Sharif Digital Repository

Powerful universal steganalyzers were proposed in the literature during the past few years. In addition some studies have been conducted on improvements of current steganalysis results using information fusion techniques, merging available feature vectors, etc. This paper presents two independent ideas, which can be used together, to obtain higher accuracy in detecting stego images. First, we propose the use of boosted fusion methods to aggregate outputs of multiple steganalyzers. Second, we investigate how passing high frequencies through filtering can enhance the results of steganalysis techniques. In this work, it is shown that, through different tests over the state-of-the-art... 

After the emergence of modern technologies in the field of information technologies (IT), virtual learning has attained a new form. The way of announcing exams' grades is an important topic in e-learning. For announcing exams' grades on the web, various methods have been proposed. In this paper, first some common methods for announcing students' grades are reviewed, then three new methods which are named "Virtual Grade", "Steganography Grades", and "Grade HIP" are introduced and the result of implementing these methods for announcing the grades of some courses at the some Iranian universities are provided. Also these methods and their results are analyzed. Finally these three new methods are... 

A Publicly Verifiable Secret Sharing (PVSS) scheme, as introduced by Stadler, has a feature where anyone, besides the participants, can verify the validity of the shares distributed by the dealer. Schoenmakers added a new feature, by providing a proof of correctness of the shares released by the players in the reconstruction process. This protocol is claimed to be an improvement on Stadler's and Fujisaki-Okamoto's, both in efficiency and in the type of intractability assumptions. However, Young-Yung improved Schoenmakers' PVSS, using a Discrete-Log instead of a Decision Diffie-Hellman. In this paper, a new PVSS is presented, having an intrinsic difference with its predecessors, that is, the... 

This paper introduces a novel, cost effective visual cryptography scheme suitable for color image transmission over bandwidth constraint channels. Unlike previously proposed schemes, the solution offers perfect reconstruction while producing shares with size smaller than that of the input image. The maximum distance separable (MDS) code principle used in the design allows for the introduction of a flexible framework that compares favorably to competing solutions as it can be seen by examining the experimental results included in this paper. ©2008 IEEE  

In this work, we have examined the problem of distributed consensus averaging over senor networks from a novel point of view considering the need for security. We have proposed a method for incorporating privacy into the scalable average consensus mechanisms. Our proposed method, Random Projections Method (RPM), is lightweight and transparent since it is not based on cryptography and does not require any change in the fusion system. RPM is based on introducing a simple, yet effective pre-fusion algorithm. We mathematically derived the correctness of RPM and analyzed its effect on convergence of the system through simulation. Robustness of RPM against honest-but-curious adversaries is... 

Recently, Grid infrastructures have provided wide integrated use of resources. DotGrid intends to introduce required Grid services and toolkits that are implemented as a layer wrapped over the existing operating systems. Our DotGrid has been developed based on Microsoft .NET in Windows and MONO .NET in Linux and UNIX. Using DotGrid APIs, Grid middlewares and applications can be implemented easily. We evaluated our DotGrid capabilities by implementing some applications including a grid-based distributed cryptographic engine and also a typical computational problem. © 2006 IEEE  

Following the expansion of Internet, many software were produced that could launch through Internet without prior installation on computers. This included game software and software that deal with financial affairs. These softwares are mainly in Java language and can be found on web pages as Java Applets. Some software owners want that their products only able to execute through their own web pages so that no one could put them on other web pages. In this paper, a new method has been presented to protect Java Applets from copying by using "Steganography in HTML web pages" method. In this method, a special 8-character string is hidden in the HTML page by a secret key. The string and the... 

In this paper, a new multi-secret threshold scheme based on linear algebra and matrices is proposed. Unlike many recently proposed methods, this method lets the use of conventional cryptographic algorithms in sharing multiple secrets. Our scheme is a multi-use scheme, which in some cases, the amount of computations is considerably reduced. Also, in this paper bounds on the maximum number of participants, for a given threshold value, are obtained. © 2010  

A quantum protocol for secure transmission of data using qubits is presented. This protocol sends one qubit in a round-trip to transmit one bit of data. The protocol offers an improvement over the BB84 QKD protocol. BB84, in conjunction with one-time pad encryption, has been shown to be unconditionally secure. However its security relies on the assumption that the qubit source device does not emit multiple replicas of the same qubit for each transmitted bit. If this happens a multi-qubit emission attack can be launched. In addition, BB84 cannot be used to send predetermined bit strings as it generates a random bit string in the process. Our protocol does not have the above drawbacks, but... 

