Design for Security
06: Security design
A commercial software company is keen to enter into the mobile application
business. For this purpose, they have come up with the concept app kids in
focus: an application which, initially, is aimed at alleviating the boredom of
children during long car journeys. In short, kids in focus allows children to
interact and play games, via a 3G enabled tablet or smartphone, with their
grandparents (over a tablet, smartphone or PC).
Whilst the application will be running on smartphones and tablet devices,
parts of the service will be supported by the company’s own online
service. Once the children’s and the grandparent’s devices have been registered
with this online service, a connection can be initiated between the two
devices, enabling audio and video chat (depending on available bandwidth),
and allowing the children to play a variety of games with their grandparents.
The software company is keen to make sure that a good selection
of games can be supported as they envisage this to be the main revenue
stream through the purchase of new games, either by the parent or the
grandparent. Additionally, it is proposed that details of the car’s location
be made available to the grandparents, in order to keep them informed of
the journey’s progression.
The company is very keen for the system to be easy to use and to operate
securely. They have contracted you to provide a security analysis and highlevel
design for this system.
The following is a simple use case diagram that illustrates what the new
system should do.
Question 1 (Stakeholders) Identify all the important stakeholders in such
a system. Throughout the rest of the exercise you should pay particular
attention to the needs of each of these stakeholders.
Question 2 (Assets and security properties) Identify the most significant
assets in the system and their security properties. Think about the context in
which these operate. Are there any specific usability design considerations
that you might want highlight?
Question 3 (Risks) Briefly identify what you think are the most significant
risks affecting this system. For each stakeholder group you might try to identify
the most significant threats and vulnerabilities. You should feel free to
use misuse cases to structure your analysis.
1
2
Question 4 (Requirements specification) Based on your analysis so far, specify
the high level security requirements of the system such that the most important
assets are protected and the most serious risks are mitigated.
Question 5 (Design) Propose a system architecture that satisfies the requirements
you have specified.
Question 6 (Cost and benefit) Provide an argument about the cost-effectiveness
of your design? Is the security you propose good value? Are there any residual
risks that are not addressed by your design?
Child Grandparent
Register
online
Use voice chat
Play game
Buy new
game
Use video
chat
Initiate
connection
Parent
Update
location
