Certified Ethical Hacker (CEH v11) — Question 312

Bob wants to ensure that Alice can check whether his message has been tampered with. He creates a checksum of the message and encrypts it using asymmetric cryptography.
What key does Bob use to encrypt the checksum for accomplishing this goal?

Answer options

• A. Alice's public key
• B. His own public key
• C. His own private key
• D. Alice's private key

Correct answer: C

Explanation

Bob uses his own private key to encrypt the checksum, allowing Alice to verify the message's integrity with his public key. Options A and B are incorrect because encrypting with Alice's public key would not enable him to prove authenticity, and using his own public key would not provide a means for Alice to confirm the message. Option D is incorrect because Alice's private key is not involved in this process.