One solution i can think of is,
You Create your own data and keep it stored on your device(can be anything, laptop,desktop,mobile etc). When you visit some host, it knows where to find your data(we assign a common known to all social port to our host), but needs your permission to download the data.So now when a relation of yours visits the same host we visited, It can tell our relation that what we have done on the host, only after we both use a common key.