Page 333 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

looking through old, irrelevant information.

Data Protection Methods

One of the primary methods of protecting the confidentiality of data is

encryption. Chapter 6, “Cryptography and Symmetric Key
Algorithms,” and Chapter 7, “PKI and Cryptographic Applications,”
cover cryptographic algorithms in more depth. However, it’s worth
pointing out the differences between algorithms used for data at rest
and data in transit.

As an introduction, encryption converts cleartext data into scrambled

ciphertext. Anyone can read the data when it is in cleartext format.
However, when strong encryption algorithms are used, it is almost
impossible to read the scrambled ciphertext.

Protecting Data with Symmetric Encryption

Symmetric encryption uses the same key to encrypt and decrypt data.
In other words, if an algorithm encrypted data with a key of 123, it
would decrypt it with the same key of 123. Symmetric algorithms don’t
use the same key for different data. For example, if it encrypted one set

of data using a key of 123, it might encrypt the next set of data with a
key of 456. The important point here is that a file encrypted using a
key of 123 can only be decrypted using the same key of 123. In
practice, the key size is much larger. For example, AES uses key sizes
of 128 bits or 192 bits and AES 256 uses a key size of 256 bits.

The following list identifies some of the commonly used symmetric
encryption algorithms. Although many of these algorithms are used in

applications to encrypt data at rest, some of them are also used in
transport encryption algorithms discussed in the next section.
Additionally, this is by no means a complete list of encryption
algorithms, but Chapter 6 covers more of them.

Advanced Encryption Standard The Advanced Encryption
Standard (AES) is one of the most popular symmetric encryption
algorithms. NIST selected it as a standard replacement for the older

Data Encryption Standard (DES) in 2001. Since then, developers have