Auto authentification

Hi All, I need a litle help. I would like to solve that, you don't have to sign in every time, it goes automatically log in to user. So i would like to create a Mashup access without login. I tried with Mashup parameter: USER, and PASSWORD, but no success. It will also be asked to sign in. I tried with Application Key, x-thingworx-session=true, but the result is: you mustn't log in, but it goes with error. Am I missing something? Can someone help me? Thank you, Ilona