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Basis of Cryptography • Chapter 9 527

refers to the processing power and time required to encrypt and decrypt a message,
and ease of implementation refers to an algorithm’s predisposition (if any) to hardware
or software usage. Each algorithm has different strengths and drawbacks, and none
of them are ideal in every way.There are many questions about the number of dif-
ferent cryptographic algorithms on the Security+ exam.This section discusses the
key algorithms, which fall into three main categories:

■ Symmetric cryptography

■ Asymmetric cryptography
■ Hashing algorithms

TEST DAY TIP
All of the algorithms presented in this chapter are open algorithms,
which means that the internals of the algorithms, while they may or
may not be covered by patents, are open for examination by the public.
In contrast, proprietary algorithms keep the internal workings secret
and are slightly harder to crack at their initial release. Open standards
algorithms are usually the most secure. Proprietary algorithms are also
based on security through obscurity, but that obscurity has prevented
public examination that could discover undiscovered flaws.

What Is Encryption?

Encryption is a form of cryptography that “scrambles” plaintext into unintelligible
ciphertext. Encryption is the foundation of such security measures as digital signa-
tures, digital certificates, and the Public Key Infrastructure (PKI) that uses these
technologies to make computer transactions more secure. Computer-based encryp-
tion techniques use keys to encrypt and decrypt data.A key is a variable (sometimes
represented as a password) that is a large binary number—the larger, the better. Key
length is measured in bits, and the more bits in a key, the more difficult the key will
be to “crack.” For example, a 40-bit key is considered insecure by today’s standards,
but it can have a value between 1 and 2^140 (1,099,511,627,776, over a trillion).
The key is only one component in the encryption process. It must be used in
conjunction with an encryption algorithm (a process or calculation) to produce the
ciphertext. Encryption methods are usually categorized as either symmetric or

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