Page 89 - DCAP516_COMPUTER_SECURITY

Unit 7: Designing Trusted Operating System

possible – it is very difficult), and formal validation by an outside vendor. The author of these Notes
notes had been part of a software V&V (verification and validation) team, assigned to be sure
that the code was written correctly and that it adhered to the requirements.
It is based on factors such as:
1. Software architecture : E.g., kernelized design,
2. Development process : Who developed it

3. Technical assessment
There are various methods for providing assurance in operating system. These have been
discussed briefly below:

1. Testing: Testing method can demonstrate existence of flaw, not absence
2. Formal Specification and Verification: It is a time-consuming, painstaking process
3. Validation Process: This process involves requirements checking, design and code reviews,
module and system testing
4. Configuration Management and Trusted System Distribution: It improve assurance in the
development/deployment cycle.

7.7.1 Assurance Criteria

Assurance criteria are specified to enable evaluation. It was originally motivated by military
applications, but now is much wider.

Examples:
1. Orange Book (Trusted Computer System Evaluation Criteria)
2. Common Criteria

Trusted Computer System Evaluation Criteria (TCSEC)

It is a United States Government Department of Defense (DoD) standard that sets basic
requirements for assessing the effectiveness of computer security controls built into a computer
system. The TCSEC was used to evaluate, classify and select computer systems being considered
for the processing, storage and retrieval of sensitive or classified information.
The TCSEC, frequently referred to as the Orange Book, is the centerpiece of the DoD Rainbow
Series publications. Initially issued in 1983 by the National Computer Security Center (NCSC),
an arm of the National Security Agency, and then updated in 1985, TCSEC was replaced by the
Common Criteria international standard originally published in 2005.

Fundamental Objectives and Requirements

The Orange Book or DoDD 5200.28-STD was canceled by DoDD 8500.1 on October 24, 2002.

Policy

The security policy must be explicit, well-defined and enforced by the computer system. There
are two basic security policies:

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