The BCL provides classes for manipulating all elements of the .NET runtime’s Code Access Security model, including security policies, security principals, permission sets, and evidence. These classes also support cryptographic algorithms such as DES, 3DES, RC2, RSA, DSig, MD5, SHA1, and Base64 encoding for stream transformations.

For more information, see the following namespaces:

System.Security
System.Security.Cryptography
System.Security.Cryptography.X509Certificates
System.Security.Cryptography.Xml
System.Security.Permissions
System.Security.Policy
System.Security.Principal