Which of the following is a method for transforming a message into a masked form, together with a
way of undoing the transformation to recover the message?

A.
Cipher

B.
CrypTool

C.
Steganography

D.
MIME

Explanation:
A cipher is a cryptographic algorithm that performs encryption or decryption. It is a
series of well-defined steps that can be followed as a
procedure. The cipher transforms a message into a masked form, together with a way of undoing
the transformation to recover the message.
When using a cipher the original information is known as plaintext, and the encrypted form as
ciphertext. The ciphertext message contains all
the information of the plaintext message, but it is not in a readable format.
The operation of a cipher usually depends on a piece of auxiliary information, called a key or a
cryptovariable. The encrypting procedure is
varied depending on the key, which changes the detailed operation of the algorithm. A key must be
selected before using a cipher to encrypt
a message. Without knowledge of the key, it is impossible to decrypt the ciphertext into plaintext.
Answer option B is incorrect. CrypTool is free software and an e-learning tool illustrating
cryptographic concepts.
Answer option C is incorrect. Steganography is the art and science of writing hidden messages in
such a way that no one, apart from the
sender and intended recipient, suspects the existence of the message, a form of security through
obscurity.
Answer option D is incorrect. MIME stands for Multipurpose Internet Mail Extensions. It is a
standard for multi-part, multimedia electronic mail
messages and World Wide Web hypertext documents on the Internet. MIME provides a mechanism
for exchanging non-text information, such
as binary data, audio data, video data, and foreign language text that cannot be represented in ASCII
text.