def reg_registration_data(client_data_json)
      ::U2F.urlsafe_encode64(
        [
          5,
          origin_public_key_raw,
          key_handle_raw.bytesize,
          key_handle_raw,
          cert_raw,
          reg_signature(client_data_json)
        ].pack("CA65CA#{key_handle_raw.bytesize}A#{cert_raw.bytesize}A*")
      )
    end
def reg_registration_data(client_data_json)
      ::U2F.urlsafe_encode64(
        [
          5,
          origin_public_key_raw,
          key_handle_raw.bytesize,
          key_handle_raw,
          cert_raw,
          reg_signature(client_data_json)
        ].pack("CA65CA#{key_handle_raw.bytesize}A#{cert_raw.bytesize}A*")
      )
    end
The registrationData field returns in a RegisterResponse Hash.

 client_data_json - The JSON encoded clientData String.

 Returns a url-safe base64 encoded binary String.