J. H. Jafarian; M. Amini
Abstract
Mandatory access control models have traditionally been employed as a robust security mechanism in multilevel security environments such as military domains. In traditional mandatory models, the security classes associated with entities are context-insensitive. However, context-sensitivity of security ...
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Mandatory access control models have traditionally been employed as a robust security mechanism in multilevel security environments such as military domains. In traditional mandatory models, the security classes associated with entities are context-insensitive. However, context-sensitivity of security classes and flexibility of access control mechanisms may be required especially in pervasive computing environments. To this aim, we propose a context-aware mandatory access control model (CAMAC) capable of dynamic adaptation of access control policies to context, and of handling context-sensitive class association, in addition to preservation of confidentiality and integrity as specified in traditional mandatory access control models. In order to prevent any ambiguity, a formal specification of the model and its elements such as context predicates, context types, level update rules, and operations is required. High expressiveness of the model allows specification of the traditional mandatory access control models such as BLP, Biba, Dion, and Chinese Wall. The model can also be considered as an information flow control model with context-sensitive association of security classes.
H. Afzali; H. Nemati; R. Azmi
Abstract
Nowadays, users of information systems have inclination to use a central server to decrease data transferring and maintenance costs. Since such a system is not so trustworthy, users' data usually upkeeps encrypted. However, encryption is not a nostrum for security problems and cannot guarantee the data ...
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Nowadays, users of information systems have inclination to use a central server to decrease data transferring and maintenance costs. Since such a system is not so trustworthy, users' data usually upkeeps encrypted. However, encryption is not a nostrum for security problems and cannot guarantee the data security. In other words, there are some techniques that can endanger security of encrypted data. Majority of existing methods for encrypted data management have some critical defects such as cryptanalysis attacks, encryption/decryption overhead, and inefficient data storing and retrieval. In this paper, at first we propose a prototype model of private key based search on encrypted data. Then we try to improve it significantly to meet security requirements. Our main goal is to offer a practical method of querying arbitrary words on encrypted data using a minimal trust model. Moreover, we present a model for balancing between performance and security based on user's requirements. In comparison with other methods, query response time is improved and the probability of statistical deductions is reduced.
A. Mortazavi; M. Salmasizadeh; A. Daneshgar
Abstract
A non-malleable code is a variant of an encoding scheme which is resilient to tampering attacks. The main idea behind non-malleable coding is that the adversary should not be able to obtain any valuable information about the message. Non-malleable codes are used in tamper-resilient cryptography and protecting ...
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A non-malleable code is a variant of an encoding scheme which is resilient to tampering attacks. The main idea behind non-malleable coding is that the adversary should not be able to obtain any valuable information about the message. Non-malleable codes are used in tamper-resilient cryptography and protecting memories against tampering attacks. Many different types of non-malleability have already been formalized and defined in current literature, among which continuous non-malleability is the setup in which the messages are protected against adversaries who may issue polynomially many tampering queries. The first continuous non-malleable encoding scheme has been proposed by Faust et al. (FMNV) in 2014. In this article, we propose a new proof of continuous non-malleability of the FMNV scheme. The new proof will give rise to an improved and more efficient version of this scheme. Also, the new proof shows that one may achieve continuous non-malleability of the same security by using a leakage resilient storage scheme with fewer bits for the leakage bound. This shows that the new scheme is more efficient and practical for tamper-resilient applications.
Shahriar Mohammadi; Amin Namadchian
Abstract
Today, the use of the Internet and Internet sites has been an integrated part of the people’s lives, and most activities and important data are in the Internet websites. Thus, attempts to intrude into these websites have grown exponentially. Intrusion detection systems (IDS) of web attacks are ...
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Today, the use of the Internet and Internet sites has been an integrated part of the people’s lives, and most activities and important data are in the Internet websites. Thus, attempts to intrude into these websites have grown exponentially. Intrusion detection systems (IDS) of web attacks are an approach to protect users. But, these systems are suffering from such drawbacks as low accuracy in detecting new attacks. To tackle this problem, various methods of machine learning have been presented in recent years. Since malicious web requests have more delicate distinction than normal requests, these methods have failed to exhibit a good accuracy in new attack detection. This paper presents a new method for web attack detection using seq2seq networks using attention. The results show that this method could predict the possible responses and use the difference from the real responses of the server to model the normal traffic. Thereby, it could use the similarity measure to discriminate between normal and anomalous traffic. The highest accuracy of this method versus similar methods shows that the use of attention mechanism can cope with the challenge of studying long web requests to a great extent.