Establishing hidden communication is an important subject of discussion that has gained increasing importance nowadays with the development of the Internet. One of the methods introduced for establishing hidden communication is steganography. Methods of steganography have been mostly applied on images while the major characteristic of these methods is the change in the structure and features of the images so as not to be identifiable by human users. However, on the other hand, many methods have been proposed for breaking and extracting information (steganalysis) for these methods. This paper presents a method for hiding information in images by changing the appearance of the picture instead... 

Database management systems (DBMS) are one of cloud services with major applications in industry and business. In the use of such services, since the cloud service provider cannot be entrusted with the plain data, the databases are typically encrypted prior to outsourcing. One of the most challenging issues in designing these services is supporting SQL join queries on the encrypted database. The multi-adjustable join scheme (M-Adjoin) [Khazaei-Rafiee 2020], an extension of Adjoin [Popa-Zeldovich 2012 and Mironov-Segev-Shahaf 2017], is a symmetric-key primitive that supports the join queries for a list of column labels on an encrypted database. In previous works, the following security... 

A Wireless sensor network (WSN) is composed of numerous sensor nodes with both insecurely limited hardware and restricted communication capabilities. Thus WSNs suffer from some inherent weaknesses. Key management is an interesting subject in WSNs because it is the fundamental element for all security operations. A few key management models for heterogeneous sensor networks have been proposed in recent years. In this paper, we propose a new key management scheme based on elliptic curve cryptography and signcryption method for hierarchical heterogeneous WSNs. Our scheme as a secure infrastructure has superior sensor node mobility and network scalability. Furthermore, we propose both a periodic... 

McEliece and Goldreich–Goldwasser–Halevi (GGH) cryptosystems are two instances of code and lattice-based cryptosystems whose security are based on the hardness of coding theoretic and lattice problems, respectively. However, such cryptosystems have a number of drawbacks which make them inefficient in practice. On the other hand, low density lattice codes (LDLCs) are practical lattice codes which can achieve capacity over additive white Gaussian noise channel and also can be encoded and decoded efficiently. This paper introduces a public key cryptosystem based on Latin square LDLCs, by which a relationship can be attained between code and lattice-based cryptography. In this way, we can... 

Elliptic curve cryptography (ECC) has received attention, because it can achieve the same security level as other asymmetric methods while using a key with smaller length. Although ECC is more efficient compared with other asymmetric methods, the fast computation of ECC is always desirable. In this paper, a fixed-base comb point multiplication method has been used to perform regular point multiplication. In addition, two low-complexity (LC) and low-latency (LL) architectures for the regular point multiplication using fixed-base comb method have been proposed. The point multiplication architectures have been implemented using field-programmable gate array and application-specific integrated... 

With the exponential growth in the internet of things (IoT) applications such as smart city and e-health, more embedded devices and smart nodes are connected to the network. In order to provide security for such resource-constrained devices, different cryptographic schemes such as public key encryption (PKE) are required. However, considering the high complexity and vulnerability of classic PKE schemes against quantum attacks, it is necessary to consider other possible options. Recently, lattice-based cryptography and especially learning with errors (LWE) have gained high attention due to resistance against quantum attacks and relatively low-complexity operations. During the past decade,... 

Multi-party computation (MPC) allows each peer to take part in the execution of a common function with their private share of data without the need to expose it to other participants. The Legendre symbol is a pseudo-random function (PRF) that is suitable for MPC protocols due to their efficient evaluation process compared to other symmetric primitives. Recently, Legendre-based PRFs have also been employed in the construction of a post-quantum signature scheme, namely LegRoast. In this paper, we propose, to the best of our knowledge, the first hardware implementations for the Legendre symbol by three approaches: 1) low-area, 2) high-speed, and 3) high-frequency. The high-speed architecture...