Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Combinatorial Methods for Software


Most security vulnerabilities arise from flaws in software implementation, and are difficult to discover because they are often triggered by rarely used parts of the code. Exhaustive testing is impossible for real-world software so high assurance software is tested using methods that require extensive staff time and thus have enormous cost. Most unit and system testing only verifies the existence of functionality, so it does not exercise rare conditions that trigger security vulnerabilities.


Reduction in the cost of security testing for US software industry.

Created December 22, 2009, Updated March 23, 2018