Question

Consider the principle of complete mediation. Which non-functional system requirement will likely be affected by adhering strictly to this principle?

Short answer

The non-functional system requirement likely affected is performance.

Step-by-step solution

Understand the Principle of Complete Mediation

The principle of complete mediation requires that every access to a system resource should be checked for authorization. This means that each time a resource (like files or data) is accessed, the access permissions must be verified.

Identify System Requirements

A system has many non-functional requirements, such as performance, usability, reliability, security, and maintainability. To solve this problem, we need to determine which of these is most likely affected when strictly adhering to the principle of complete mediation.

Analyze the Impact on Performance

Checking access permissions for every access to a system resource adds computational overhead. This overhead can lead to increased response times and slower system performance, as each resource access has an additional check.

Consider the Security Improvement

While the complete mediation principle enhances security by ensuring that unauthorized accesses are prevented, this does not adversely affect the security requirements themselves. Instead, it fulfills the security objective.

Assess Usability and Maintainability

The increase in security checks due to complete mediation does not directly affect usability, since it operates at the system level, nor does it directly impact maintainability, as it does not alter how the system's components need to be updated or fixed.

Conclusion on the Affected Requirement

Considering all these factors, the non-functional requirement that is likely most affected by adhering strictly to the principle of complete mediation is performance. This is because of the additional processing required to check permissions for each access, which can slow down the system.

Key concepts

Principle of Complete Mediation

The Principle of Complete Mediation in computer security is a very important rule. It demands that every access to every resource must be authorized. Whenever a user tries to access any system resource, like file or data, the system should verify permission. This means every time without exception. This helps in preventing unauthorized access, which is crucial for maintaining security.
However, this constant checking can have some effects on other parts of the system, especially those concerning performance. Understanding and implementing this principle requires balancing security with system efficiency.

Non-Functional Requirements

Non-functional requirements define system attributes like performance, reliability, and usability. They outline how a system performs under certain conditions rather than what the system does. This is different from functional requirements, which describe specific behaviors or functions of the system.
Some of the most typical non-functional requirements include:

• Performance: How fast the system responds under a workload.
• Security: Protecting data and functionalities from threats.
• Usability: Ease of use for users.
• Reliability: Consistently performing the intended functions.
• Maintainability: Ease of updating or fixing the system.

Applying the principle of complete mediation mainly impacts performance among these non-functional requirements due to the overhead of constant security checks.

System Performance

System Performance refers to how well a computer system can process tasks. It evaluates speed, efficiency, and overall effectiveness. Whenever access control checks are added, like with the principle of complete mediation, it can affect performance by slowing it down.

Here are some factors that often impact system performance:

• Response Time: The time it takes for a system to respond to an input.
• Throughput: The amount of processing done in a given time.
• System Load: How many processes run simultaneously.

By requiring access checks every time a resource is accessed, complete mediation increases the computational load. This can lead to longer response times, reducing throughput and increasing the system load.

Access Control

Access Control is a vital component of computer security. It ensures that only authorized users have access to certain data and resources. This is implemented through policies managed by the system.

There are different models to achieve access control, such as:

• Discretionary Access Control (DAC): Users own their own data and set access permissions.
• Mandatory Access Control (MAC): Access is dictated by a central authority based on sensitivity levels.
• Role-Based Access Control (RBAC): Access is determined by the user's role within the organization.

With complete mediation, every access is controlled and checked, ensuring adherence to these models and preventing unauthorized access, which increases data security.