Which procedure verifies the authenticity of messages received or stored?

• A. Encryption
• B. Message authentication
• C. Data integrity check
• D. Hashing

Answer: (B)

The procedure that verifies the authenticity of messages received or stored is message authentication. This process involves confirming that a message comes from a legitimate source and has not been altered during transmission. Message authentication typically employs techniques such as message authentication codes (MACs) or digital signatures to achieve this objective.

When a message is sent, a unique code is generated based on both the message content and a secret key; this code is transmitted along with the message. Upon receipt, the receiver can generate their own code using the same approach and compare it to the received code. If both codes match, it verifies that the message hasn’t been tampered with and is indeed from the claimed sender, ensuring authenticity.

Other options contribute to data security but serve different purposes. For example, encryption protects the confidentiality of the data by transforming it into an unreadable format for unauthorized users. Data integrity checks focus on ensuring that the data has not been corrupted or altered, typically without confirming the sender's identity. Hashing is primarily used for creating a fixed-size representation of the data, ensuring that even the slightest change in the original data results in a completely different hash value, but does not authenticate the source of the data itself.