Reza Ebrahimi Atani; Shahabaddin Ebrahimi Atani; A. Hassani Karbasi
Abstract
In this paper we present a new finite field-based public key cryptosystem(NETRU) which is a non-commutative variant of CTRU. The original CTRU is defined by the ring of polynomials in one variable over a finite field F2. This system works in the ring R = F2[x]=hxN 1i and is already broken ...
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In this paper we present a new finite field-based public key cryptosystem(NETRU) which is a non-commutative variant of CTRU. The original CTRU is defined by the ring of polynomials in one variable over a finite field F2. This system works in the ring R = F2[x]=hxN 1i and is already broken by some attacks such as linear algebra attack. We extend this system over finite fields Zp, where p is a prime (or prime power) and it operates over the non-commutative ring M = Mk(Zp)[T; x]=hXn Ikki, where M is a matrix ring of k by k matrices of polynomials in R = Zp[T; x]=hxn 1i. In the proposed NETRU, the encryption and decryption computations are non-commutative and hence the system is secure against linear algebra attack as lattice-based attacks. NETRU is designed based on the CTRU core and exhibits high levels of security with two-sided matrix multiplication.
S. Sadat Emami; S. Zokaei
Abstract
Resources and services are accessible in pervasive computing environments from anywhere and at any time. Also, due to ever-changing nature of such environments, the identity of users is unknown. However, users must be able to access the required resources based on their contexts. These and other similar ...
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Resources and services are accessible in pervasive computing environments from anywhere and at any time. Also, due to ever-changing nature of such environments, the identity of users is unknown. However, users must be able to access the required resources based on their contexts. These and other similar complexities necessitate dynamic and context-aware access control models for such environments. In other words, an efficient access control model for pervasive computing environments should be aware of context information. Changes in context information imply some changes in the users' authorities. Accordingly, an access control model for a pervasive computing environment should control all accesses of unknown users to the resources based upon the participating context information, i.e., contexts of the users, resources and the environment. In this paper, a new context-aware access control model is proposed for pervasive computing environments. Contexts are classified into long-term contexts (which do not change during a session) and short-term contexts (which their steady-state period is less than an average time of a session). The model assigns roles to a user dynamically at the beginning of their sessions considering the long-term contexts. However, during a session the active permission set of the assigned roles are determined based on the short-term context conditions. Formal specification of the proposed model as well as the proposed architecture are presented in this paper. Furthermore, by presenting a real case study, it is shown that the model is applicable, decidable, and dynamic. Expressiveness and complexity of the model is also evaluated.
F. Sadeghi; F. Zarisfi Kermani; M. Kuchaki Rafsanjani
Abstract
In this study, a novel approach which uses combination of steganography and cryptography for hiding information into digital images as host media is proposed. In the process, secret data is first encrypted using the mono-alphabetic substitution cipher method and then the encrypted secret data is embedded ...
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In this study, a novel approach which uses combination of steganography and cryptography for hiding information into digital images as host media is proposed. In the process, secret data is first encrypted using the mono-alphabetic substitution cipher method and then the encrypted secret data is embedded inside an image using an algorithm which combines the random patterns based on Space Filling Curves (SFC) and the optimal pair-wise LSB matching method. We employ a modified Imperialist Competitive Algorithm by Genetic Algorithm operations, namely Discrete Imperialist Competitive Algorithm (DICA), to perform the optimal pair-wise LSB matching method and find the suboptimum adjustment list. The performance of the proposed method is compared with other methods with respect to Peak Signal to Noise Ratio (PSNR). The PSNR value of the proposed method is higher than the state-of-the-art methods by almost 4dB to 5dB.
Mansoureh Labbafniya; Roghaye Saeidi
Abstract
Nowadays there are different kinds of attacks on Field Programmable Gate Array (FPGA). As FPGAs are used in many different applications, its security becomes an important concern, especially in Internet of Things (IoT) applications. Hardware Trojan Horse (HTH) insertion is one of the major security threats ...
