Chapter 30. Using Cryptography with the .NET Framework: The Basics

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By Brian A. LaMacchia

IN THIS CHAPTER

• Setting the Stage: Key Definitions and Scenarios in Cryptography

• The Cryptographic Object Model of the .NET Framework

• Operating on Streams: CryptoStreams and ICryptoTransforms

• Using Symmetric Algorithms

• Using Cryptographic Hash Functions

• Using Keyed Hash Functions

• Random Number Generation and Key Derivation

• Using Asymmetric Algorithms

This chapter introduces the cryptography libraries and functions included in the .NET Framework in the System.Security.Cryptography namespace. On completion of this chapter, the reader should be able to

• Describe the contents of the System.Security.Cryptography namespace in the .NET Framework and the cryptographic object models.

• Demonstrate how to encrypt and decrypt data using symmetric (shared-key) and asymmetric (public key) algorithms.

• Demonstrate how to provide message integrity and authentication services through the use of digital signatures.

• Demonstrate how to compute cryptographic hashes and keyed hashes of data buffers and streams.

• Demonstrate how to combine cryptographic transforms using multiple wrapped instances of the CryptoStream class.

• Show how to generate cryptographically strong pseudo-random numbers and how to derive secret key material from passwords.

Chapter 31, "Using Cryptography with the .NET Framework: Advanced Topics," continues the discussion of cryptography in the .NET Framework and builds on the concepts introduced in this chapter.

Cryptography is the science of keeping messages secure. When discussing "message security," we typically are interested in one or more of the following three features:

• Confidentiality ” Keeping the contents of a message private so that only authorized parties can read it

• Integrity ” Ensuring that the contents of a message have not been tampered with while it is in transit from sender to recipient

• Authentication ” Ensuring that a message claiming to have been sent by a party actually originated with that party

As you program and develop applications with the .NET Framework, you may want these features for all or portions of your data. For example, you may want to use cryptography to secure your data from unauthorized access or detect if the data has been changed without authorization. The .NET Framework includes a comprehensive set of object classes that can be used to perform cryptographic operations.

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