C# 9.0 in a Nutshell

Chapter 20. Cryptography

In this chapter, we discuss the major cryptography APIs in .NET:

• Windows Data Protection (DPAPI)

• Hashing

• Symmetric encryption

• Public key encryption and signing

The types covered in this chapter are defined in the following namespaces:

System.Security;
System.Security.Cryptography;

Overview

Table 20-1 summarizes the cryptography options in .NET. In the remaining sections, we explore each of these.

Table 20-1. Encryption and hashing options in .NET

Option	Keys to manage	Speed	Strength	Notes
File.Encrypt	0	Fast	Depends on user’s password	Protects files transparently with filesystem support. A key is derived implicitly from the logged-in user’s credentials. Windows only.
Windows Data Protection	0	Fast	Depends on user’s password	Encrypts and decrypts byte arrays using an implicitly derived key
Hashing	0	Fast	High	One-way (irreversible) transformation. Used for storing passwords, comparing files, and checking for data corruption
Symmetric Encryption	1	Fast	High	For general-purpose encryption/decryption. The same key encrypts and decrypts. Can be used to secure messages in transit
Public Key Encryption	2	Slow	High	Encryption and decryption use different keys. Used for exchanging a symmetric key in message transmission and for digitally signing files

.NET also provides more specialized support for creating and validating XML-based signatures in System.Security.Cryptography.Xml and types for working with digital certificates in System.Security.Cryptography.X509Certificates ...