How does a digital signature confirm the integrity of a message?

• A. By encrypting the message with a public key
• B. By hashing the message and encrypting the hash with a private key
• C. By verifying the sender's identity
• D. By creating a unique encryption key for each message

Answer: (B)

A digital signature confirms the integrity of a message by hashing the message and then encrypting that hash with the sender's private key. This process creates a unique signature that corresponds to the message content. When the recipient receives the message, they can use the sender's public key to decrypt the hash. By generating a new hash from the original message and comparing it to the decrypted hash, the recipient can verify whether the message has been altered in transit. If both hashes match, it confirms that the message has not been tampered with and maintains its integrity. This way, the digital signature not only provides assurance of the message's integrity but also authenticates the sender, as only the sender’s private key could produce that particular hash signature.