Message authentication is the process of verifying that a message has not been altered and originates from a legitimate source.
Thank you for reading this post, don't forget to subscribe!- It ensures that the data remains unchanged during transmission and that the sender is authentic.
- This process is essential for secure communication, particularly in environments where data is transmitted over untrusted networks (e.g., the internet).
- It assures that data received are exactly as sent (i.e., there is no modification, insertion, deletion, or replay).
Key Components of Message Authentication:
1.) Message:
The message is the original digital data that needs to be authenticated. It can be any form of digital content such as a file, email, database entry, or transaction record.
- Ensuring message integrity is crucial to prevent unauthorized modifications.
2.) Authentication Algorithm:
An authentication algorithm is a cryptographic function that generates a unique authentication code, known as a Message Authentication Code (MAC), based on the message and a shared secret key..
- Examples of authentication algorithms include HMAC (Hash-Based Message Authentication Code) and CMAC (Cipher-Based Message Authentication Code).
- It ensures that even a slight change in the message will produce a completely different MAC, helping detect tampering.
3.) Shared Secret Key:
The shared secret key is a confidential value known only to the sender and the intended recipient.
- It ensures that only the authorized recipient can validate the message’s authenticity.
- If an attacker does not know the shared key, they cannot forge a valid MAC.
Security Objectives of Message Authentication:
1.) Message Integrity:
- It ensures that the content of the message has not been altered, tampered with, or corrupted during transmission. It helps protect against man-in-the-middle (MITM) attacks where an attacker intercepts and modifies a message.
- Example: If Alice sends a bank transaction request to Bob, message integrity ensures that the request is not altered to change the amount.
2.) Message Origin Authentication:
- It verifies that the message was genuinely sent by the expected source and not by an impersonator. This helps prevent spoofing attacks, where an attacker pretends to be a trusted sender.
- Example: If you receive an email from your bank, origin authentication confirms that the email truly originated from your bank and not from a phishing attacker.
3.) Non-Repudiation:
- It ensures that the sender of a message cannot later deny having sent it. This is typically achieved using digital signatures, where the sender signs the message using their private key. This allows the recipient (and third parties, if needed) to verify the sender’s identity.
- Example: If Alice signs a contract digitally and sends it to Bob, she cannot later claim that she never sent or agreed to the contract.
Methods of Message Authentication:
To achieve message authentication, various cryptographic techniques are used.
The most common methods include:
- Message Authentication Codes (MACs)
- Digital Signatures
- Hash Functions
1.) Message Authentication Code (MAC):
- A Message Authentication Code (MAC) is a small block of data attached to a message that ensures message integrity and authenticity using a secret key.
2.) Digital Signatures:
- A digital signature is a cryptographic technique that provides message authentication, integrity, and non-repudiation using public-key cryptography.
3.) Hash Functions:
- A cryptographic hash function is a mathematical function that converts an input message into a fixed-length digest (hash).
- The hash is unique to the input data, meaning any slight modification to the input will result in a completely different hash.