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An Access Control Model for Video Database SystemsAs a joint work of: Elisa Bertino1, Ahmed K. Elmagarmid 2 and Moustafa M. Hammad21Dipartimento di Scienze dell'Informazione. Universit degli Studi di Milano. Via Comelico, 39/41 20135 Milano, Italy. bertino@dsi.unimi.it. 2Computer Science Department, Purdue University. 1398 Computer Science Bld., West Lafayette IN 47907. {ake,mhammad}@cs.purdue.edu.
Introduction • Video data possess unique features that distinguished them from other data types. ( e.g. different media types - visual, audio and text-, schemaless, massive volume, time and space-variant, rich semantic contents - a picture worth 1000 words, what about video????) • Different approaches to model video data like: • Segmentation-based, physical features oriented; color histogram, textures, audio, text. • Annotation-based, semantic features oriented. Video description is used to access video. • Large amount of digital video > 1.8 M Gbytes, and a large investments, MPEG-2 has created the entirely new digital television industry worth ~30 billion $. • Hence a need to provide secure and organized access to video database !!!! or access control. • Is Access Control based on physical or semantic content? Our work is focused on access control based on video semantics to exploit the expressive power in video.
Topics of Discussion • Video data model. • Authorization model for video database. • Access control techniques. • System architecture. • Conclusion and future work.
Video Data Model Physical video segment Physical video stream Hot Object Life time interval or logical video segment John plying with his bicycle
Authorization Model • Closed system access control ( no access permission unless explicitly specified in the system). • User access requests are checked against authorization rules. • Authorization rule specification entails: • Subject Specification, • Object Specification, and • Mode Specification. Access request Authorization rules Request satisfies authorization rules Yes No Grant Deny
Subject Specification • Use of credential • Characteristic and attributes of users (user profiles) instead of only user identifiers. • Example: (Name: John, Age: 8, Job: student,……). • Suitable for video data. • Credential type (schema), credential and credential expression. • We specify a simple language for credential expressions. • Examples of credential expressions: • Student(x): representing all users that are students. • x.age < 18: denoting all users having age < 18. • Student(x) AND x.age < 18: Students with age < 18. • Credential expression is finally evaluated to a set of user identifiers. • Subject is specified as either: • list of users identifiers or credential expression.
Object Specification • We base our access model on logical video level to: • be easy to apply and modify, and • allow specification of access based on semantic video contents. • Video objects possess more than just physical characteristic (semantic contents). • Annotations describe video semantic and one can extract concepts from video annotation. (e.g. FIAT and MAZDA are CARS). • In its simplest form concepts represent just annotation keywords. • We use concepts that describe video semantics to specify video security.
Object Specification (Cont.) • Concept expression involves one or more concepts with video operators between them. Video operators are either spatial, temporal, spatio-temporal or Boolean operators. • Concept expression: • The set CPE of concept expressions is built from atoms and operation , video operation. • Atoms can be of the following types: • c , where c set of concepts. • c1 c2 , where c1, c2 are concepts and set of video operations. • Then the set CPE of concept expressions is recursively defined as follows: • Every atom is a concept expression. • If CpE1 and CpE2 are concept expressions, then CpE1 CpE1, CpE1CpE1, CpE1 , (CpE1) are also concept expressions.
Object Specification (Cont.) • Concepts expression finally evaluates to set of logical video segments that contain concepts satisfying the expression. • Examples of concept expressions: • “World War IIDigol” denotes all frame intervals that have General Digol as a hot object and deal with World War II. • “ Ortiga DURING drug trial” denotes all frame intervals that have former Colombian president Ortiga” during the drug trial in court video. • “ DISCOVERY CLOSE spying satellite” denotes all frame intervals that have DISCOVERY space shuttle fixing or close to a spying satellite in NASA video library. • Video Object can be specified either: • by providing a set of logical video elements. • by providing concept expression.
Authorized Object • Consists of two parts: • protected objects (po): which represent video elements user wants to access, and • restricted objects (ro) : which represent video elements user is restricted to access. • Authorized objects (ao) is defined as the following expression: • ao = po ro, where is defined as the exclusion of restricted object from protected ones. Protected object Restricted object = Authorized Object
Mode Specification • low level operations like (read and write) are not suitable in video access control. • More abstract level operations are used to specify different access modes: • View (annotations), View(Rframes), Play(period, quality), Edit(annotation), Edit(logical-video), Edit(Physical-video). • Those operations are in increasing power, the successor subsumes the predecessor.
Access Control Mechanism • A user submits a request to access video element, • The access control routine checks the authorization rule repository for an authorization rule satisfies : • User is one of the subjects, • The accessed object is one of the protected objects, • The operation is equal or less than the specified mode. • If not found, user is unauthorized. • Else If the object is a restricted one Then apply operator and authorize the subject to the new object. Else authorize the subject.
Conclusion and future work • Provide access control based on video semantic not only physical features. • Support for different video granularity access control. • Not a dump guard but smart manager (apply filter effects). • Provide categories of video privileges. • Use of credentials instead of just identifiers. • Providing modular access control architecture. • The model can be adapted to video models that provide content description mechanisms (MPEG-7).
Conclusion and future work (cont.) • Real time provision of access control. • Distributed implementation. • PICS (Platform for Internet Content Selection).