computer science

Message authentication

Message authentication 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 Message authentication rather than just read about it. In short: In information security, message authentication or data origin authentication is a property that a message has not been modified while in transit (data integrity) and that the receiving party can verify the source of the message. Description Message authentication or data origin authentication is an information security property that indicates that a message has not been modified while in transit (data integrity) an…

Key takeaways

Message authentication 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 Message authentication to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Message authentication from memory before moving on to harder problems.

Reference excerpt

In information security, message authentication or data origin authentication is a property that a message has not been modified while in transit (data integrity) and that the receiving party can verify the source of the message.

Description Message authentication or data origin authentication is an information security property that indicates that a message has not been modified while in transit (data integrity) and that the receiving party can verify the source of the message. Message authentication does not necessarily include the property of non-repudiation.

Techniques Message authentication is typically achieved by using message authentication codes (MACs), authenticated encryption (AE), or digital signatures. The message authentication code, also known as digital authenticator, is used as an integrity check based on a secret key shared by two parties to authenticate information transmitted between them. It is based on using a cryptographic hash or symmetric encryption algorithm. The authentication key is only shared by exactly two parties (e.g. communicating devices), and the authentication will fail in the existence of a third party possessing the key since the algorithm will no longer be able to detect forgeries (i.e. to be able to validate the unique source of the message). In addition, the key must also be randomly generated to avoid its recovery through brute-force searches and related-key attacks designed to identify it from the messages transiting the medium. Some cryptographers distinguish between "message authentication without secrecy" systems – which allow the intended receiver to verify the source of the message, but they don't bother hiding the plaintext contents of the message – from authenticated encryption systems. Some cryptographers have researched subliminal channel systems that send messages that appear to use a "message authentication without secrecy" system, but in fact also transmit a secret message.

Related concepts Data origin authentication and non-repudiation have been also studied in the framework of quantum cryptography.

See also Data integrity Authentication Deniable authentication

References

Worked examples

Example 1 — a first encounter with Message authentication

Start with the simplest possible case. Write down what Message authentication 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 Message authentication 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 Message authentication 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 Message authentication

In research: Message authentication 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 Message authentication 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: Message authentication is common in secondary-school and first-year university syllabi. It links to neighbouring topics Error detection and correction, Theory of cryptography, so understanding it makes those chapters shorter.
In everyday life: Look for Message authentication 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Message authentication in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Message authentication 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 Message authentication out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Message authentication in simple terms?

Why does Message authentication 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 Message authentication?

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 Message authentication.