Development of Control and Confidentiality for Database Management Systems

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Early research efforts in the area of access control and confidentiality for DBMSs focused on the development of two different classes of models, based on the unrestricted access control policy and on the mandatory access control policy. This early research was transmitting in the framework of relational database systems. The relational data model, being a declarative and high-level model for specifying the logical structure of data, made the development of simple declarative languages for specifying access control policies. These earlier models and the unrestricted models in particular, introduced some important principles that set apart access control models for database systems from access control models adopted by operating systems and file systems. The primary principle was that access control models for databases should be expressed in terms of the logical data model; thus authorizations for a relational database should be expressed in terms of relations i.e. in tabular form, relation attributes, and tuples. The next principle is that for databases, in addition to name-based access control, where the protected objects are specified by specifying their names, content-based access control has to be supported. Content based access control permits the system to decide whether to provide or deny access to a data item based on the contents of the data item. The development of content based access control models, which are, in general, based on the requirement of conditions against data contents, was made easy in relational databases by the availability of declarative query languages, such as SQL. In the area of unrestricted access control models for relational database systems, an important early contribution was the development...

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...proach, the LSB of each byte of the cover file is replaced with bits from the message.
B. Injection approach. In the injection approach, the source message is hidden in sections of the cover file that are ignored by the processing application. Therefore, avoid modifying those file bits that are related to an end-user leaving the cover file perfectly usable.
(3) Substitution approach. In the substitution approach, the least significant meaningful content of the cover file is replaced with the source message in a way that causes the least amount of distortion to the cover file.
(4) Generation approach. It is different from injection and substitution; it does not require an existing cover file but generates a cover file for the sole purpose of hiding the message.
A large number of steganography algorithms have been developed utilizing the above all the four approaches.
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