Certified Ethical Hacker CEH · Free Practice Question Medium
Question 97
- A Jack can be sure a message is from Jill by using her public key to decrypt the digital signature.
- B Jack can be sure a message is from Jill by using her private key to decrypt the digital signature.
- C Jack can be sure a message came from Jill by using his public key to decrypt it.
- D Jack can be sure a message came from Jill by using his private key to decrypt it.
Reveal correct answer
Correct answer: A
Explanation
Correct Answer:
Jack can be sure a message is from Jill by using her public key to decrypt the digital signature is correct.
In general, public keys encrypt and private keys decrypt. However, a digital signature—used to absolutely prove identity—works the other way: a hash is encrypted with the sender’s private key so that anyone decrypting it with the sender’s public key will have proof of identity.
Incorrect Answers:
Jack can be sure a message came from Jill by using his public key to decrypt it, Jack can be sure a message came from Jill by using his private key to decrypt it, and Jack can be sure a message is from Jill by using her private key to decrypt the digital signature are incorrect.
These are not proper descriptions of the use of public and private keys within a PKI system using digital certificates.
Discussion
Think the marked answer is wrong, or have a better explanation? Share it below — comments appear after review.
