Security systems engineering 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 than before, 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, as well as physics, chemistry and mathematics, it involves aspects of social science, psychology and economics. Some of the techniques used, such as fault tree analysis, are derived from safety engineering.
Other techniques such as cryptography were previously restricted to military applications.
One of the pioneers of security engineering as a formal field of study is Ross Anderson.
Sub-fields of security engineering: