Which of the following must a user implement if they want to send a secret message to a coworker by embedding it within an image?

A.
Transport encryption

B.
Steganography

C.
Hashing

D.
Digital signature

Explanation:
Steganography is the process of concealing a file, message, image, or video within another file, message, image, or video.
Note: The advantage of steganography over cryptography alone is that the intended secret message does not attract attention to itself as an object of scrutiny.
Plainly visible encrypted messages, no matter how unbreakable will arouse interest, and may in themselves be incriminating in countries where encryption is illegal.
Thus, whereas cryptography is the practice of protecting the contents of a message alone, steganography is concerned with concealing the fact that a secret
message is being sent, as well as concealing the contents of the message.
Incorrect Answers:
A: Transport encryption encrypt the payload data
C: A hash function is used to map digital data of variable size to digital data of fixed length.
D: A digital signature is similar in function to a standard signature on a document. It validates the integrity of the message and the sender.

Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, Sixth Edition, Sybex, Indianapolis, 2014, p 249, 155, 261, 323
http://en.wikipedia.org/wiki/Steganography