Sharif Digital Repository

In this work we present a surveillance video retrieval system based on Topic Models. We’ve shown that employing Dynamic Programming improve the effectiveness of Topic Model based retrival. In the other hand proposed method has the accuracy near to the low-level features based methods. Lightweight database is the major advantageous of propsed method over the low-level features based methods. In our work storage space occupied by database decreases from 42 MB to only 0.4 MB for the mit dataset. Moreover lightweight database strikingly speeded up the retrieval process, for example retrieval process in proposed method is about 24 times faster than low-level features based systems. Furthermore in... 

When organizations prefer to outsource their data, security protection of data will be more important. Using cryptography in addition to access control techniques is a natural way for saving confidentiality of data against untrusted server. However, encryption and decryption of data result in database performance degradation. In such a situation all the information stored in encrypted form, one cannot make the selection on the database content any more. Data should be decrypted first, so an unwilling tradeoff between the security and performance is normally forced. The appropriate approaches to increase the performance are methods to deal directly with the encrypted data without firstly... 

One of the security issues in data outsourcing scenario is the enforcement of data owner’s access control policies. This includes three challenges; 1) the average number of keys needed to access authorized resources, 2) efficient update of policies, and 3) confidentiality of data owner’s access control policies. Most of the existing proposed solutions address only one of these challenges, while they impose high overhead on both the data owner and users. Such an overhead prevents the model to be implemented in practical applications. In this thesis, we propose an approach to address all the aforementioned challenges with acceptable overhead. In this approach, which is based on selective... 

Talking face synthesis is a process in which is made using audio-visual data or its features. Because the face is the first output, face animation plays a crucial role in this process. A high-quality face, a balance between different facial regions, natural movements of facial organs, and the like are basic requirements to synthesize a relatively realistic talking face. There are a wide variety of applications for the photo-realistic talking face. For instance, as a teaching assistant, or reading emails and e-books are only two simple ones to mention. To reach a realistic talking face with mentioned necessary requirements, we set a goal to consider all face regions and their movements. To... 

Compound verbs (CVs) and its components, have been widely discussed in previous linguistics' researches as one of the most important and fundamental constructions of Persian language. Nevertheless most of the arguments and assumptions in those researches align with each other and studying CVs from another aspect with a different viewpoint has not been considered very much in order to solve nodes and issues in this area. We have endeavored in this thesis to review and criticize the portrayed definitions of the CVs, reconsider this construction and the syntactical and semantical roles of verbal and non-verbal elements in this combination from another point of view, and revise the previous... 

Data outsourcing As a cloud service, it is a solution to reduce the cost of data storage and management in small and medium organizations. One of the main concerns in this area is the privacy of data owners and the non-disclosure of information by curious (albeit trusted) public cloud service providers. Resolving this issue requires encrypting the data before sending it to the cloud server. Transferring all encrypted data to the cloud server and performing various queries after encryption imposes a lot of time, computational and storage overhead, which destroys the philosophy of outsourcing. One of the open research issues is the processing of join queries over encrypted data by the cloud... 

Data outsourcing is an approach to delegate the burden of data management to external servers. In spite of its clear advantages, data outsourcing requires security assurances including data confidentiality, query result correctness, and access control enforcement. Research proposals have identified solutions with disparate assumptions for different security requirements. It is a real obstacle towards having an integrated solution through the combination of existing approaches. The practicality of data outsourcing to the cloud is seriously affected by this challenge. In this thesis, a unified view based on secret sharing is proposed to simultaneously achieve confidentiality, correctness, and... 

In the secure data outsourcing scenario, verification of the reply of an unreliable server includes assessing the authenticity, completeness and it’s integrity. In this thesis, an efficient method, with emphasis on freshness, has been introduced to evaluate the correctness of the replies from a server. It takes in hand different application needs, inherent differences in the data, and different update mechanisms. This method evaluates freshness by using timestamps alongside the data being out sourced. Due to the requirement of verifying not only the freshness of the response, but the correctness of the timestamps as well, two general methods for evaluating and verifying the responses were... 

An important class of applications which have been rapidly growing recently is the one that create and use time series data. These types of data sets are ordered based on the timestamps associated to their data items. In practice, traditional relational databases are unable to satisfy the requirements of these data sets; however, NoSQL databases with column-wide data structure are appropriate infrastructure for them. These databases are very efficient in read and write operations (especially for time series data, which are ordered) and are able to store unstructured data. Time series data may contain valuable and sensitive information; hence, they should be protected from the information... 

Nowadays large volume of sensitive data of organizations are stored in the databases. Thus, databases are attractive to the attackers to execute different types of attacks with different purposes. The useful information that attackers try to achieve in the preliminary steps of the attacks against the databases, is the database structure or schema. One of the popular approach to extract the schema of a database is to analyze the returned error messages from its DBMS. Hence, a solution to prevent schema disclosure via the error messages is customizing and modifying them. To achieve this goal, in this thesis, we propose a framework to handle and customize the error messages automatically and... 