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Nowadays there are different kinds of attacks on Field Programmable Gate Array (FPGA). As FPGAs are used in many different applications, its security becomes an important concern, especially in Internet of Things (IoT) applications. Hardware Trojan Horse (HTH) insertion is one of the major security threats that can be implemented in unused space of the FPGA. This unused space is unavoidable to meet the place and route requirements. In this paper, we introduce an efficient method to fill this space and thus to leave no free space for inserting HTHs. Using a shift register in combination with gate-chain is the best way of filling unused space, which incurs a no increase in power consumption of the main design. Experimental results of implementing a set of IWLS benchmarks on Xilinx Virtex devices show that the proposed prevention and detection scheme imposes a no power overhead with no degradation to performance and critical path delay of the main design
M. Deljavan Amiri; H. Danyali; B. Zahir-Azami
Abstract
Image watermarking refers to the process of embedding an authentication message, called watermark, into the host image to uniquely identify the ownership. In this paper a novel, intelligent, scalable, robust wavelet-based watermarking approach is proposed. The proposed approach employs a genetic algorithm ...
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Image watermarking refers to the process of embedding an authentication message, called watermark, into the host image to uniquely identify the ownership. In this paper a novel, intelligent, scalable, robust wavelet-based watermarking approach is proposed. The proposed approach employs a genetic algorithm to find nearly optimal positions to insert watermark. The embedding positions coded as chromosomes and GA operators (e.g. selection, crossover, mutation and elitism), are used to find the nearly optimal embedding positions. A fitness function, which includes both factors related to transparency and robustness, is used to assess and compare chromosomes. The watermarked test images do not show any perceptual degradation. This approach supports scalable watermark detection and provides robustness against progressive wavelet image compression. The experimental results very efficiently prove the robustness of the approach against progressive wavelet image coding even at very low bit-rates and some other attacks. This approach is a good candidate for providing efficient authentication for secure and progressive image transmission applications especially over heterogeneous networks, such as the Internet.
H. Ghasemzadeh; A. Payandeh; M. R. Aref
Abstract
Due to wireless nature and hostile environment, providing of security is a critical and vital task in wireless sensor networks (WSNs). It is known that key management is an integral part of a secure network. Unfortunately, in most of the previous methods, security is compromised in favor of reducing ...
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Due to wireless nature and hostile environment, providing of security is a critical and vital task in wireless sensor networks (WSNs). It is known that key management is an integral part of a secure network. Unfortunately, in most of the previous methods, security is compromised in favor of reducing energy consumption. Consequently, they lack perfect resilience and are not fit for applications with high security demands. In this paper, a novel method is proposed to improve the security of key management system based on broadcast messages from the base station. Another problem with WSNs is the cryptographic materials (such as private keys) stored in dead nodes. Adversaries may exploit these nodes to mount more effective attacks. Any secure key management system should also address this problem. It is argued that in the proposed method keying materials of dead nodes lose their validity, and therefore are of no use for an adversary. Finally, it is shown through simulation that the proposed method is almost three times more energy-efficient than conventional certificate-based key management systems.
Sh. Zamanzadeh; A. Jahanian
Abstract
FPGA platforms have been widely used in many modern digital applications due to their low prototyping cost, short time-to-market and flexibility. Field-programmability of FPGA bitstream has made it as a flexible and easy-to-use platform. However, access to bitstream degraded the security of FPGA IPs ...
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FPGA platforms have been widely used in many modern digital applications due to their low prototyping cost, short time-to-market and flexibility. Field-programmability of FPGA bitstream has made it as a flexible and easy-to-use platform. However, access to bitstream degraded the security of FPGA IPs because there is no efficient method to authenticate the originality of bitstream by the FPGA programmer. The issue of secure transmission of configuration information to the FPGAs is of paramount importance to both users and IP providers. In this paper we presented a "Self Authentication" methodology in which the originality of sub-components in bitstream is authenticated in parallel with the intrinsic operation of the design. In the case of discovering violation, the normal data flow is obfuscated and the circuit would be locked. Experimental results show that this methodology considerably improves the IP security against malicious updates with reasonable overheads.
