<PackageReference Include="NETStandard.Library" Version="2.0.1" />

System.Security.Cryptography.HMACSHA1

public class HMACSHA1 : HMAC
namespace System.Security.Cryptography { public class HMACSHA1 : HMAC { public HMACSHA1(); public HMACSHA1(byte[] key); public HMACSHA1(byte[] key, bool useManagedSha1); } }