Security engineering is the field of engineering dealing with the security and integrity of real-world systems.
It is similar to systems engineering in that its motivation is to make a system meet requirements, but with the added dimension of enforcing a security policy.
It has existed as an informal field for centuries, in the fields of locksmithing and security printing.
Technological advances, principally in the field of computers, have now allowed the creation of far more complex systems, with new and complex security problems.
Because modern systems cut across many areas of human endeavor, security engineers not only need consider the mathematical and physical properties of systems; they also need to consider attacks on the people who use and form parts of those systems using social engineering attacks.
Secure systems have to resist not only technical attacks, but also coercion, fraud, and deception by confidence tricksters.
For this reason it involves aspects of social science, psychology and economics, as well as physics, chemistry and mathematics.
Some of the techniques used, such as fault tree analysis, are derived from safety engineering.