Mahdieh Ebrahimi; Majid Bayat; Behnam Zahednejad
Abstract
The medical system remains among the fastest to adopt the Internet of Things. The reason for this trend is that integration Internet of Things(IoT) features into medical devices greatly improve the quality and effectiveness of service. However, there are many unsolved security problems. Due to medical ...
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The medical system remains among the fastest to adopt the Internet of Things. The reason for this trend is that integration Internet of Things(IoT) features into medical devices greatly improve the quality and effectiveness of service. However, there are many unsolved security problems. Due to medical information is critical and important, authentication between users and medical servers is an essential issue. Recently, Park et al. proposed an authentication scheme using Shamir's threshold technique for IoT-based medical information system and claimed that their scheme satisfies all security requirements and is immune to various types of attacks. However, in this paper, we show that Park et al.'s scheme does not achieve user anonymity, forward security, and mutual authentication and it is not resistant to the DoS attacks and then we introduce an improved mutual authentication scheme based on Elliptic Curve Cryptography (ECC) and Shamir 's secret sharing for IoT-based medical information system.In this paper, we formally analyze the security properties of our scheme via the ProVerif. Moreover, we compare our proposed scheme with other related schemes in terms of security and performance.
Salome James; Gowri Thumbur; P.Vasudeva Reddy
Abstract
In recent years, due to their potential applications, proxy blind signatures became an active research topic and are an extension of the basic proxy signature. A proxy blind signature scheme enables a proxy signer to produce a blind signature on behalf of an original signer. Such schemes are useful in ...
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In recent years, due to their potential applications, proxy blind signatures became an active research topic and are an extension of the basic proxy signature. A proxy blind signature scheme enables a proxy signer to produce a blind signature on behalf of an original signer. Such schemes are useful in many practical applications such as e-commerce, e-voting, e-tendering systems. Many proxy blind signature schemes have been proposed in the literature. In order to improve the efficiency and to adopt resource constrained devices, in this paper, we propose a pairing free ID-based proxy blind signature scheme with message recovery. The proposed scheme is proven secure against the random oracle model under the hardness assumption of the elliptic curve discrete logarithm problem. We compare our scheme with the other proxy blind signature schemes. The efficiency analysis shows that our scheme is more efficient in terms of computational and communicational point of view. Also due to the message recovery property, our scheme can be deployed easily in low band width devices.
M. Ghiasi; A. Sami; Z. Salehi
Abstract
To control the exponential growth of malware files, security analysts pursue dynamic approaches that automatically identify and analyze malicious software samples. Obfuscation and polymorphism employed by malwares make it difficult for signature-based systems to detect sophisticated malware files. The ...
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To control the exponential growth of malware files, security analysts pursue dynamic approaches that automatically identify and analyze malicious software samples. Obfuscation and polymorphism employed by malwares make it difficult for signature-based systems to detect sophisticated malware files. The dynamic analysis or run-time behavior provides a better technique to identify the threat. In this paper, a dynamic approach is proposed in order to extract features from binaries. The run-time behavior of the binary files were found and recorded using a homemade tool that provides a controlled environment. The approach based on DyVSoR assumes that the run-time behavior of each binary can be represented by the values of registers. A method to compute the similarity between two binaries based on the value sets of the registers is presented. Hence, the values are traced before and after invoked API calls in each binary and mapped to some vectors. To detect an unknown file, it is enough to compare it with dataset binaries by computing the distance between registers, content of this file and all binaries. This method could detect malicious samples with 96.1% accuracy and 4% false positive rate. The list of execution traces and the dataset are reachable at: http://home.shirazu.ac.ir/˷ sami/malware
Sina Abdollahi; Javad Mohajeri; Mahmoud Salmasizadeh
Abstract
Ciphertext-policy attribute-based encryption(CP-ABE) is considered a promising solution for secure data sharing in the cloud environment. Although very well expressiveness in ABE constructions can be achieved using a linear secret sharing scheme(LSSS), there is a significant drawback in such constructions. ...
