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# System prepended metadata

title: Usable Privacy and Security

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# 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
    - ![](https://i.imgur.com/kcTScB5.png)
- Memorability
    - ![](https://i.imgur.com/CS6ZIpv.png)
- 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 ![](https://i.imgur.com/X1x5rzn.png)
- 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