Assume that Alice and Bob want to exchange messages over the Internet. They agree on an encryption cipher and a scheme for exchanging encryption keys in a secure manner. Which of the following best describes their requirement for using a cryptographic hash for authentication?

a. If they use an encryption scheme that uses keys longer than 2256, they wont need to use a cryptographic hash for authentication. Otherwise they will have to use a cryptographic hash, MAC, or HMAC to ensure the messages they exchange are authentic and havent been changed by an attacker.

b. If they use AES for encryption, they wont need to use a cryptographic hash for authentication. If they choose any other cipher, they will have to use a cryptographic hash MAC, or HMAC to ensure the messages they exchange are authentic and havent been changed by an attacker.

c. It doesnt matter what encryption method they use. For authentication, they must always use a cryptographic hash MAC, or HMAC.

d. It doesnt matter what encryption method they use. For authentication, they must always use an HMAC.

e. None of the above