter. They have been instrumental in changing the character of modern cryptography, and, I suspect, have the potential to change the character of other fields as well.
J. Dj. Golic'
Abstract
A unified method for statistical anomaly detection in intrusion detection systems is theoretically introduced. It is based on estimating a dispersion measure of numerical or symbolic data on successive moving windows in time and finding the times when a relative change of the dispersion measure is significant. ...
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A unified method for statistical anomaly detection in intrusion detection systems is theoretically introduced. It is based on estimating a dispersion measure of numerical or symbolic data on successive moving windows in time and finding the times when a relative change of the dispersion measure is significant. Appropriate dispersion measures, relative differences, moving windows, as well as techniques for their efficient estimation are proposed. In particular, the method can be used for detecting network traffic anomalies due to network failures and network attacks such as (distributed) denial of service attacks, scanning attacks, SPAM and SPIT attacks, and massive malicious software attacks.
M. Behniafar; A.R. Nowroozi; H.R. Shahriari
Abstract
Internet of Things is an ever-growing network of heterogeneous and constraint nodes which are connected to each other and the Internet. Security plays an important role in such networks. Experience has proved that encryption and authentication are not enough for the security of networks and an Intrusion ...
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Internet of Things is an ever-growing network of heterogeneous and constraint nodes which are connected to each other and the Internet. Security plays an important role in such networks. Experience has proved that encryption and authentication are not enough for the security of networks and an Intrusion Detection System is required to detect and to prevent attacks from malicious nodes. In this regard, Anomaly based Intrusion Detection Systems identify anomalous behavior of the network and consequently detect possible intrusion, unknown and stealth attacks. To this end, this paper analyses, evaluates and classifies anomaly detection approaches and systems specific to the Internet of Things. For this purpose, anomaly detection systems and approaches are analyzed in terms of engine architecture, application position, and detection method and in each point of view, approaches are investigated considering the associated classification.
Milad Seddigh; Hadi Soleimany
Abstract
In cloud computing, multiple users can share the same physical machine that can potentially leak secret information, in particular when the memory de-duplication is enabled. Flush+Reload attack is a cache-based attack that makes use of resource sharing. T-table implementation of AES is commonly used ...
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In cloud computing, multiple users can share the same physical machine that can potentially leak secret information, in particular when the memory de-duplication is enabled. Flush+Reload attack is a cache-based attack that makes use of resource sharing. T-table implementation of AES is commonly used in the crypto libraries like OpenSSL. Several Flush+Reload attacks on T-table implementation of AES have been proposed in the literature which requires a notable number of encryptions. In this paper, we present a technique to enhance the Flush+Reload attack on AES in the ciphertext-only scenario by significantly reducing the number of needed encryptions in both native and cross-VM setups. In this paper, we focus on finding the wrong key candidates and keep the right key by considering only the cache miss event. Our attack is faster than previous Flush+Reload attacks. In particular, our method can speed-up the Flush+Reload attack in cross-VM environment significantly. To verify the theoretical model, we implemented the proposed attack.
S. Mashhadi
Abstract
A multi-secret sharing scheme (MSS) allows a dealer to share multiple secrets among a set of participants. in such a way a multi-secret sharing scheme (MSS) allows a dealer to share multiple secrets among a set of participants, such that any authorized subset of participants can reconstruct the secrets. ...
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A multi-secret sharing scheme (MSS) allows a dealer to share multiple secrets among a set of participants. in such a way a multi-secret sharing scheme (MSS) allows a dealer to share multiple secrets among a set of participants, such that any authorized subset of participants can reconstruct the secrets. Up to now, existing MSSs either require too long shares for participants to be perfect secure, or do not have a formal security analysis/proof. In 2013, Herranz et al. provided the first formal definition of computational security for multi-stage secret sharing scheme (MSSS) in the standard model and proposed a practical and secure scheme. As far as we know, their scheme is the only computationally secure MSS in the standard model, and there is no formal definition of the computational security for other categories of MSSs. Based on this motivation, in this paper, we define the first formal model of indistinguishability against the chosen secret attacks (CSA) for other types of MSSs in the standard model. Furthermore, we present two practical CSA-secure MSSs, belonging to different types of MSSs and enjoying the advantage of short shares. They are also provably secure in the standard model. Based on the semantic security of the underlying encryption schemes, we prove the security of our schemes.
