# Usable Privacy and Security
## Measuring usability
- Speed
- How fast a task is completed when doing it optimally(ignore mistakes)
- Efficiency
- How many mistakes made when accomplishing the task
- Learnability
- 
- Memorability
- 
- User preference

## Tasks
- Login to Facebook
- Unlock phone
- Checking bank balance
### Common errors for task creation
- Leading or too descriptive
- tasks should be high-level objectives
- Specific questions
- e.g., What is the 3rd headline of this website?
- Directing users to things you want to tell them, not what they wnat to know.
- What are the names of the security team?
### Compare task between systems
- Task: give people access to a file
- command line v.s. graphical interface
- Command line
- The usability might be high for experts, but low for common people
- Graphical interface
- The reverse
> Task are goals users have when interacting with a system

> To evaluate the usability of a systemm we can create a representative list of tasks, and evaluate the usability of those tasks

## Memory
### Working memory
- short term memory
### Chunking
= "aspdoicfj" is harder to remember than "ilovecake"

## Mental model
### Labels
### Affordances
- Mapping
- Stove example 
- Visibility
- Feedback
- Grey out a button if the option is not available
### Constraints
- Fool-proof
- Only allow submit to be pressed when password is non-empty
### Conventions
- The traffic colors red-yellow-green
- thumbs-up, thumbs-down