code: function requestPQ(callback, channel) {
      // Create a nonce for the client
      var clientNonce = utility.createNonce(16);
      mtproto.service.req_pq({
          props: {
              nonce: clientNonce
          },
          channel: channel,
          callback: function (ex, resPQ) {
              if (clientNonce === resPQ.nonce) {
                  var context = {
                      resPQ: resPQ,
                      channel: channel
                  };
                  callback(null, context);
              } else {
                  callback(createError('Nonce mismatch.', 'ENONCE'));
              }
          }
      });
  }
docs: Request a PQ pair number