System.Security.Cryptography is not annotated

[NN---]

Create methods never return null. E.g. https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.des.create?view=netframework-4.7.2#System_Security_Cryptography_DES_Create

https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography?view=netframework-4.7.2 Samples

var des = DES.Create();
var desEncryptor = des.CreateEncryptor(); // Possible NRE

var aes = Aes.Create();
var aesEncryptor = aes.CreateEncryptor(); // Possible NRE