Sajad Shirali-Shahreza's research while affiliated with University of Toronto and other places

Publications (75)

Article
Limited flow table size in switches is a major concern for SDN applications. The common approach to overcome this problem is to identify elephant flows and solely focus on them. However, there is no gold standard to assess the effectiveness of such greedy solutions. In this paper, we formally define this problem by choosing a cost function (hit rat...
Article
Internet-connected consumer electronics marketed as smart devices (aka Internet-of-Thing devices) usually lack essential security protection mechanisms. This puts user privacy and security in great danger. One of the essential steps to compromise vulnerable devices is locating them through horizontal port scans. In this paper, we focus on the probl...
Article
The ability to manage individual flows is a major benefit of Software-Defined Networking. The overheads of this fine-grained control, e.g. initial flow setup delay, can overcome the benefits, for example when we have many time-sensitive short flows. Coarse-grained control of groups of flows, on the other hand, can be very complex: each packet may m...
Article
One of the limitations of wildcard rules in Software Defined Networks, such as OpenFlow, is losing visibility. FleXam is a flexible sampling extension for OpenFlow that allows the controller to define which packets should be sampled, what parts of each packet should be selected, and where they should be sent. Here, we present an interactive demo sh...
Conference Paper
Current OpenFlow specifications provide limited access to packet-level information such as packet content, making it very inefficient, if not impossible, to deploy security and monitoring applications as controller applications. In this paper, we propose FleXam, a flexible sampling extension for OpenFlow designed to provide access to packet level i...
Conference Paper
It seems natural to imagine that SDN policy specification and control is distributed, and this paper focuses on the resulting concurrency issues. Indeed, conflicts among concurrent policy updates may result in serious inconsistencies on the data plane, ...
Conference Paper
Packet level information, such as packet content and inter-arrival time, are necessary for some network monitoring and control applications. However, current Software Defined Networks (SDN) such as OpenFlow provide limited access to packet-level information in the controller. In this paper, we propose an extension that enables the controller to acc...
Conference Paper
Speech certainly has advantages as an input modality for smartphone applications, especially in scenarios where using touch or keyboard entry is difficult, on increasingly miniaturized devices where useable keyboards are difficult to accommodate, or in scenarios where only small amounts of text need to be input, such as when entering SMS texts or r...
Chapter
Human Interactive Proof (HIP) systems have been introduced to distinguish between various groups of users. CAPTCHA methods are one of the important branches of HIP systems, which are used to distinguish between human users and computer programs automatically and block automated computer programs form abusing Web services. The goal of these systems...
Conference Paper
Speech authentication protocols should have a challenge/response feature to be protected against replay attacks. As a result, they need to verify whether the user responded to an interactive prompt. However, it is usually assumed that the user will provide their answer perfectly. In this paper, we report on an ecologically valid user study that we...
Article
CAPTCHA (Completely Automatic Public Turing Test to Tell Computer and Human Apart) systems are a group of methods designed to distinguish between real human users and computer programs that are interacting with the system. Their goal is to ask questions which human users can easily answer, but current computers cannot. So their evaluation can be do...
Article
CAPTCHA (Completely Automatic Public Turing Test to Tell Computer and Human Apart) systems are used to distinguish human users from computer programs automatically. The goal of them is to ask questions which human users can easily answer, but current computers cannot. Most current CAPTCHA methods are based on the weak points of OCR (Optical Charact...
Conference Paper
Verifying that a live human is interacting with an automated speech based system is needed in some applications such as biometric authentication. In this paper, we present a method to verify that the user is human. Simply stated, our method asks the user to repeat a sentence. The reply is analyzed to verify that it is the requested sentence and sai...
Conference Paper
There are many websites specially designed for mobile phones. Some hackers write automated programs to abuse these website services and waste the website resources. Therefore, it is necessary to distinguish between human users and computer programs. Methods known for achieving this are known as CAPTCHA (Completely Automated Public Turing test to te...
Conference Paper
Video compression algorithms are time consuming processes. A key part of video compression algorithms which is also time consuming is motion estimation (ME) and computation of motion vectors (MVs). During this process, a series of candidate blocks should be searched to find the best motion vectors. In this paper, we propose a method for reducing th...
Conference Paper
Mel Frequency Cepstral Coefficients (MFCC) are widely used in speech recognition and speaker identification. MFCC features are usually pre-processed before being used for recognition. One of these pre-processing is creating delta and delta-delta coefficients and append them to MFCC to create feature vector. Another pre-processing is coefficients me...
