Main Types of security:

1
Database Security and Authorization
By Yazmin Escoto Rodriguez Christine Tannuwidjaja
2
Main Types of Security

• Enforce security of portions of a database
  against unauthorized access
• - Database Security and Authorization Subsystem
• Prevent unauthorized persons from accessing the
  system itself
• - Access Control
• Control the access to statistical databases
• - Statistical Database Security
• Protect sensitive data that is being transmitted
  via some type of communications
• - Data Encryption

3
Database Security and Authorization Subsystem

• Discretionary Security Mechanisms
• - concerned with defining, modeling, and
  enforcing access to information
• Mandatory Security Mechanisms for Multilevel
  Security
• - requires that data items and users are
  assigned to certain security labels

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Mandatory Access Control

• Elements
• OBJECTS
  CLASSIFICATIONS
• 
  --class(o)--
• SUBJECTS CLEARANCE
• 
  --clear(s)--
• Levels Top Secret, Secret,
  Confidential, Unclassified

5
Mandatory Access Control

• Rules
• Simple Property subject s is allowed to read
  data item d if clear(s) class(d)
• -property
• subject s is allowed to write data item d if
  clear(s) class(d)

• Simple Property protects information from
  unauthorized access
• -property protects data from contamination or
  unauthorized modification

6
Multilevel Security Databases- example

• Set up
• we have - subject x
  with clear(x) TS
• -
  subject y with clear(y) S
• -
  subject z with clear(z) U

7
Multilevel Security Databases- example
8
Multilevel Security Databases- example
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Multilevel Security Databases- example

• subject z wants to insert the next tuple
• lt Silver, LP, Omahagt

Polyinstantiation the existence of multiple
data objects with the same key
10
Multilevel Security Databases- example

• subject z wants to replace the null values with
  certain data items
• lt Markov Chain, New Jerseygt

11
Security Relevant Knowledge
Data Flow Diagram -- represents the functions the
system should perform
Entity Relationship -- describes the structural
part of the database

• Classification Constraints
• To assign to security classifications concepts of
  schemas
• ones that classify items
• ones that classify query results

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System Object
In security it is the target of protection

• Entity type
• Specialization type
• Relationship type

What is it?
O(A1..,An) - Ai (i1..N) is an attribute and is
defined over domain Di
Has an identity property (key attributes) A ?
(A1,..,An)
Notation
13
Multilevel Secure Application
MAJOR QUESTION Which way should the attributes
and occurrences of O be assigned to proper
security classifications?
CLASSIFICATION
RESULT
Security object O ? multilevel security object Om
Performed by means of security constraints
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Graphical Extensions to the ER
Secrecy Levels Ranges of Secrecy
Levels Aggregation leading to TS
(N..constant) Inference leading to
Co Evaluation of predicate P Security
dependency
(U)
(Co)
(S)
(TS)
U..S
Co..TS
N
X
P
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ER Diagram
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
Dep
Client
Salary
Title
SSN
16
Object Classification Constraints Simple
Constraints

• Let X be a set of attributes of security object O
  (X ? A1,,An)
• SiC (O(X))C, (C ? SL)
• Results in a multilevel object Om(A1, C1,, An,
  Cn,TC) where CiC ? Ai ? X, Ci left unchanged for
  Ai ? X
• Application to ER
• - SiC(Is Assigned to,Function,S)
• - assigns property Function of relationship
  Is Assigned to to a classification of secret.

17
ER Diagram classifying properties of security
objects
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
Dep
Client
Salary
Title
SSN
18
Object Classification Constraints Content-based
Constraints

• Let Ai be an attribute of security object O with
  domain Di, let P be a predicate defined on Ai and
  let X ? Ai,,An
• CbC (O(X), P Ai ? a) C or CbC (O(X), P Ai ?
  Aj) C
• (? ? ,?,lt,gt,,, a ? Di, i ? j, C ? SL)
• For any instance o of security object O(A1,,An)
  for which a predicate evaluates into true the
  transformation into o(a1,c1,,an,cn,tc) is
  performed
• Classifications are assigned in a way that ci C
  in the case Ai ? X, ci left unchanged otherwise
• Application to ER
• - CbC (Employee, SSN, Name, Salary, ,
  100, Co))
• - represents the semantic that properties
  SSN and Name of employees with a salary 100 are
  treated as confidential information

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ER Diagram classifying properties of security
objects
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
P
Dep
Client
Salary
Title
SSN
20
Object Classification Constraints Complex
Constraints

