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

System.Security.Cryptography.HMACSHA512

public class HMACSHA512 : HMAC
namespace System.Security.Cryptography { public class HMACSHA512 : HMAC { public bool ProduceLegacyHmacValues { get; set; } public HMACSHA512(); public HMACSHA512(byte[] key); } }