In recent years, there has been a trend toward outsourcing data to the cloud provider. These companies must tackle the data security challenges. Generally these parties are assumed to be honest but curious. In past years, the research communities have been investigating different solution to ensure confidentiality.
In addition to data confidentiality access and pattern confidentiality is a high-priority issue in some cases so. potential adversary should be unable to drive information from the observed access pattern to the outsourced data. Despite the fact that there are more investigation in the field of data confidentiality, concern over data security are the rise in outsourcing data,... 

The ever-increasing volume of data and the lack of computational and storage facilities have caused a managerial challenge to organizations. The existence of these challenges on the one hand and the increase of storage services on the other hand have compelled the organizations to delegate their storage and management of data to the server providers of cloud storage services. The outsourcing of data to servers obviates the need for purchasing exorbitant storage equipment and recruiting professional workforce in the organization. Since the organization’s data will be kept outside the organization’s ambience in case of using such services in form of outsourcing, and the data will not be under... 

Using database encryption to protect data in some situations where access control is not soleley enough is inevitable. Database encryption provides an additional layer of protecton to conventional access control techniques. It prevents unauthorized users, including intruders breaking into a network, from viewing the sensitive data. As a result data remains protected even in the event that database is successfully attacked or stolen. However, encryption and decryption of data result in database performance degradation. In the situation where all the information is stored in encrypted form, one cannot make the selection on the database content any more. Data should be decrypted first, so an... 

With the growing use of computer systems, especially in form of web applications, software development and customer requirements has become more complex. Modern computer systems are supposed to achieve non-functional requirements in addition to functional requirements. Non-functional requirements are also called software quality attributes. One of the most important quality attributes for today's software systems is performance. Today’s softwares due to the growing number of their users, need more efficiency than ever to properly meet the performance request.Storage components and databases are the most important factors in causing performance bottlenecks in web applications. Most of... 

Simulation of biological behaviors as the pre requirement for control and optimization, especially for recognition and treating diseases, requires studying involved reactions which may or may not be accessible. In the other side, finding the correct network structures and related mathematical expressions to simulate biological behaviors is a complicated problem due to multi aspect interactions among biological reactions, which imply an approach that integrate the knowledge coming from multiple discipline including biological concepts, mathematical modelling, bioinformatics and advanced programming. In this study we aim to analyze this problem using ontological inference to develop a... 

Recently, many organizations outsource their data on an external server to rescue the trouble of data maintenance. But, data owners do not trust in the external server to enforce defined access control policies. In recent years, many researches was dedicated to cryptographic access control on outsourced data, in order to solve this problem. We introduce a method based on Attribute-based Encryption to enforce access control on outsourced data. In this method we consider policy updating and administrative access control. As a result The owner is not only able to change access control policies on outsourced data but also to define administrative rights (grant/revoke) for some admin users. Our... 

Extensive studies have been performed on the genetic variations involved in common neurodegenerative diseases such as Alzheimer's, macular degeneration, and Parkinson's. In most cases, no specific gene has been identified pointing to a distinct pathogenic pathway, therefore, this study mainly aims to find common genes among aforementioned diseases according to determination of a specific pathogenic protein pathway.In this study, we reached a deep understanding of the function of nervous system and the discovery of causative agents of the diseases by applying the sources of information from genome datasets in bioinformatics analysis. The utilized database comprises the classification of... 

Data outsourcing provides cost-saving and availability guarantees. However, privacy and confidentiality issues, disappoint owners from outsourcing their data. Although solutions such as CryptDB and SDB tried to provide secure and practical systems, their enforced limitations, made them useless in practice. Inability in search on encrypted data, is one of the most important existing challenges in such systems. Furthermore, the overhead of mechanisms such as FHEs, removes them from considering for any practical system. Indeed, special purpose encryptions would be the only usable mechanisms for such purposes. However, their limited functionality does not support some important required... 

With increasing use of computers in everyday life, improved communication between machines and human is needed. To make a right communication and understand a humankind face which is made in a graphical environment, implementing the audio and visual projects like lip reading, audio and visual speech recognition and lip modelling needed. The main goal in this project is natural representation of strings of lip movements for Farsi language. Lack of a complete audio and visual database for this application in Farsi language made us provide a new complete Farsi database for this project that is called SFAVD. It is a unique audio and visual database which covers the most applicable words, all... 

One of the security issues in database outsourcing scenario is the correctness of the query results. Correctness verification includes integrity, completeness and freshness of the results. Most of the proposed approaches for correctness verification impose high overhead on the components of the scenario which prevents the scenario to implemented in practical applications. In this thesis, we have proposed a probabilistic approach which imposes acceptable overhead for correctness verification of returned results of service provider. The approach uses the previous behavior of the service provider to calculate a trust value toward it which is used to adjust the imposed overhead. In other words,...