Multi-touch attribution is considered as holy grail in advertising industry. As advertisers are targeting users with multiple advertisements across different platforms and publishers, understanding how each of these touch points contributes to conversion is crucial—but this understanding has traditionally come at the cost of user privacy.

In last post we covered, Privacy Preserving Measurement (PPM) and discussed how Distributed Aggregation Protocol (DAP) works. Today, we'll explore how to implement a simplified version of the DAP using Python with Prio3 as our Verifiable Distributed Aggregation Function (VDAF). This implementation will support multiple clients, demonstrating how DAP can aggregate data from multiple sources while maintaining privacy.

In 1982, Andrew Yao proposed the Millionaire Problem which discusses how two millionaires can learn who is richest one without disclosing their actual wealth. They solve this problem by comparing their wealth using secure two party computation to ensure that they learn only the richest one and nothing else is revealed. The problem was later generalised for secure multiparty computation by Goldreich et al in 1987.