Data and Applications Security Developments and Directions

1. Data and Applications Security Developments and Directions Dr. Bhavani Thuraisingham The University of Texas at Dallas Lecture #11 Inference Problem - I September 24, 2010

2. Outline • History • Access Control and Inference • Inference problem in MLS/DBMS • Inference problem in emerging systems • Semantic data model applications • Confidentiality, Privacy and Trust • Directions

3. History • Statistical databases (1970s – present) • Inference problem in databases (early 1980s - present) • Inference problem in MLS/DBMS (late 1980s – present) • Unsolvability results (1990) • Logic for secure databases (1990) • Semantic data model applications (late 1980s - present) • Emerging applications (1990s – present) • Privacy (2000 – present)

4. Statistical Databases • Census Bureau has been focusing for decades on statistical inference and statistical database • Collections of data such as sums and averages may be given out but not the individual data elements • Techniques include • Perturbation where results are modified • Randomization where random samples are used to compute summaries • Techniques are being used now for privacy preserving data mining

5. Access Control and Inference • Access control in databases started with the work in System R and Ingres Projects • Access Control rules were defined for databases, relations, tuples, attributes and elements • SQL and QUEL languages were extended • GRANT and REVOKE Statements • Read access on EMP to User group A Where EMP.Salary < 30K and EMP.Dept <> Security • Query Modification: • Modify the query according to the access control rules • Retrieve all employee information where salary < 30K and Dept is not Security

6. Query Modification Algorithm • Inputs: Query, Access Control Rules • Output: Modified Query • Algorithm: • Given a query Q, examine all the access control rules relevant to the query • Introduce a Where Clause to the query that negates access to the relevant attributes in the access control rules • Example: rules are John does not have access to Salary in EMP and Budget in DEPT • Query is to join the EMP and DEPT relations on Dept # • Modify the query to Join EMP and DEPT on Dept # and project on all attributes except Salary and Budget • Output is the resulting query

7. Security Constraints / Access Control Rules • Simple Constraint: John cannot access the attribute Salary of relation EMP • Content-based constraint: If relation MISS contains information about missions in the Middle East, then John cannot access MISS • Association-based Constraint: Ship’s location and mission taken together cannot be accessed by John; individually each attribute can be accessed by John • Release constraint: After X is released Y cannot be accessed by John • Aggregate Constraint: Ten or more tuples taken together cannot be accessed by John • Dynamic Constraint: After the Mission, information about the mission can be accessed by John

8. Security Constraints for Healthcare • Simple Constraint: Only doctors can access medical records • Content-based constraint: If the patient has Aids then this information is private • Association-based Constraint: Names and medical records taken together is private • Release constraint: After medical records are released, names cannot be released • Aggregate Constraint: The collection of patients is private, individually public • Dynamic Constraint: After the patient dies, information about him becomes public

9. Inference Problem in MLS/DBMS • Inference is the process of forming conclusions from premises • If the conclusions are unauthorized, it becomes a problem • Inference problem in a multilevel environment • Aggregation problem is a special case of the inference problem - collections of data elements is Secret but the individual elements are Unclassified • Association problem: attributes A and B taken together is Secret - individually they are Unclassified

10. Revisiting Security Constraints • Simple Constraint: Mission attribute of SHIP is Secret • Content-based constraint: If relation MISSION contains information about missions in Europe, then MISSION is Secret • Association-based Constraint: Ship’s location and mission taken together is Secret; individually each attribute is Unclassified • Release constraint: After X is released Y is Secret • Aggregate Constraint: Ten or more tuples taken together is Secret • Dynamic Constraint: After the Mission, information about the mission is Unclassified • Logical Constraint: A Implies B; therefore if B is Secret then A must be at least Secret

11. Enforcement of Security Constraints User Interface Manager Constraint Manager Database Design Tool Constraints during database design operation Security Constraints Update Processor: Constraints during update operation Query Processor: Constraints during query and release operations MLS Database MLS/DBMS

12. Query Algorithms • Query is modified according to the constraints • Release database is examined as to what has been released • Query is processed and response assembled • Release database is examined to determine whether the response should be released • Result is given to the user • Portions of the query processor are trusted