• Let O, O be two security objects and the
  existence of an instance o of O is dependent on
  the existence of a corresponding occurrence o of
  O where the k values of the identifying property
  K of o are identical to k values of attributes
  of o (foreign key)
• Let P(O) be a valid predicate defined on o and
  let X ? A1,,An be an attribute set of O
• CoC (O(X), P(O)) C (C ? SL)
• For every instance o of security object
  O(A1,,An) for which a predicate evaluates into
  true in the related object o of O the
  transformation into o(a1,c1,,an,cn,tc) is
  performed
• Classifications are assigned in a way that ci C
  in the case Ai ? X, ci left unchanged otherwise

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Object Classification Constraints Complex
Constraints (cont)

• Application to ER
• - CoC (Is Assigned to, SSN, Project,
  Subject, , Research, S)
• - individual assignment data (SSN) is
  regarded as secret information in the case the
  assignment refers to a project with Subject
  Research

22
ER Diagram classifying properties of security
objects
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
P
Dep
Client
Salary
Title
SSN
P
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Object Classification Constraints Level-based
Constraints

• Let level (Ai) be a function that returns the
  classification ci of the value of attribute Ai in
  object o(a1,c1,,an,cn,tc) of a multilevel
  security object Om
• Let X be a set of attributes of Om such that X ?
  A1,,An
• LbC (O(X)) level (Ai)
• Result for every object o(a1,c1,,an,cn,tc) to
  the assignment cj ci in the case Aj ? X
• Application to ER
• - LbC (Project, Client, Subject)
• - states that property Client of security
  object Project must always have the same
  classification as the property Subject of the
  Project

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ER Diagram classifying properties of security
objects
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
P
Dep
Client
Salary
Title
SSN
P
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Query Result Classification Constraints
Association-based Constraints

• Let O (A1,An) be a security object with
  identifying property K
• Let X (X ? A1,,An (K ? X ) be a set of
  attributes of O
• AbC (O (K,X)) C (C ? SL)
• Results in the assignment of security level C to
  the retrieval result of each query that takes X
  together with identifying property K
• Application to ER
• - AbC (Employee, Salary, Co)
• - the salary of an individual person is
  confidential
• - the value of salaries without the
  information which employee gets what salary is
  unclassified

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ER Diagram classifying query results
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
Dep
Client
Co
Salary
Title
SSN
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Query Result Classification Constraints
Aggregation Constraints

• Let count(O) be a function that returns the
  number of instances referenced by a particular
  query and belonging to security object O
  (A1,,An)
• Let X (X ? A1,,An) be sensitive attributes of
  O
• AgC (O, (X, count(O) gt n C (C ? SL, n ? N)
• Result into the classification C for the
  retrieval result of a query in the case count(O)
  gt n, i.e. the number of instances of O referenced
  by a query accessing properties X exceeds the
  value n

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Query Result Classification Constraints
Aggregation Constraints (cont)

• Application to ER
• - AgC (Is Assigned to, Title, 3, S)
• - the information which employee is assigned
  to what projects is regarded as unclassified
• - aggregating all assignments for a certain
  project and thereby inferring which team is
  responsible for what project is considered secret

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ER Diagram classifying query results
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
Dep
Client
Co
Salary
Title
SSN
3
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Query Result Classification Constraints
Inference Constraints

• Let PO be the set of multilevel objects involved
  in a potential logical inference
• Let O, O be two particular objects from PO with
  corresponding multilevel representation O
  (A1,C1,,An,Cn,TC) and
  O (A1,C1,,An,Cn,TC)
• Let X ? A1,,An and Y ? A1,,An)
• IfC (O(X), O(Y)) C
• Results into the assignment of security level C
  to the retrieval result of each query that takes
  Y together with the properties in X

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Query Result Classification Constraints
Inference Constraints (cont)

• Application to ER
• - IfC (Employee, Dep, Project, Subject,
  Co)
• - consider the situation where the
  information which employee is assigned to what
  projects is considered as confidential
• - from having access to the department an
  employee works for and to the subject of a
  project, users may infer which department may be
  responsible for the project and thus may conclude
  which employee are involved

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ER Diagram classifying query results
SSN
Function
Date
Title
Name
Is Assigned to
Subject
Employee
Project
(0,N)
(0,M)
Dep
Client
Co
Salary
Title
SSN
3
X
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QUESTION?