Bruce Schneier is an internationally-renowned security technologist and author. In this video he explores several angles on the concept "security": a feeling, a reality and (later in the video) a model. "You can feel secure, even if you are not. And you can be secure, even if you don't feel it. (...) If you look at security from an economic point, it is a trade-off. (...) time, convenience, capabilities, maybe fundamental liberties."