Caution: This is just a personal idea derived based on two things; Blockchain, and recent privacy tech development under w3c,Turtledove

Browser has user's address (wallet address in terms of bitcoin)

Browser gives wallet address to SSPs, unique address is provided for each request (for cardinality check TTL can be added on address-es) i.e., whoever calls window.getUserAddress() will get the unique address

• this unique address may have a limited lifetime, considering blockchain transactions are little slower

SSPs/DSPs who want to read data related to the unique address can query on Blockchain

or One address per vendor can be created for the browser

Blockhain

• Full Nodes hosted by ad networks
• Full Nodes have data related to the unique address (another blockchain / store can contain the unique address to original address lookup, and only these nodes can do so, without even revealing the original address to node maintainer itself)
  • data: interest groups, categorical
  • prevents microtargeting by taking consenus when an address is being added in new interest group
    • consensus to check the size of Interest Group
  • user: can see what interest groups they are in as their addresses are added to IGs

Browser's selection of FullNode

• Browser's select Full Node using a nameservice or seed lookup kind of system (web3 solves)
• Full Node needn't be any specific SSP

Ad Rendering

• When Ad Renders or Click happens (x event) which SSP/DSP wants to keep track for budgeting and performance, browser will make a transaction in the blockchain to add the tuple information in blockchain store
• These information then can be queried by the client (can be ssp/dsp, basically client of the performance data)
• Blockchain gives out these data by taking consensus on the tuple's cardinality and the audience size on that cardinality
  • this can help in auto adjusting the tuples
  • this can help in retrieving faster information then relying on browser to push to some source