Article
Embedding a secret message into a cover media without attracting any attention, known as steganography, is one of the methods used for hidden communication purposes. One of the cover media that can be used for steganography is speech. In this study, the authors propose a new steganography method in speech signals. In this method, the silence interv...
Article
Nowadays, a great amount of information is circulated through the Internet. Some of them exclusively belong to a special group of users and require protection and safeguarding against unauthorized access. To this end, a category of systems called HIP (Human Interactive Proof) are designed to distinguish between various groups of users. An important...
Article
The mobile phone is one of the technologies which are widely used these days. It is available in most countries and all people, even children and elderly people can use it. It seems that in the near future, each person will have at least one mobile phone. So it is a good choice for communication in emergency situations, such as a heart attack or af...
Article
Digital music is now widely used and a great number of digital music files are available on the Internet. Designing systems that can automatically index, search and retrieve the digital music is one of the active research fields. One of the requirements for design and evaluation of such systems is corpuses of digital music samples. A good corpus is...
Conference Paper
Clustering is a major task in data mining which is used in many applications. However, general clustering is inappropriate for many applications where some constraints should be applied. One category of these constraints is the cluster size constraint. In this paper, we propose a new algorithm for solving the clustering with balancing constraints b...
Conference Paper
Today, the Internet is used to offer different services to users. Most of these services are designed for human users, but unfortunately some computer programs are designed which abuse these services. CAPTCHA (completely automated public Turing test to tell computers and human apart) systems are designed to automatically distinguish between human u...
Article
Digital music technologies enable users to create and use large collections of music. One of the desirable features for users is the ability to automatically organize the collection and search in it. One of the operations that they need is automatic identification of tracks' artists. This operation can be used to automatically classify new added tr...
Conference Paper
Speech is one of the main communication methods used by humans. So designing speech based interfaces for computer applications can ease the use of them for different users, especially disabled and elderly people. In this project, we want to design and implement a system that can identify user’s group from his/her speech. We are working on two main...
Conference Paper
Motion estimation (ME) is one of the key parts of video compression algorithms. But, motion estimation and computation of motion vectors (MVs) are very time consuming. In this paper, we propose a method for reducing the cost of motion estimation process. During this process, a series of candidate blocks should be searched to find the best motion ve...
Conference Paper
Feedback vibration is a standard feature in almost every home video game console controller to vibrate in selected circumstances, such as when the user's character kick the ball or hit the opponent, to immerse the player in the game. In the handheld game consoles this feature causes the handheld game consoles to vibrate. But the handheld game conso...
Conference Paper
SMS (short message service) is a popular service for transferring and exchange of short text messages between mobile phones. MMS (Multimedia Messaging Service) is another technology in mobile phones for creating, sending, receiving and storing messages that include text, images, audio and video clips. But MMS is not available in some countries. So,...
Conference Paper
Clustering is the problem of partitioning a (large) set of data using unsupervised techniques.Today, there exist many clustering techniques. The most important characteristic of a clustering technique is the shape of the cluster it can find. In this paper, we propose a method that is capable to find arbitrary shaped clusters and uses simple geometr...
Conference Paper
Multimedia files including audio, music and movies are important part of resources available on the Internet. With the expansion of personal computers and other digital devices such as digital cameras, ordinary people are also creating different multimedia files. Hence, there are huge amount of multimedia files in the Internet. Considering the volu...
Conference Paper
Nowadays, a great amount of information is circulated through the Internet. Some of them exclusively belongs to a special group of users and requires protection and safeguarding against unauthorized access. To this end, a category of systems called HIP (Human Interactive Proof) have been introduced to distinguish between various groups of users. CA...
Conference Paper
Steganography is a method for hidden exchange of information by hiding data in a cover media such as image or sound. Text Steganography is one of the most difficult methods because a text file is not a proper media to hide data in it. In this paper we propose a new text Steganography method. In this method, we hide data in TeX documents. This metho...
Article
One of the methods introduced for establishing hidden communication is steganography. Steganography is the art of hiding information in a cover media without attracting attention. Text documents are one of the common cover media used for steganography in past. Steganography in text is more difficult than other media because there is a little redund...
Conference Paper
One of the important problems in knowledge discovery from data is clustering. Clustering is the problem of partitioning a set of data using unsupervised techniques. An important characteristic of a clustering technique is the shape of the cluster it can find. Clustering methods which are capable to find simple cluster shapes are usually fast but in...
