<PackageReference Include="NETStandard.Library" Version="2.0.0-preview2-25401-01" />

System.Security.Cryptography.PaddingMode

public enum PaddingMode
namespace System.Security.Cryptography { public enum PaddingMode { ANSIX923 = 4, ISO10126 = 5, None = 1, PKCS7 = 2, Zeros = 3 } }