There are many ways to secure different parts of your application. The security of running code in .NET revolves around the concept of Code Access Security (CAS). CAS determines the trustworthiness of an assembly based upon its origin and the characteristics of the assembly itself, such as its hash value. For example, code installed locally on the machine is more trusted than code downloaded from the Internet. The runtime will also validate an assembly's metadata and type safety before that code is allowed to run.
There are many ways to write secure code and protect data using the .NET Framework. In this chapter, we explore such things as controlling access to types, encryption and decryption, random numbers, securely storing data, and using programmatic and declarative security.