Conference Paper
Sending information secretly and communicating covertly have been of great interest for ages. On the other hand, text documents have been widely used and consequently various methods for hiding information in texts (text steganography) have been developed so far. In this paper a new method is proposed to hide information in digital Persian and Arab...
Conference Paper
Covert exchange of information has been long a significant and highlighted affair. Numerous methods have been devised for the matter of which steganography is a popular one. Already applied in the past, the method has been massive used following the invention of computer. This paper discusses a new application of steganography in textiles in which...
Article
Registration Websites use CAPTCHA (completely automated public turing test to tell computers and human apart) systems to prevent the bot programs from wasting their resources. But sometimes the CAPTCHA test is difficult for human users to pass because the users have different ages, languages, etc. In this paper we propose a solution for this proble...
Article
Establishing hidden communication is an important subject that nowadays has gained increasing importance. Embedding a secret message into a cover media without attracting any attention, known as steganography, is one of the methods used for hidden communication purposes. In this paper, we present an advanced version of ldquoCollage Steganographyrdq...
Conference Paper
In recent years Open Source Software programs have caused great changes in software world. Open Source software development is something beyond a method of software development or technology. As a result, using open source software development has diverse aspects. In this article the open source software development has been studied and investigate...
Conference Paper
There are many Web site on the Internet which are for adult users and we want to restrict access to them for adults only. Adult content filtering programs on client computers are the current available solutions. But if we can identify the child users at server side, we can protect the children more, In this paper., we try to answer the question tha...
Conference Paper
This paper presents a new approach for hiding information in speech signals. In this method, the silence intervals of speech are found and the length (number of samples) of these intervals is changed to hide information. This method can be used simultaneously with other methods.
Conference Paper
Skin detection has different applications in computer vision such as face detection, human tracking and adult content filtering. One of the major approaches in skin detection is pixel based skin detection which mark pixels as skin pixels based on their color. In this paper, we formally define the pixel based skin detection problem and model skin de...
Conference Paper
Nowadays, computer is being used in many aspects of human life. A consequence of computer is electronic documents. Computers cannot understand written documents. So, we need to convert written documents to electronic documents in order to be able to process them with computers. One of the common methods for converting written texts to electronic te...
Article
Restricting children access to materials unsuitable for them such as violence scenes is very important for parents. So there is a feature named Parental Control in devices such as televisions and computers to define the contents children can access. The parental control setting must be protected from children and is usually done by a password. In t...
Article
Nowadays the Internet users are from different ages and groups. The disabled people also use the Internet. Some Web sites are especially created for disabled people. Many Internet sites offers services for human users, but unfortunately some computer programs are designed to abuse these services. To solve this problem, some systems named CAPTCHA (c...
Conference Paper
Full-text available
Today, many students are study computer science. Although they study different courses, they rarely do homework or projects related to real world problems. In this paper, we design a project to show some of the problems which are occured during implementing a real word project to the students. In this project, the students are asked to implement th...
Conference Paper
In some websites it is necessary to distinguishing between human users and computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR systems and using them are undesirable to human users. In this paper a method has been presente...
Conference Paper
In some Websites it is necessary to distinguish between human users and computer programs which is known as CAPTCHA (completely automated public turing test to tell computers and human apart). CAPTCHA methods are mainly based on the weaknesses of OCR systems while using them are undesirable to human users. In this paper a new CAPTCHA method is intr...
Conference Paper
Watermarking is the process of hiding information in a media and usually used to for copyright protection. In software watermarking, the information is added to the source code of program and can be extracted from compiled executable code. In this paper, a new software watermarking algorithm is proposed by equation reordering. In this method, the o...
Conference Paper
Full-text available
Some Internet Web sites for providing services to their customers, ask them to register in the Web site. Unfortunately hackers write programs to make automatic false enrollments which waste the Web site's resources. To solve this problem, systems known as CAPTCHA (completely automated public Turing test to tell computers and humans apart) have been...
Conference Paper
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...
Conference Paper
Nowadays the Internet users are from different ages and groups. The disabled people also use the Internet. Some websites are especially created for disabled people. Many Internet sites offers services for human users, but unfortunately some computer programs are designed which abuse these services. As a result some systems named CAPTCHA (Completely...
Conference Paper
Full-text available
Today there are many Internet sites which require only the entry by human users but unfortunately some computer softwares called bots are designed by some hackers to enter these sites and use their resources through false registration. As a result some systems named CAPTCHA have been introduced to tell apart human users and computer software. This...
