Security by design is an approach to developing and designing systems, products, or processes with security considerations incorporated from the very beginning. It involves considering security requirements and potential threats throughout the entire design and development process, rather than treating security as an afterthought or an add-on feature. 

1. The principle of Least Privilege and Separation of Duties

2. The principle of Defense-in-Depth

3. The principle of Zero Trust

4. The principle of Security-in-the-Open

These principles serve as guidelines to incorporate security into the design process and help create systems that are secure, resilient, and able to withstand evolving threats.