You’ve decided to authenticate the source who initiated a particular transfer while ensuring integrity of the data
being transferred. You can do this by:
A.
having the sender encrypt the message with his private key.
B.
having the sender encrypt the hash with his private key.
C.
having the sender encrypt the message with his symmetric key.
D.
having the sender encrypt the hash with his public key.
Explanation:
A hash will ensure the integrity of the data being transferred. A private key will authenticate the source (sender).
Only the sender has a copy of the private key. If the recipient is able to decrypt the hash with the public key,
then the recipient will know that the hash was encrypted with the private key of the sender.
A cryptographic hash function is a hash function which is considered practically impossible to invert, that is, to
recreate the input data from its hash value alone. The input data is often called the message, and the hash
value is often called the message digest or simply the digest.
The ideal cryptographic hash function has four main properties:
it is easy to compute the hash value for any given message
it is infeasible to generate a message from its hash
it is infeasible to modify a message without changing the hash
it is infeasible to find two different messages with the same hash.
Incorrect Answers:
A: Having the sender encrypt the message with his private key would authenticate the sender. However, iswould not ensure the integrity of the message. A hash is required to ensure the integrity of the message.
C: Having the sender encrypt the message with his symmetric key will not authenticate the sender or ensure
the integrity of the message. A hash is required to ensure the integrity of the message and the hash should be
encrypted with the sender’s private key.
D: Having the sender encrypt the hash with his public key will not authenticate the sender. Anyone could have a
copy of the sender’s public key. The hash should be encrypted with the sender’s private key as the sender is
the only person in possession of the private key.https://en.wikipedia.org/wiki/Cryptographic_hash_function