computer science

Software diversity

Software diversity is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Software diversity rather than just read about it. In short: Software diversity is a research field about the comprehension and engineering of diversity in the context of software. Areas The different areas of software diversity are discussed in surveys on diversity for fault-tolerance or for security.

Key takeaways

Software diversity belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Software diversity to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Software diversity from memory before moving on to harder problems.

Reference excerpt

Software diversity is a research field about the comprehension and engineering of diversity in the context of software.

Areas The different areas of software diversity are discussed in surveys on diversity for fault-tolerance or for security. The main areas are:

design diversity, n-version programming, data diversity for fault tolerance randomization software variability

Techniques

Code transformations It is possible to amplify software diversity through automated transformation processes that create synthetic diversity. A "multicompiler" is compiler embedding a diversification engine. A multi-variant execution environment (MVEE) is responsible for selecting the variant to execute and compare the output. Fred Cohen was among the very early promoters of such an approach. He proposed a series of rewriting and code reordering transformations that aim at producing massive quantities of different versions of operating systems functions. These ideas have been developed over the years and have led to the construction of integrated obfuscation schemes to protect key functions in large software systems. Another approach to increase software diversity of protection consists in adding randomness in certain core processes, such as memory loading. Randomness implies that all versions of the same program run differently from each other, which in turn creates a diversity of program behaviors. This idea was initially proposed and experimented by Stephanie Forrest and her colleagues. Recent work on automatic software diversity explores different forms of program transformations that slightly vary the behavior of programs. The goal is to evolve one program into a population of diverse programs that all provide similar services to users, but with a different code. This diversity of code enhances the protection of users against one single attack that could crash all programs at the same time. Transformation operators include:

code layout randomization: reorder functions in code globals layout randomization: reorder and pad globals stack variable randomization: reorder variables in each stack frame heap layout randomization

Natural software diversity It is known that some functionalities are available in multiple interchangeable implementations. This natural diversity can be exploited, for example it has been shown valuable to increase security in cloud systems.

References

Worked examples

Example 1 — a first encounter with Software diversity

Start with the simplest possible case. Write down what Software diversity claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Software diversity before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Software diversity ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Software diversity

In research: Software diversity appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Software diversity in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Software diversity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Software engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Software diversity outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Software diversity in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Software diversity means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Software diversity out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Software diversity in simple terms?

Software diversity is a research field about the comprehension and engineering of diversity in the context of software. Areas The different areas of software diversity are discussed in surveys on diversity for fault-tolerance or for security.

Why does Software diversity matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Software diversity?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Software diversity.