Fundamental of Security Design Principles

Fundamental Security Design Principles

• Economy of Mechanism: Design systems as simple and small as possible to reduce opportunities for security flaws.
• Benefit: Simplified design makes it easier to test and verify security properties.
• Examples: Prefer fewer lines of code or less complex protocols in software, and fewer physical points of entry in hardware.

Fail-Safe Defaults

• Definition: The default state of a system, in the event of failure, should be secure.
• Benefit: In case of a system failure, the system remains secure and does not expose resources to unauthorized users.
• Examples: A firewall that by default blocks all traffic except that which is explicitly allowed.

Complete Mediation

• Definition: Every access to a system's resources must be checked for authority.
• Benefit: Prevents unauthorized access by ensuring that all accesses are authenticated and authorized.
• Examples: A file system that checks permissions every time a file is accessed, not just the first time.

Open Design

• Definition: A system's security should not depend on secrecy of its design or implementation.
• Benefit: Allows for widespread review by experts, which can lead to identification and correction of flaws.
• Examples: Cryptographic algorithms like AES or protocols like TLS that are open standards.

Separation of Privilege

• Definition: A practice in which multiple privilege attributes are required to achieve access to a restricted resource.
• Benefit: Reduces the risk of a single point of failure in security mechanisms.
• Examples: Multi-factor authentication that requires both a password and a physical token.

Encapsulation

• Definition: Objects encapsulate data and operations on data, providing interfaces and hiding their internal state.
• Benefit: Allows for the internal structure to be changed without affecting other system parts, which can improve security.
• Examples: Object-oriented programming where an object's data is not accessible directly, but only through its methods.

Modularity

• Definition: Software is divided into separate modules that are developed independently but operate cohesively.
• Benefit: Improves maintainability and comprehensibility, and allows for secure updates and patching of individual modules.
• Examples: Plug-in architectures where individual modules or plug-ins can be added or updated independently.

Layering

• Definition: Security is implemented in overlapping layers that provide protection even if one layer is breached.
• Benefit: Provides depth in defense, as an attacker must penetrate multiple layers to compromise a system.
• Examples: A network with firewalls, intrusion detection systems, and anti-malware technologies.

Least Astonishment

• Definition: A principle that suggests users should not be surprised by the behavior of a system.
• Benefit: Consistent and predictable system response to user actions.
• Examples: A system that provides clear and consistent error messages and feedback.