To answer this question, you need to understand the concept of message integrity and the different options available to ensure it. Let's go through each option to understand why it is correct or incorrect:
Option A) Send a digital signature of the message to the recipient - This option is incorrect because a digital signature is used for message authentication, not message integrity. It ensures that the message comes from the claimed sender and has not been tampered with, but it does not specifically address message integrity.
Option B) Encrypt the message with a symmetric algorithm and send it - This option is incorrect because encryption alone does not provide message integrity. Encryption only protects the confidentiality of the message, ensuring that it cannot be read by unauthorized parties. It does not verify the integrity of the message or detect any modifications during transmission.
Option C) Encrypt the message with a private key so the recipient can decrypt with the corresponding public key - This option is incorrect because it describes asymmetric encryption, which is primarily used for confidentiality and authentication. While asymmetric encryption can provide some level of integrity, it is not the most effective option for ensuring message integrity.
Option D) Send an encrypted hash of the message along with the message to the recipient - This option is correct because it involves sending an encrypted hash (also known as a digital signature) of the message along with the message itself. By encrypting the hash, the recipient can verify the integrity of the message by comparing the decrypted hash with a recalculated hash of the received message. If the hashes match, it ensures that the message has not been tampered with during transmission.
The correct answer is D) Send an encrypted hash of the message along with the message to the recipient. This option is correct because it provides a way to verify the integrity of the message.