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Ciphertext-policy attribute-based encryption(CP-ABE) is considered a promising solution for secure data sharing in the cloud environment. Although very well expressiveness in ABE constructions can be achieved using a linear secret sharing scheme(LSSS), there is a significant drawback in such constructions. In the LSSS-based ABE constructions, the number of heavy pairing operations increases with an increase in the number of required attributes in the decryption. In this paper, we propose an LSSS-based CP-ABE scheme with a fixed number of pairings(four pairings) during the decryption process. In our scheme increasing the number of required attributes in the decryption does not affect the number of pairings. The simulation shows that our scheme has significant advantages in the encryption and the decryption processes compared to previous schemes. In addition, we use the outsourcing method in the decryption to get better performance on the user side. The main burden of decryption computations is done by the cloud without revealing any information about the plaintext. Furthermore, in our revocation method, the users’ communication channels are not used during the revocation process. All of these features make our scheme suitable for applications such as IoT. The proposed scheme is selectively CPA-secure in the standard model.
Mahsa Nooribakhsh; Mahdi Mollamotalebi
Abstract
Distributed Denial of Service (DDoS) is a common attack in recent years that can deplete the bandwidth of victim nodes by flooding packets. Based on the type and quantity of traffic used for the attack and the exploited vulnerability of the target, DDoS attacks are grouped into three categories as Volumetric ...
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Distributed Denial of Service (DDoS) is a common attack in recent years that can deplete the bandwidth of victim nodes by flooding packets. Based on the type and quantity of traffic used for the attack and the exploited vulnerability of the target, DDoS attacks are grouped into three categories as Volumetric attacks, Protocol attacks and Application attacks. The volumetric attack, which the proposed method attempts to detect it, is the most common type of DDoS attacks. The aim of this paper is to reduce the delay of real-time detection of DDoS attacks utilizing hybrid structures based on data stream algorithms. The proposed data structure (BHM ) improves the data storing mechanism presented in STONE method and consequently reduces the detection time. STONE characterizes regular network traffic of a service by aggregating it into common prefixes of IP addresses, and detecting attacks when the aggregated traffic deviates from the regular one. In BHM, history refers to the output traffic information obtained from each monitoring period to form a reference profile. The reference profile is created by employing historical information and only includes normal traffic information. The delay of DDoS attack detection increases in STONE due to long-time intervals between each monitoring period. The proposed method (F-STONE) has been compared to STONE based on attack detection time, Expected Profile Update Time (EPUT), and rate of attack detection. The evaluation results indicated significant improvements in terms of the EPUT, acceleration of attack detection and reduction of false positive rate.
M. Mahdavi Oliaee; M. Delavar; M.H. Ameri; J. Mohajeri; M.R. Aref
Abstract
In recent years, determining the common information privately and efficiently between two mutually mistrusting parties have become an important issue in social networks. Many Private Set Intersection (PSI) protocols have been introduced to address this issue. By applying these protocols, two parties ...
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In recent years, determining the common information privately and efficiently between two mutually mistrusting parties have become an important issue in social networks. Many Private Set Intersection (PSI) protocols have been introduced to address this issue. By applying these protocols, two parties can compute the intersection between their sets without disclosing any information about components that are not in the intersection. Due to the broad range of computational resources that the cloud can provide for its users, determining the set intersection by cloud may decrease the computational cost of the users. The proposed protocols by Abadi et al. are two protocols in this context. In this paper, we show that their protocols are vulnerable to eavesdropping attack. Also, a solution is proposed to secure the protocol against mentioned attack. Moreover, we analyze the performance of both O-PSI and modified O-PSI protocols and show that our scheme is comparable with the O-PSI protocol. Actually, one trivial solution for the Abadi et al.’s proposed schemes is to use a secure channel like TLS. However, in the performance evaluation, we compare our applied modification with this trivial solution, and show that our proposed modification is more efficient as some extra encryptions imposed by TLS are no longer required.
M. Abolghasemi; H. Aghaeinia; K. Faez
Abstract
Perturbed Quantization (PQ) steganography scheme is almost undetectable with the current steganalysis methods. We present a new steganalysis method for detection of this data hiding algorithm. We show that the PQ method distorts the dependencies of DCT coefficient values; especially changes much lower ...