Sh. Zamanzadeh; A. Jahanian
Abstract
Fab-less business model in semiconductor industry has led to serious concerns about trustworthy hardware. In untrusted foundries and manufacturing companies, submitted layout may be analyzed and reverse engineered to steal the information of a design or insert malicious Trojans. Understanding the netlist ...
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Fab-less business model in semiconductor industry has led to serious concerns about trustworthy hardware. In untrusted foundries and manufacturing companies, submitted layout may be analyzed and reverse engineered to steal the information of a design or insert malicious Trojans. Understanding the netlist topology is the ultimate goal of the reverse engineering process. In this paper, we propose a netlist encryption mechanism to hide the interconnect topology inside an IC. Moreover, new special standard cells (Wire Scrambling cells) are designed to play the role of netlist encryption. Furthermore, a design ow is proposed to insert the WS-cells inside the netlist with the aim of maximum obfuscation and minimum overhead. It is worth noting that this mechanism is fully automated with no need to detail information of the functionality and structure of the design. Our proposed mechanism is implemented in an academic physical design framework (EduCAD). Experimental results show that reverse engineering can be hindered considerably in cost of negligible overheads by 23% in area, 3.25% in delay and 14.5% in total wire length. Reverse engineering is evaluated by brute-force attack, and the learned information is 0% and the Hamming distance is approximately 50%.
Seyed Alireza Hasheminasab; Behrouz Tork Ladani; Tansu Alpcan
Abstract
In today's highly interconnected networks, security of the entities are often interdependent. This means security decisions of the agents are not only influenced by their own costs and constraints, but also are affected by their neighbors’ decisions. Game theory provides a rich set of tools to ...
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In today's highly interconnected networks, security of the entities are often interdependent. This means security decisions of the agents are not only influenced by their own costs and constraints, but also are affected by their neighbors’ decisions. Game theory provides a rich set of tools to analyze such influence networks. In the game model, players try to maximize their utilities through security investments considering the network structure, costs and constraints, which have been set by the network owner. However, decisions of selfish entities to maximize their utilities do not always lead to a socially optimum solution. Therefore, motivating players to reach the social optimum is of high value from the network owner’s point of view. The network owner wants to maximize the overall network security by designing the game's parameters. As far as we know, there is no notable work in the context of linear influence networks to introduce appropriate game design for this purpose. This paper presents design methods that make use of the adjustments of players’ costs, interdependencies, and constraints to align players' incentives with a network-wide global objective. We present a comprehensive investigation of existence and uniqueness conditions of Nash Equilibrium in such environments. Furthermore, numerical results of applying the proposed mechanisms in a sample real-world example are illustrated.
F. Farhat; A. Diyanat; Sh. Ghaemmaghami; M. R. Aref
Abstract
So far, various components of image characteristics have been used for steganalysis, including the histogram characteristic function, adjacent colors distribution, and sample pair analysis. However, some certain steganography methods have been proposed that can thwart some analysis approaches through ...
