blockchain apps with real use for real people.

We believe that blockchain apps don’t have to be complicated.
And they shouldn’t be.

what makes us tick started with a simple observation: Blockchain is a fascinating new technology – but where are the real-world use cases with a broad adoption? Not even Bitcoin, the cryptocurrency for which the first iteration of a Blockchain was created, really counts – the number of participants outside of the tech world is slim.

Here’s how we see it:

  • Blockchain is currently hyped, but there are real benefits to be had
  • Use cases where blockchain really gives you an advantage over existing technology are few and far in between
  • For blockchain applications to succeed, end users must understand their value without being lectured on the underlying technology
  • To reach mass adoption, blockchain must be part of the back-end, with a secure but easy to use translation into the user experience

apps so user friendly,
you forget about the blockchain.

our projects


airproof gives security to guests of private apartment rentals – think airbnb.

The problem:

  • Oftentimes, guests depart without the host present – “just leave the key on the table and pull the door shut”. There is no handover.
  • Hosts of private rentals oftentimes are not professionals – and sometimes, they are also not completely honest.
  • How do you prove that you left the apartment with everything intact and nothing missing?


The solution:

  • With airproof, you document your departure in a short video. Go from room to room. Last, film yourself putting the key on the table and pulling the door shut.
  • airproof takes a fingerprint of the video – together with the time and GPS location from your phone.
  • The fingerprint is written into the Bitcoin Blockchain: This gives you a solid “proof of existence” for this video that is tamper-proof and timestamped to the time of your departure.

airproof uses a widely proven blockchain use case.

Timestamping on the blockchain

In v1 of the app, we work with opentimestamps, who are aggregating timestamp requests from various apps and write them into the bitcoin blockchain. This enables us to offer the service free of charge.

In v2, we are looking into alternatively also writing the timestamps into the blockchain ourselves to improve the speed and accuracy of the timestaming. Every airproof video’s fingerprint will then be written into the blockchain using a special transaction type, the so called op_return. This transaction type does not require a recipient (we are not moving money or assets), but allows us to write a certain number of bytes into the blockchain. This space is used for the fingerprint (to be exact, the SHA 256 hash value) of the video.


Where is the innovation? There are many timestamping services available!

There are, absolutely! Just… look at them! There are the purely web based services – useless if you are on the go. And then there are the generic ones, designed more as a “proof of concept” than for a specific application. And don’t get us started on the BADLY designed ones…

airproof is the first app which puts the concrete use case first, a great user experience second, and blockchain third. Our target group does not know what an op_return statement is, nor should they have to care.


about us is founded and powered by Alexander, Christoph and Florian.

We all work for management consulting firms by day and join forces for
In the words of Gary Vaynerchuck, this is our hustle. In our words, we just can’t not do this.
Every one of us has run his own business in IT before, but we are not developers first. This is our core advantage, believe it or not. We think in problems, we think in users, we think in markets, we think in usability. Then – and only then – do we think about the tech behind it.


Alexander Kahlmann

Alexander Kahlmann

Founder & CEO

Dr. Christoph Mayer

Dr. Christoph Mayer

Founder & CTO

Florian Hollender

Florian Hollender

Founder & COO

read more on our blog blog

We are blogging our thoughts on blockchain technology, on how it is to run an blockchain company “on the side” and let you take part in the process of developing our apps. Currently, we are developing the first version of airproof. Join the ride!