Article
Skin detection has different applications in computer vision such as face detection, human tracking and adult content filtering. One of the major approaches in pixel based skin detection is using Bayesian classifiers. Bayesian classifiers performance is highly related to their training set. In this paper, we introduce a new Bayesian classifier skin...
Conference Paper
In some websites, it is necessary to distinguish between human users and computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weaknesses of OCR systems while using them are undesirable to human users and cannot be used in some devices such as...
Conference Paper
Reusing the programs which have already been developed can shorten the production time and reduce costs and expenses. One of the important issues in software reuse is finding a program or a program component in a program library which has been already developed and using it in the new program. In view of precision and automation that formal methods...
Conference Paper
Full-text available
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 these people. One group of the disabled people are deaf persons. They have a special talking language which is named sign language. Here we present a method to encourage them, esp. children, to...
Conference Paper
In last 20 years, the Internet and mobile communication growth in parallel. There are many sites specially designed for mobile phones that users must enter username and password to enter them. In this paper we introduce a new method based on CAPTCHA which does not require entering any password. Instead of entering the password, an image of a number...
Conference Paper
Embedding a secret message into a cover media without attracting attention, which is known as steganography, is desirable in some security applications. One of the medias which can be used as a cover media is audio signal. In this paper we introduce an adaptive wavelet domain steganography with high capacity and low error rate. We use lifting schem...
Conference Paper
In some websites it is necessary to tell apart human users from computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR systems while using them are undesirable to human users. In this paper a method has been presented for tel...
Conference Paper
Nowadays a great deal of information is circulated through the Internet. Some of it exclusively belongs to a special group of people and requires protection and safeguarding against unauthorized access. To this end some systems called HIP (human interactive proofs) have been introduced to tell humans and computers apart or various groups of people...
Conference Paper
Full-text available
Today sending spams has turned to be a major problem in the Internet. It is so serious that more than 80% of the transferred emails are spams. As a result, various methods have been proposed for preventing spams. One of these methods in this field is CAPTCHA (Completely Automatic Public Turing Test to tell Computer and Humans Apart) method. They ha...
Conference Paper
Using OCR programs is one of the best ways to convert written and printed documents into digital form. The first phase in OCR is segmenting the input image and identifying text and non-text regions. This paper proposes a new method for segmentation of Persian printed texts which is based on the ink spread effect. Considering that the Persian script...
Conference Paper
Nowadays, many daily human activities such as education, commerce, talks, etc. are carried out through the Internet. In cases such as the registering in websites, some hackers write programs to make automatic false enrolments which waste the resources of the website while this may even stop the entire website from working. Therefore, it is necessar...
Conference Paper
Virtual learning is a new idea that has attained a new form with the emergence of new technologies such as the Internet. One of the issues in the field of E-learning is the way of announcing exams' grades. In this paper, a new method is introduced for restricting public access to exams' grades on the web by using a new HIP (Human Interactive Proofs...
Conference Paper
Now we are able to offer numerous softwares for mobile phones after the advances in mobile phone industry. Most of these softwares should be bought in order that we can use them. Some of these softwares are sharewares and after buying them you have to insert a serial number given by the manufacturing company in order to activate the software. But t...
Conference Paper
Earthquake is one of the natural disasters which have a lot of victims each year. If the rescue mission for saving victims be done in first hours after the earthquake, the number of earthquake victims can be lowered. Different methods had been proposed to find victims under devastated buildings which some of them are expensive and time consuming an...
Conference Paper
Nowadays, OCR (optical character recognition) is widely used for converting written documents to digital documents. One of the OCR phases is page segmentation. In page segmentation, text regions must be found in input image. In addition, text parts like text columns must be separated. In this paper, a new method for segmenting Persian/Arabic printe...
Conference Paper
Nowadays, computer is being used in many aspects of human life. A consequence of computer is electronic documents. Computers can't understand written documents. So, we need to convert written documents to electronic documents in order to be able to process them with computers. One of the common methods for converting written texts to electronic tex...
Conference Paper
Digital documents are widely used today. So converting written documents such as books to digital documents is unavoidable. The most popular method for doing this is OCR. Usually documents are scanned and then scanned images are sent to OCR. Scanned images need some preprocessing in order to be used in OCR efficiently. In this paper, we introduce a...
Conference Paper
Full-text available
Nowadays, many daily human activities such as education, commerce, talks, etc. are carried out through the Internet. In cases such as the registering in Web sites, some hackers write programs to make automatic false enrolments which waste the resources of the Web site while this may even stop the entire Web site from working. Therefore, it is neces...
