Protect modules fake

Would one idea validate the following?

• Send data from the GPS module to the Espruino along with a token. (This token must depend on the latitude and longitude given by that module.)
  
  

Espruino sends this data to the cloud and from there:

If that latitude and longitude change, then it is an invalid token.
If the internal algorithms match, then they are correct data.

This for the moment seems a good idea.

But for that I have to trust that the encoding algorithm generates the token based on its length and latitude can not be observed, and that leads me to my other post http://forum.espruino.com/conversations/310068/ # comment13841208