Which of the following functions provides an output which cannot be reversed and converts data into a
string of characters?

A.
Hashing

B.
Stream ciphers

C.
Steganography

D.
Block ciphers

Explanation:
Hashing refers to the hash algorithms used in cryptography. It is used to store data, such as hash tables
one of its characteristics is that it must be one-way – it is not reversible.
Incorrect Answers:
B: A stream cipher is similar to a block cipher in that they are both symmetric methods of cryptography.
The difference is that with a stream cipher the data is encrypted one bit, or byte, at a time whereas with a
block cipher the algorithm works on chunks of data.C: Steganography is the process of hiding a message in a medium such as a digital image, audio fi le, or
other file. In theory, doing this prevents analysts from detecting the real message. You could encode your
message in another fi le or message and use that fi le to hide your message.
D: A block cipher is a symmetric method in cryptography that encrypts data in chunks; very similar to
stream ciphers.

Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis,
2014, pp. 248, 255, 291
http://en.wikipedia.org/wiki/Hash_function
http://www.webopedia.com/TERM/H/hashing.html