Book Image

Improving your C# Skills

By : Ovais Mehboob Ahmed Khan, John Callaway, Clayton Hunt, Rod Stephens
Book Image

Improving your C# Skills

By: Ovais Mehboob Ahmed Khan, John Callaway, Clayton Hunt, Rod Stephens

Overview of this book

This Learning Path shows you how to create high performing applications and solve programming challenges using a wide range of C# features. You’ll begin by learning how to identify the bottlenecks in writing programs, highlight common performance pitfalls, and apply strategies to detect and resolve these issues early. You'll also study the importance of micro-services architecture for building fast applications and implementing resiliency and security in .NET Core. Then, you'll study the importance of defining and testing boundaries, abstracting away third-party code, and working with different types of test double, such as spies, mocks, and fakes. In addition to describing programming trade-offs, this Learning Path will also help you build a useful toolkit of techniques, including value caching, statistical analysis, and geometric algorithms. This Learning Path includes content from the following Packt products: • C# 7 and .NET Core 2.0 High Performance by Ovais Mehboob Ahmed Khan • Practical Test-Driven Development using C# 7 by John Callaway, Clayton Hunt • The Modern C# Challenge by Rod Stephens
Table of Contents (26 chapters)
Title Page
Copyright and Credits
About Packt
What to Know Before Getting Started
Files and Directories
Advanced C# and .NET Features

Chapter 19. Cryptography

This chapter describes problems in cryptography. The first few problems ask you to use cryptographic systems that were once state-of-the-art but that are now insecure. They are purely for fun and are of historical significance. Later problems use modern, secure techniques, such as the .NET Framework's cryptographic library, to build secure programs.

When studying cryptography, it's useful to know a few basic terms. A key is a piece of secret information that you can use to encrypt and decrypt messages. Sometimes, a password is a key. Other times, a password is used to generate a key in a format suitable for use by a particular encryption algorithm. A message that is not encrypted is called plaintext. The encrypted version of plaintext is called ciphertext.

Traditionally, plaintext and ciphertext are written in five-letter groups of uppercase letters without punctuation or spaces, at least for older encryption systems such as the Caesar substitution and Vigenère ciphers...