13. Update Algorithms • Certain constraints are examined during update operation • Example: Content-based constraints • The security level of the data is computed • Data is entered at the appropriate level • Certain parts of the Update Processor are trusted

14. Database Design Algorithms • Certain constraints are examined during the database design time • Example: Simple, Association and Logical Constraints • Schema are assigned security levels • Database is partitioned accordingly • Example: • If Ships location and mission taken together is Secret, then SHIP (S#, Sname) is Unclassified, LOC-MISS(S#, Location, Mission) is Secret LOC(Location) is Unclassified • MISS(Mission) is Unclassified

15. Data Warehouse: Data correlating Employees With Travel patterns and Projects Users Query the Warehouse Could be any DBMS e.g., relational Oracle DBMS for Employees Sybase DBMS for Projects Informix DBMS for Travel Data Warehousing and Inference Challenge: Controlling access to the Warehouse and at the same time enforcing the access control policies enforced by the back-end Database systems Data Data Data

16. Data Mining as a Threat to Security • Data mining gives us “facts” that are not obvious to human analysts of the data • Can general trends across individuals be determined without revealing information about individuals? • Possible threats: • Combine collections of data and infer information that is private • Disease information from prescription data • Military Action from Pizza delivery to pentagon • Need to protect the associations and correlations between the data that are sensitive

17. Security Preserving Data Mining • Prevent useful results from mining • Introduce “cover stories” to give “false” results • Only make a sample of data available and that adversary is unable to come up with useful rules and predictive functions • Randomization • Introduce random values into the data or results; Challenge is to introduce random values without significantly affecting the data mining results • Give range of values for results instead of exact values • Secure Multi-party Computation • Each party knows its own inputs; encryption techniques used to compute final results

18. Inference problem for Multimedia Databases • Access Control for Text, Images, Audio and Video • Granularity of Protection • Text • John has access to Chapters 1 and 2 but not to 3 and 4 • Images • John has access to portions of the image • Access control for pixels? • Video and Audio • John has access to Frames 1000 to 2000 • Jane has access only to scenes in US • Security constraints • Association based constraints • E.g., collections of images are classified

19. Inference Control for Semantic Web • According to Tim Berners Lee, The Semantic Web supports • Machine readable and understandable web pages • Layers for the semantic web: Security cuts across all layers • Semantic web has reasoning capabilities Logic, Proof and Trust S E C U R I T Y P R I V A C Y Rules/Query Other Services RDF, Ontologies XML, XML Schemas URI, UNICODE

20. Inference Control for Semantic Web - II • Semantic web has reasoning capabilities • Based on several logics including descriptive logics • Inferencing is key to the operation of the semantic web • Need to build inference controllers that can handle different types of inferencing capability

21. Example Security-Enhanced Semantic Web Interface to the Security-Enhanced Semantic Web Technology to be developed by project Inference Engine/ Inference Controller Security Policies Ontologies Rules XML, RDF Documents Web Pages, Databases Semantic Web Engine

22. Security, Ontologies and XML • Access control for Ontologies • Who can access which parts of the Ontologies • E.g, Professor can access all patents of the department while the Secretary can access only the descriptions of the patents • Ontologies for Security Applications • Use ontologies for specifying security/privacy policies • Integrating heterogeneous policies • Access control for XML (also RDF) • Protecting entire documents, parts of documents, propagations of access control privileges; Protecting DTDs vs Document instances; Secure XML Schemas • Inference problem for XML documents • Portions of documents taken together could be sensitive, individually not sensitive

23. Semantic Model for Inference Control Dark lines/boxes contain sensitive information Cancer Influenza Has disease John’s address Patient John England address Travels frequently Use Reasoning Strategies developed for Semantic Models such as Semantic Nets and Conceptual Graphs to reason about the applications And detect potential inference violations

24. Directions • Inference problem is still being investigated • Census bureau still working on statistical databases • Need to find real world examples in the Military world • Inference problem with respect to medial records • Much of the focus is now on the Privacy problem • Privacy problem can be regarded to be a special case of the inference problem