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Perturbed Quantization (PQ) steganography scheme is almost undetectable with the current steganalysis methods. We present a new steganalysis method for detection of this data hiding algorithm. We show that the PQ method distorts the dependencies of DCT coefficient values; especially changes much lower than significant bit planes. For steganalysis of PQ, we propose features extraction from the empirical matrix. The proposed features can be exploited within an empirical matrix of DCT coefficients which some most significant bit planes were deleted. We obtain four empirical matrices and fuse resulted features from these matrices which have been employed for steganalysis. This technique can detect PQ embedding on stego images with 77 percent detection accuracy on mixed embedding rates between 0.05 _ 0.4 bits per non-zero DCT AC coefficients (BPNZC). Comparing the results, we also show that the detection rates are effectively comparable with respect to current steganalysis techniques for PQ steganography.
S. Soltani; M. A. Hadavi; R. Jalili
Abstract
Database outsourcing is an idea to eliminate the burden of database management from organizations. Since data is a critical asset of organizations, preserving its privacy from outside adversary and untrusted server should be warranted. In this paper, we present a distributed scheme based on storing shares ...
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Database outsourcing is an idea to eliminate the burden of database management from organizations. Since data is a critical asset of organizations, preserving its privacy from outside adversary and untrusted server should be warranted. In this paper, we present a distributed scheme based on storing shares of data on different servers and separating indexes from data on a distinct server. Shamir's secret sharing scheme is used for distributing data to data share servers. A B+-tree index on the order preserved encrypted values for each searchable attribute is stored in the index server. To process a query, the client receives responses including record numbers from the index server and asks these records from data share servers. The final result is computed by the client using data shares. While the proposed approach is secure against different database attacks, it supports exact match, range, aggregation, and pattern matching queries efficiently. Simulation results show the prominence of our approach in comparison with the bucketing scheme as it imposes lower computation and communication costs on the client.
Z. Zali; M. R. Hashemi; H. Saidi
Abstract
Alert correlation systems attempt to discover the relations among alerts produced by one or more intrusion detection systems to determine the attack scenarios and their main motivations. In this paper a new IDS alert correlation method is proposed that can be used to detect attack scenarios in real-time. ...
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Alert correlation systems attempt to discover the relations among alerts produced by one or more intrusion detection systems to determine the attack scenarios and their main motivations. In this paper a new IDS alert correlation method is proposed that can be used to detect attack scenarios in real-time. The proposed method is based on a causal approach due to the strength of causal methods in practice. To provide a picture of the current intrusive activity on the network, we need a real-time alert correlation. Most causal methods can be deployed offline but not in real-time due to time and memory limitations. In the proposed method, the knowledge base of the attack patterns is represented in a graph model called the Causal Relations Graph. In the offline mode, we construct Queue trees related to alerts' probable correlations. In the real-time mode, for each received alert, we can find its correlations with previously received alerts by performing a search only in the corresponding tree. Therefore, the processing time of each alert decreases significantly. In addition, the proposed method is immune to deliberately slowed attacks. To verify the proposed method, it was implemented and tested using DARPA2000 dataset. Experimental results show the correctness of the proposed alert correlation and its efficiency with respect to the running time.
M. Nikooghadam; A. Zakerolhosseini
Abstract
Elliptic Curve Cryptosystems (ECC) have recently received significant attention by researchers due to their high performance such as low computational cost and small key size. In this paper a novel untraceable blind signature scheme is presented. Since the security of proposed method is based on difficulty ...
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Elliptic Curve Cryptosystems (ECC) have recently received significant attention by researchers due to their high performance such as low computational cost and small key size. In this paper a novel untraceable blind signature scheme is presented. Since the security of proposed method is based on difficulty of solving discrete logarithm over an elliptic curve, performance of the proposed scheme is quite commendable in comparison with the previous work in terms of security and time complexity.
J. Alizadeh; M. R. Aref; N. Bagheri; H. Sadeghi
Abstract
ΑΕS _ CMCCv₁, ΑVΑLΑNCHEv₁, CLΟCv₁, and SILCv₁ are four candidates of the first round of CAESAR. CLΟCv₁ is presented in FSE 2014 and SILCv₁ is designed upon it with the aim of optimizing the hardware implementation cost. In this paper, structural ...