Article
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...
Conference Paper
Optical Character Recognition (OCR) softwares are widely used in the office automation systems. One of the first steps in the recognition of the documents is to segment the input image. Various methods have been offered for the English language. For the Persian/Arabic Language, however, no complete method has been found yet. In this paper we presen...
Article
This paper introduces the Virtual Grade project, in which the students' grades are provided on the web with a moderate degree of security. In this method without creating a list of the information available in the database, each individual can access the necessary information if provided on the web. In our method an image is created for each data,...

Citations

... Paired comparison tests (so-called 'AB tests') exhibit a much lower variance in their responses, which in turn makes statistical significance easier to detect [2,3]. Although it is possible to retrieve ordinal rankings from AB tests [4], MOS (and to some extent MUSHRA tests [5]) are presumably more widely used as their results can directly be used to rank systems in a single scale. In a MUSHRA (MUltiple Stimuli with Hidden Reference and Anchor) test, participants are asked to score systems on a scale from 1-100 by listening to stimuli for the same text side-by-side alongside a high quality reference. ...
... Thus, in addition to the rate of packet arrivals, the idle time should be set based on the flow table capacity as well as the eviction mechanism in place. The authors in [16] show that sometimes it may be beneficial to remove a flow rule before the flow ends to reduce average flow table occupancy. ...
... Privacy and security provided by the VCED's is a major concern area for the consumers, and such concerns reflect a lower level of trust between humans and machines [2,3]. In this aspect the consumer electronics (CE) community is doing an excellent work in terms of improving the security of the devices by introducing sophisticated encryption algorithms or other advanced cybersecurity principles [4,5,6]. A lot of focus is also being given to the privacy aspects of these VCED's, by incorporating the privacy-by-design philosophy [7,8]. ...
... This section is not intended to be a comprehensive review of the whole literature. Interested readers can refer to the work in [8] for an extensive survey of the state of the art. Henceforth, we refer to a single instance of a CAPTCHA test prompted to a user with the term challenge. ...
... Human Interactive Proofs (HIPs) [1] focus on automation tests that virtually all humans can pass but current computer programs fail [2]. Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) was an acronym that was coined in 2000. ...
... In the third phase, a flow rule redistribution mechanism is proposed by detecting flow rule congestion at the switches so that new flows can be accommodated in the network. The results of the proposed mechanism are compared with existing mechanisms, such as ReWiFlow [155] and ExactMatch, and show clear improvement in network performance. The research work in [156] proposes a flow rule placement mechanism called "hybrid flow table architecture" that utilizes the advantages of hardware and software flow table implementations. ...
... Many studies pointed out possible bottlenecks at the control channel and attempted to alleviate them by distributing the control logic [19]. On the other hand, monitoring techniques such as device statistics polling [20,21] and active probing [22] also attempted to decrease the communication overhead using an adaptive polling rate [23] or probing rate [24]. However, given the coarse granularity of the monitored information, these techniques are not always able to identify network performance issues [25]. ...
... Score Total [49], [44], [11], [45], [37], [36], [73], [84], [85], [86], [88], [89], [91], [43], [39], [93], [94], [95], [97], [98], [99], [101], [103], [104], [105], [107], [108], [109], [113], [51], [56], [116], [118], [119], [120], [40], [122], [123], [125] 57% 4 [66], [42], [38], [92] 6% 3.5 [67], [70], [15], [46], [72], [90], [96], [100], [102], [50], [106], [112], [42], [114], [48], [117], [41], [121], [124] 28% 3 [115] 1% 2.5 [14], [69], [71], [87], [47] 7% 2 [68] 1% 1 packet handling. Although many applications are not specifically designed to execute the deviant behaviour, their integration with the system releases the vulnerabilities. ...
... To support system packet sampling, probabilistic packet sampling and other diverse sampling approaches in an SDN, an extended OpenFlow called FleXam was suggested in [24]. In [25], the authors suggested a low-latency, sampling-based network measurement platform called OpenSample, which implements quick traffic statistics measurement in SDN using the probabilistic packet sampling of the sFlow protocol. ...
... Lastly, Pakdel [31] and Reynaga [35] presented usability and reliability as two of the most important facts while designing a user-friendly and security-enhancing captcha. Seesay and HearSay proposed by Shirali et al. [37] introduced the techniques of receiving answers in audio format. By introducing this method, authors significantly minimized the entry of wrong input and reduced completion time. ...