The concept of rendering data passing between two points over an IP based network impervious to all
but the most sophisticated advanced persistent threats is BEST categorized as which of the following?

A.
Stream ciphers

B.
Transport encryption

C.
Key escrow

D.
Block ciphers

Explanation:
Transport encryption is the process of encrypting data ready to be transmitted over an insecure network.
A common example of this would be online banking or online purchases where sensitive information such
as account numbers or credit card numbers is transmitted.
Transport Layer Security (TLS) is a protocol that ensures privacy between communicating applications and
their users on the Internet. When a server and client communicate, TLS ensures that no third party may
eavesdrop or tamper with any message. TLS is the successor to the Secure Sockets Layer (SSL).
Incorrect Answers:
A: A stream cipher is used for encrypting data when the size of the data is unknown (such as streaming a
movie). The data is encrypted one bit at a time as it is streamed. RC4 is a commonly used stream cipher. A
stream cipher is a specific description of something that is used to encrypt a stream of data. It is not a
concept of securing data between two points.C: Key escrow is an arrangement in which the keys needed to decrypt encrypted data are held in escrow
so that, under certain circumstances, an authorized third party may gain access to those keys. It is not a
concept of securing data between two points.
D: A block cipher is used to encrypt a chunk of data (block) before transmitting the data. A block cipher is
a specific description of something that is used to encrypt a block of data. It is not a concept of securing
data between two points.

http://en.wikipedia.org/wiki/Transport_Layer_Security
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis,
2014, pp. 249, 250, 262