📌 Message Authentication Codes Summary

Message Authentication Codes, or MACs, are short pieces of information used to check that a message really comes from the sender and has not been changed along the way. They use a secret key shared between the sender and receiver to create a unique code for each message. If even a small part of the message changes, the MAC will not match, alerting the receiver to tampering or errors.

🙋🏻‍♂️ Explain Message Authentication Codes Simply

Imagine sending a letter with a special stamp that only you and your friend know how to make. If someone tries to copy or change the letter, they will not be able to make the correct stamp. When your friend sees the stamp is correct, they know the letter is from you and was not changed.

📅 How Can it be used?

You could use a MAC to ensure only authorised users can send valid requests to an online banking API.

🗺️ Real World Examples

Online payment systems often use Message Authentication Codes to confirm that payment instructions have not been altered during transmission. When a user makes a transaction, the system generates a MAC with a secret key and attaches it to the payment request. The receiving bank verifies the MAC before processing the transaction, helping to prevent fraud.

Software update services use MACs to protect update files. Before downloading and installing an update, the software checks the MAC to confirm the update file is genuine and has not been tampered with by attackers.

✅ FAQ

A Message Authentication Code, or MAC, is like a digital seal that proves a message really comes from who you think it does and that it has not been tampered with. It uses a secret key shared by the sender and receiver to create a code for each message. If the message changes, the code will not match, so you know something is wrong. This is important for keeping information safe when it is sent over the internet or other networks.

A MAC checks that a message has not been changed on its way to you and that it really comes from the person you expect. Both the sender and receiver know a secret key, and only someone with this key can make or check the code. If someone tries to change the message, the MAC will not match, so you will know not to trust it.

No, without the secret key it is nearly impossible to create a valid Message Authentication Code for a message. This is what makes MACs so reliable. Only people who know the secret key can make or check the code, so if the MAC does not match, you can be sure the message was changed or sent by someone else.

📚 Categories

• Cryptographic Primitives
• Cybersecurity
• InfoSec

🔗 External Reference Links

Message Authentication Codes link

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