The other day, a senior in the family asked me if I could pop in the local convenience store, OXXO, to pay her tanda, run by a good friend of hers. I immediately inquired her how it was run now that, because of COVID-19, she was strictly staying at home. What she explained amazed me: an ad hoc mashup of money transfers, proof of payment as photos sent by WhatsApp, strung together by septuagenarians. I exclaimed: Eureka!

I made her payment and quickly put pen to paper. Santander's Digital Trust could well be the glue that sticks digitalized tandas together, as well as expanding its reach so that such a scheme purely built on peer to peer trust could be open to strangers.

What it does

e-Tanda has two main conceptual parts: the full, seamless digitalization of the tanda process as is, and the application of Santander's Digital Trust protocol to expand tandas so that organizers can publish tandas, including the definition of acceptance criteria for potential participants, and the ability to validate them with DT claims, and that prospective participants can use a discovery service: to find tandas that suit their needs and for which they can qualify.

How I built it

The prototype is in such an early stage that it's not usable at all.

I just put together the skeleton of a proxy that consumes DT services, the app backend (both in node.js, hosted in Heroku), as well as the very basic database that keeps the absolute minimum amount of data (a MySQL database, hosted, oddly enough, in Hostinger). The main design principle is "data is not the new oil, it's the new uranium" and it fits well with the filosophy of DT: don't store data if you can query it on the fly; don't query actual facts if you can validate claims in their stead.

I also started putting together a mobile client using Flutter for which I've just created a screen and started working on the API providers.

The definition, however, in terms of Epics, User Stories and the Minimum Viable Product is quite exhaustive. It can be found in the slide deck.

Challenges I ran into

The documentation is quite clear, thorough and the team has made sure the necessary tools to understand and be able to use the protocol are up and running. But it's time that was my main challenge. As my proposal is ambitious, once I found out that a submission could be made without a working prototype, I decided to focus on the definition rather than the execution, which I barely started. So the main challenge was time.

Accomplishments that I'm proud of

Going from Eureka moment to submission in less than a week... and keeping the video south of 5 minutes (one second less, to be exact).

What I learned

I learnt about security. I learnt about trust. I learnt in the Slack conversations that Santander has a top notch team at Santander Labs.

What's next for e-Tanda

Keep cracking on! It's an idea that deserves not to be forgotten in the tip of hackaton entries, but to see the light of day :-)

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