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So far, various components of image characteristics have been used for steganalysis, including the histogram characteristic function, adjacent colors distribution, and sample pair analysis. However, some certain steganography methods have been proposed that can thwart some analysis approaches through managing the embedding patterns. In this regard, the present paper is intended to introduce a new analytical method for detecting stego images, which is robust against some of the embedding patterns designed specifically to foil steganalysis attempts. The proposed approach is based on the analysis of the eigenvalues of the cover correlation matrix used for the purpose of the study. Image cloud partitioning, vertical correlation function computation, constellation of the correlated data, and eigenvalues examination are the major challenging stages of this analysis method. The proposed method uses the LSB plane of images in spatial domain, extendable to transform domain, to detect low embedding rates-a major concern in the area of the LSB steganography. The simulation results based on deviation detection and rate estimation methods indicated that the proposed approach outperforms some well-known LSB steganalysis methods, specifically at low embedding rates.
E. Damiani; S. Cimato; G. Gianini
Abstract
Traditionally, risk assessment consists of evaluating the probability of "feared events", corresponding to known threats and attacks, as well as these events' severity, corresponding to their impact on one or more stakeholders. Assessing risks of cloud-based processes is particularly difficult due to ...
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Traditionally, risk assessment consists of evaluating the probability of "feared events", corresponding to known threats and attacks, as well as these events' severity, corresponding to their impact on one or more stakeholders. Assessing risks of cloud-based processes is particularly difficult due to lack of historical data on attacks, which has prevented frequency-based identification of "typical" threats and attack vectors. Also, the dynamic, multi-party nature of cloud-based processes makes severity assessment very dependent on the particular set of stakeholders involved in each process execution. In this paper, we tackle these problems by presenting a novel, process-oriented quantitative risk assessment methodology aimed at disclosure risks on cloud computing platforms. Key advantages of our methodology include (i) a fully quantitative and iterative approach, which enables stakeholders to compare alternative versions of cloud-based processes (e.g., with and without security controls) (ii) non-frequency-based probability estimates, which allow analyzing threats for which a detailed history is not available (iii) support for quick visual comparisons of risk profiles of alternative processes even when impact cannot be exactly quantified.
Sh. Khazaei; F. Moazami
Abstract
Guess-and-determine attack is one of the general attacks on stream ciphers. It is a common cryptanalysis tool for evaluating security of stream ciphers. The effectiveness of this attack is based on the number of unknown bits which will be guessed by the attacker to break the cryptosystem. In this work, ...
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Guess-and-determine attack is one of the general attacks on stream ciphers. It is a common cryptanalysis tool for evaluating security of stream ciphers. The effectiveness of this attack is based on the number of unknown bits which will be guessed by the attacker to break the cryptosystem. In this work, we present a relation between the minimum numbers of the guessed bits and uniquely restricted matching of a graph. This leads us to see that finding the minimum number of the guessed bits is NP-complete. Although fixed parameter tractability of the problem in term of minimum number of the guessed bits remains an open question, we provide some related results. Moreover, we introduce some closely related graph concepts and problems including alternating cycle free matching, jump number and forcing number of a perfect matching.
A. Javadi; M. Amini
Abstract
Access control in open and dynamic Pervasive Computing Environments (PCEs) is a very complex mechanism and encompasses various new requirements. In fact, in such environments, context information should be used in access control decision process; however, it is not applicable to gather all context information ...
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Access control in open and dynamic Pervasive Computing Environments (PCEs) is a very complex mechanism and encompasses various new requirements. In fact, in such environments, context information should be used in access control decision process; however, it is not applicable to gather all context information completely and accurately all the time. Thus, a suitable access control model for PCEs not only should be context-aware, but also must be able to deal with imperfect context information. In addition, due to the diversity and heterogeneity of resources and users and their security requirements in PCEs, supporting exception and default policies is a necessary requirement. In this paper, we propose a Semantic-Aware Role-Based Access Control (SARBAC) model satisfying the aforementioned requirements using MKNF+. The main contribution of our work is defining an ontology for context information along with using MKNF+ rules to define context-aware role activation and permission assignment policies. Dividing role activation and permission assignment policies into three layers and using abstract and concrete predicates not only make security policy specification more flexible and manageable, but also make definition of exception and default polices possible. The expressive power of the proposed model is demonstrated through a case study in this paper.