Sharif Digital Repository

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... 

Nowadays the Internet users are from different ages and groups. Disabled people are a group of the Internet users. Some websites are especially created for disabled people and public access to them is undesirable. In this paper, for the first time, a method is introduced for distinguishing between deaf persons and other users using a new HIP (Human Interactive Proofs) system. In this method, the sign language is used. A word is shown as a movie using a sign language. The user should recognize the word and select it from a list. Only deaf persons can understand sign language and recognize the word, therefore other persons and also computer programs cannot enter the website. This project has... 

Peer-to-peer streaming has recently gained attention as an effective solution to support large scale media streaming applications over the Internet. One of the main challenges of peer-to-peer video streaming is the cumulative impact of the Internet packet loss due to the decoding dependency of the compressed video frames. In this paper we study the impact of the Internet packet loss on the performance of peer-to-peer video streaming systems, and analyze the efficiency of various packet loss recovery policies in such systems. Our analytical and simulation results show how the Internet packet loss can affect the performance of peer- to-peer video streaming systems and how different packet loss... 

In line with the expansion of the Internet, the issue of information security has gained special importance. Many methods have been provided in order to establish hidden communications. In the meanwhile, steganography is one of a relatively new method. A method is introduced in this paper for exchanging information by steganography on HTML pages. The main idea in this method is to hide coded data in the ID attribute of the HTML document tags. Since numerous HTML pages are on the web, this method can be widely used. The suggested method is implemented by using the Java language. © 2006 Springer  

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... 

In this letter, we study large-scale networks in terms of observability and controllability. In particular, we compare the number of unmatched nodes in two main types of Scale-Free (SF) networks: the Barabási-Albert (BA) model and the Holme-Kim (HK) model. Comparing the two models based on theory and simulation, we discuss the possible relation between clustering coefficient and the number of unmatched nodes. In this direction, we propose a new algorithm to reduce the number of unmatched nodes via link addition. The results are significant as one can reduce the number of unmatched nodes and therefore number of embedded sensors/actuators in, for example, an IoT network. This may significantly... 

This study revisited the problem of online con ict-free coloring of intervals on a line, where each newly inserted interval must be assigned a color upon insertion such that the coloring remains conflict-free, i.e., for each point p in the union of the current intervals, there must be an interval I with a unique color among all intervals covering p. The bestknown algorithm uses O(log3 n) colors, where n is the number of current intervals. A simple greedy algorithm was presented that used only O(log n) colors. Therefore, the open problem raised in [Abam, M.A., Rezaei Seraji, M.J., and Shadravan, M. "Online conflictfree coloring of intervals", Journal of Scientia Iranica, 21(6), pp. 2138{2141... 

This study revisited the problem of online con ict-free coloring of intervals on a line, where each newly inserted interval must be assigned a color upon insertion such that the coloring remains conflict-free, i.e., for each point p in the union of the current intervals, there must be an interval I with a unique color among all intervals covering p. The bestknown algorithm uses O(log3 n) colors, where n is the number of current intervals. A simple greedy algorithm was presented that used only O(log n) colors. Therefore, the open problem raised in [Abam, M.A., Rezaei Seraji, M.J., and Shadravan, M. "Online conflictfree coloring of intervals", Journal of Scientia Iranica, 21(6), pp. 2138{2141... 

Transmission Control Protocol (TCP) uses multiple timers to do its work. The most important of these is the retransmission timer. In this paper, the TCP retransmission timer adjustment mechanism is approached from a system point of view and a new mechanism is proposed. A simple recursive system identification algorithm is used to capture both time variant and time invariant Internet behavior. Also a dynamic model-based Round-Trip Time (RTT) predictor was provided. Based on network simulation and real Internet data collection, it was observed that when the retransmission timer is adjusted by the proposed predictor instead of the traditional RTT estimator, performance increased significantly  

With the widespread use of Internet of Things (IoT) in every aspect of human's daily life, communications of such an enormous amount of existing embedded devices in these systems arise many new challenges from power consumption, performance, and reliability perspectives. Communications in an IoT infrastructure are managed by a set of policies which are determined by Objective Functions (OFs). Thus, OFs are the most important contributors in facing with the mentioned challenges. In this paper, due to the lack of information on how OFs affect the primary properties of an IoT infrastructure, we have compared three well-known OFs (OF0, MRHOF, and OFFL) from power consumption, performance, and... 

Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of quick and accurate authentication or identification. In many cases, it has been shown that if such systems are not properly designed, an adversary can cause security and privacy concerns for end-users. In order to deal with these concerns, impressive endeavors have been made which have resulted in various RFID authentications being proposed. In this study, we analyze three lightweight RFID authentication protocols proposed in Wireless Personal Communications (2014), Computers & Security (2015) and Wireless Networks... 

Internet of Things (IoT) devices have strict necessity for power consumption in order to achieve expected battery life. IoT nodes feature extreme power consumption range over 100 dB, between their operating modes. The main focus of this paper is to design and implement a high precision, high dynamic range, low power, and flexible power measurement system, which can be applied to different applications. The proposed system consists of a voltage regulating control loop, zero offset amplifiers, high precision analog to digital converters, and reference voltage. The proper operation of the proposed circuit are verified numerically with simulations and experimental measurements. The implemented... 

Lightweight authentication protocols are crucial for privacy preserving in Internet of Things (IoT). Authentication protocols should be implementable for devices with constrained memory and computational power in this area, in addition to resistance against cryptographic threats. On the other hand, these protocols should not impose a heavy computational load on such devices. In this paper we proposed an authentication protocol that properly meets these features. Our protocol is suitable for wireless sensor networks (WSNs). In this protocol, authentication is fulfilled with low communication and computational loads between sensors and users through the gateway interface using a hash function... 

Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of quick and accurate authentication or identification. In many cases, it has been shown that if such systems are not properly designed, an adversary can cause security and privacy concerns for end-users. In order to deal with these concerns, impressive endeavors have been made which have resulted in various RFID authentications being proposed. In this study, we analyze three lightweight RFID authentication protocols proposed in Wireless Personal Communications (2014), Computers & Security (2015) and Wireless Networks... 

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,... 

While the Internet of Things (IoT) shapes the future of the Internet, communications among nodes must be secured by employing cryptographic schemes such as public-key encryption (PKE). However, classic PKE schemes, such as RSA and elliptic curve cryptography (ECC) suffer from both high complexity and vulnerability to quantum attacks. During the past decade, post-quantum schemes based on the learning with errors (LWEs) problem have gained high attention due to the lower complexity among PKE schemes. In addition to resistance against theoretical (quantum and classic) attacks, every practical implementation of any cryptosystem must also be evaluated against different side-channel attacks such... 

This research aims to represent a novel approach to detect malicious nodes in Ad-hoc On-demand Distance Vector (AODV) within the next-generation smart cities. Smart city applications have a critical role in improving public services quality, and security is their main weakness. Hence, a systematic multidimensional approach is required for data storage and security. Routing attacks, especially sinkholes, can direct the network data to an attacker and can also disrupt the network equipment. Communications need to be with integrity, confidentiality, and authentication. So, the smart city and urban Internet of Things (IoT) network, must be secure, and the data exchanged across the network must... 

This article is concerned with remote monitoring and control of the 2-degrees of freedom (DoF) robotic manipulators, which have nonlinear dynamics over the packet erasure channel, which is an abstract model for communication over the Internet, WiFi, or Zigbee modules. This type of communication is subject to imperfections, such as random packet dropout and rate distortion. These imperfections cause a significant challenge for monitoring and control of robotic manipulators in the industrial environments because sensitive data, such as sensor data and control commands may not ever reach to their destination resulting in significant performance degradation. Therefore, the effects of these... 

This article reports the development of a new smart electrocardiogram (ECG) monitoring system, consisting of the related hardware, firmware, and Internet of Things (IoT)-based web service for artificial intelligence (AI)-assisted arrhythmia detection and a complementary Android application for data streaming. The hardware aspect of this article proposes an ultralow power patch sampling ECG data at 256 samples/s with 16-bit resolution. The battery life of the device is two weeks per charging, which alongside the flexible and slim (193.7 mm times62.4 mm times8.6 mm) and lightweight (43 g) allows the user to continue real-life activities while the real-time monitoring is being done without... 

The Social Internet of Things (SIoT), integration of the Internet of Things, and Social Networks paradigms, has been introduced to build a network of smart nodes that are capable of establishing social links. In order to deal with misbehaving service provider nodes, service requestor nodes must evaluate their trustworthiness levels. In this article, we propose a novel trust management mechanism in the SIoT to predict the most reliable service providers for each service requestor, which leads to reduce the risk of being exposed to malicious nodes. We model the SIoT with a flexible bipartite graph (containing two sets of nodes: service providers and service requestors), then build a social...