Cryptography Reference
In-Depth Information
Basic Principles
1
This chapter serves as an introduction to the environment in which cryptog-
raphy finds common use today. We discuss the need for cryptography, as
well as the basic language and concepts that are used to describe a cryptographic
system.
At the end of this chapter you should be able to:
• Justify the need for information security.
• Identify some of the essential security requirements of the modern world.
• Appreciate the most significant risks to which information is exposed.
• Identify a number of different security services that cryptography can provide.
• Describe the basic model of a cryptosystem.
• Recognise the differences between symmetric and public-key (asymmetric)
cryptosystems.
• Appreciate the importance of identifying the assumptions about what an
attacker knows about a cryptosystem.
• Discuss what it means to break a cryptosystem.
It is very likely that anyone reading this topic already understands the need for
information security, and hence cryptography. However, we need to consider this
question, at least briefly, because it is extremely important that we understand the
role of cryptography in securing information. We will use the term
information
security
in a generic sense to describe the protection of information and
information systems. This involves the use of many different types of security
technologies, as well as management processes and controls.
Cryptography
provides the techniques that underpin most information security technologies.
This chapter will explore this concept in more detail. More precise explanations
of the core definitions relating to cryptography are provided in Section 1.4.1.
