Explanation/Reference:
Explanation:
For large quantities of sensitive information, symmetric key encryption (using a secret key) is more efficient.
Public key cryptography uses two keys (public and private) generated by an asymmetric algorithm for protecting encryption keys and key distribution, and a secret key is generated by a symmetric algorithm and used for bulk encryption. Then there is a hybrid use of the two different algorithms: asymmetric and symmetric. Each algorithm has its pros and cons, so using them together can be the best of both worlds.
In the hybrid approach, the two technologies are used in a complementary manner, with each performing a different function. A symmetric algorithm creates keys used for encrypting bulk data, and an asymmetric algorithm creates keys used for automated key distribution.
When a symmetric key is used for bulk data encryption, this key is used to encrypt the message you want to send. When your friend gets the message you encrypted, you want him to be able to decrypt it, so you need to send him the necessary symmetric key to use to decrypt the message. You do not want this key to travel unprotected, because if the message were intercepted and the key were not protected, an evildoer could intercept the message that contains the necessary key to decrypt your message and read your information. If the symmetric key needed to decrypt your message is not protected, there is no use in encrypting the message in the first place. So we use an asymmetric algorithm to encrypt the symmetric key. Why do we use the symmetric key on the message and the asymmetric key on the symmetric key?
The reason is that the asymmetric algorithm takes longer because the math is more complex. Because your message is most likely going to be longer than the length of the key, we use the faster algorithm (symmetric) on the message and the slower algorithm (asymmetric) on the key.
Incorrect Answers:
B: For large quantities of sensitive information, symmetric key encryption (using a secret key) is more efficient. Using public and private keys for encryption and decryption is asymmetric key encryption.
C: Software encryption is not an answer on its own. We need to determine what type of software encryption to use.
D: Elliptical curve cryptography (ECC) is a public key encryption technique. Symmetric key encryption is more efficient for large amounts of data.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 793