I am not sure I fully understand your question. However, it is not uncommon for a user ID (that has been de-personalized) to be used to identify users after a login (or other way to identify a specific user). If you provide such an ID in your implementation, you could do the kind of analysis suggested here.
Things to be aware of:
Hash Collisions - Logs of unique values with low traffic raises the risk of hash collisions. Data Warehouse does not have this issue so, it can be used as a work around.