Many blockchain projects can feel like a solution looking for a problem (cats-stuck-up-trees on the blockchain, anyone?), we’ve rooted Tap around the fundamental principles of the technology and guess what? It just works.

In this article we look at how we’ve used the Stellar blockchain to improve transparency and trust when it comes to data requests, i.e. the movement of personal data between organisations and individuals. If you want to learn more about Tap read about how we’re shaping the privacy universe.

Why blockchain?

To put it simply, a blockchain is digital ledger that records transactions, or anything else for that matter, permanently. You can’t change or remove anything you record in it.

It’s helpful to understand a blockchain as a book (a bit like the one below) where records of transactions are recorded, where everyone can see them and the transactions can’t be erased or tampered with.

Of course, there’s more to it than that, and Blockchain technology is pretty deep. It’s beyond the scope of this blog post to cover it all, but here is a primer if you do want to learn more.

So why does blockchain work for Tap?   We’ve written about Tap’s mission of building trust and transparency between individuals and organisations. Trust and transparency are well aligned to the function of a ledger of entries that cannot be erased or changed and that allows people to look and see the transactions that took place.

Data is a pretty complex, far reaching and amorphous thing. We can’t really see it, touch or feel it. We just know it’s there.

But what if we could record or audit when data moves between an organisation and say one of its customers? What if we have an audit log that places no data on the blockchain but just shows the data has moved from one place to another? A system like this could hold the key to a more transparent and trustworthy data economy.

How we use the Stellar blockchain to build trust and transparency

Stellar is an open-source, decentralised protocol. It provides a public ledger that allows transactions between two or more parties.

Stellar offers a scalable and low cost blockchain solution which is vitally important in such a large data economy.

How does Stellar work for Tap?  When a user opens the Tap app on their phone users are able send a data request, such as subject access request, to an organisation they believe holds their personal data.

When a user sends a data request to an organisation, a record of this transaction (but not any personal data!) is recorded on the Stellar public ledger (or digital book as we referred to it as). It also works the other way round; when an organisation sends a data response back to the customer’s personal data-locker, a record of this transaction (and again, no personal data!) is logged on the Stellar public ledger.

As we’ve followed the practice of ‘Privacy by Design’, it was important that no data was put onto a blockchain for risk of security and personal privacy for both the individuals and organisations. As such, no personal data is put on the blockchain in any way, shape or form.

We’ve drafted up a simple diagram that shows how this works…


Now, go see for yourself!

What is really cool is that you can go and see the audit trail or transactions of data requests sent between individuals and organisations by examining the Stellar blockchain.

You can do this on any Stellar blockchain explorer. In this instance I’ve linked to one called Stellar Scan. There are a few of these explorers around on the web for you to look at transactions. These explorers provide a view of the public ledger for anyone to visit and see all transactions that takes place on the Stellar blockchain.

For example; I sent a request to an organisation (Costa Coffee) via the app. Once I received a response back from Costa Coffee I could see this audit log via the Stellar blockchain explorer. For now it shows a long technical-looking number that simply shows that the transaction has taken place. Ok this screenshot is no Mona Lisa, but the key point of showing that I have sent a data request and the organisation has responded is pretty significant.


Unique Transaction ID on Stellar Blockchain

We hope using a public ledger means that NGOs and data regulators can use this to map out for reports on the data landscape, or start to build a privacy Trustpilot to showcase organisations that take privacy seriously, and those that don’t. As the blockchain space matures, we hope that user experiences will improve in parallel and we will see a future where open source tools can further help this visualisation.

It just fits

Blockchain works towards our mission to build trust and transparency between organisations and individuals. Using the Stellar public ledger means we can build audit trails around the exchange and movement of personal data between organisations and individuals.

The impact of this could lead to better data insights, safer more transparent movement of data, and the prospect of improved trust between customers and organisations.

Please do share, and comment if you have further technical questions. If you want to learn about Tap visit us at

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