[NOISE] Let's start by learning what human-computer interaction is. Human-computer interaction, which we commonly abbreviate as HCI is the study of how people interact with technology. Those people can be your average user working with a desktop or laptop computer, but they can also be people on the move using mobile devices, like, smart phones, and tablets, or even people using sensors, like, a fit bit to measure how they interact with the world. In HCI we want to understand the people, the technology, and the two fit together. From the people perspective, we want to understand both the psychological and cognitive abilities of users. This allows us to build technology that takes advantage of people's inherent abilities and also that avoid over taxing people by requiring them to do things that they're not cognitively capable of, or that are difficult. On the technology side, HCI speaks to both design and evaluation of technology. We use what we know about people, the tasks, and the way they're interacting with systems to design technology that will work well for them and we also evaluate how well that technology works to make sure we've done it right. Overall, our goal is to make sure that people aren't working any harder than necessary to use the technology that we've designed. So we start off wanting to understand users tasks in the context in which people are performing those tasks in a system. The users can be anyone from children up to elderly adults and it can be people working alone or working in teams, whether it's pairs or large groups. The tasks are things that people are trying to accomplish with the system, and can be something as easy as logging in, to something as complex as analyzing a large data set. Tasks are not necessarily intuitive to understand and we'll have a whole segment dedicated to building a list of tasks for users and finally we want to understand context. Even if we have the same users and same tasks, how they're performing those and where they're doing them can dramatically affect the systems we build. For example if we have a soldier trying to secure a system, it makes a big difference if he's doing that in an office environment or if he's out working in the field. Once we understand users tasks in context then we move into design. This is where we're building technology that consider everything we know about people and what they want to do. And hopefully we're going a build a system that makes it as easy as possible for people to accomplish those tasks. Finally, there's an evaluation step and in looking at usable security, this is not evaluation of the system security but evaluation of how easy it is for people to use that system. If it's too difficult for people, they'll simply find ways around the security, or make insecure decisions. So we want to evaluate our systems, to make sure that they're easy for people to use. This is how HCI applies to usable security and we'll now start looking at some more detailed elements of HCI and what it can help us understand.