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ΑΕS _ CMCCv₁, ΑVΑLΑNCHEv₁, CLΟCv₁, and SILCv₁ are four candidates of the first round of CAESAR. CLΟCv₁ is presented in FSE 2014 and SILCv₁ is designed upon it with the aim of optimizing the hardware implementation cost. In this paper, structural weaknesses of these candidates are studied. We present distinguishing attacks against ΑES _ CMCCv₁ with the complexity of two queries and the success probability of almost 1, and distinguishing attacks on CLΟCv₁ and SILCv₁ with the complexity of Ο (2n/2) queries and the success probability of 0.63, in which n is bit length of message blocks. In addition, a forgery attack is presented against ΑVΑLΑNCHEv₁ which requires only one query and has the success probability of 1. The attacks reveal weaknesses in the structure of these first round candidates and inaccuracy of their security claims.
N. Zarmehi; M. R. Aref
Abstract
This paper investigates the multiplicative spread spectrum watermarking method for the image. The information bit is spreaded into middle-frequency Discrete Cosine Transform (DCT) coefficients of each block of an image using a generated pseudo-random sequence. Unlike the conventional signal modeling, ...
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This paper investigates the multiplicative spread spectrum watermarking method for the image. The information bit is spreaded into middle-frequency Discrete Cosine Transform (DCT) coefficients of each block of an image using a generated pseudo-random sequence. Unlike the conventional signal modeling, we suppose that both signal and noise are distributed with Laplacian distribution, because the sample loss of digital media can be better modeled with this distribution than the Gaussian one. We derive the optimum decoder for the proposed embedding method thanks to the maximum likelihood decoding scheme. We also analyze our watermarking system in the presence of noise and provide analytical evaluations and several simulations. The results show that it has the suitable performance and transparency required for watermarking applications.
H. Ghasemzadeh; M. Tajik Khasss; H. Mehrara
Volume 9, Issue 2 , July 2017, , Pages 131-145
Abstract
Recently permutation multimedia ciphers were broken in a chosen-plaintext scenario. That attack models a very resourceful adversary which may not always be the case. To show insecurity of these ciphers, we present a cipher-text only attack on speech permutation ciphers. We show inherent redundancies ...
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Recently permutation multimedia ciphers were broken in a chosen-plaintext scenario. That attack models a very resourceful adversary which may not always be the case. To show insecurity of these ciphers, we present a cipher-text only attack on speech permutation ciphers. We show inherent redundancies of speech can pave the path for a successful cipher-text only attack. To that end, regularities of speech are extracted in time and frequency using short time Fourier transform. We show that spectrograms of cipher-texts are in fact scrambled puzzles. Then, different techniques including estimation, image processing, and graph theory are fused together in order to create and solve these puzzles. Conducted tests show that the proposed method achieves accuracy of 87.8% and intelligibility of 92.9%. These scores are 50.9% and 34.6%, respectively, higher than scores of previous method. Finally a novel method, based on moving spectrogram distance, is proposed that can give accurate estimation of segment length of the scrambler system.
Siavash Ahmadi; Mohammad Reza Aref
Abstract
GOST block cipher designed in the 1970s and published in 1989 as the Soviet and Russian standard GOST 28147-89. In order to enhance the security of GOST block cipher after proposing various attacks on it, designers published a modified version of GOST, namely GOST2, in 2015 which has a new key schedule ...
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GOST block cipher designed in the 1970s and published in 1989 as the Soviet and Russian standard GOST 28147-89. In order to enhance the security of GOST block cipher after proposing various attacks on it, designers published a modified version of GOST, namely GOST2, in 2015 which has a new key schedule and explicit choice for S-boxes. In this paper, by using three exactly identical portions of GOST2 and fixed point idea, more enhanced fixed point attacks for filtration of wrong keys are presented. More precisely, the focus of the new attacks is on reducing memory complexity while keeping other complexities unchanged as well. The results show a significant reduction in the memory complexity of the attacks, while the time complexity slightly increased in comparison to the previous fixed point attacks. To the best of our knowledge, the lowest memory complexity for an attack on full-round GOST2 block cipher is provided here.