Christian Decker: The First Ph.D.
By: Ivana Mitrović
Tags: Blockchain, Blockchain Technology, Startup Life, Startup, Technology

Today, we sit down with Christian Decker, the Bitcoin core developer working in Blockstream, and the first doctor of philosophy in Bitcoin.

Christian became a Bitcoin enthusiast from the very beginning. In 2009, he got involved in a small community at that time, and he started to contribute in 2012.

He was offered a Ph.D. candidate position in the distributed computing group at ETH Zurich. The result was the world’s first Ph.D. dissertation about Bitcoin. Christian now works as a Bitcoin core developer in Blockstream, the leading provider of blockchain technologies.

In this episode, we talk with Christian about the early days of the Bitcoin community in Switzerland, why he chose Bitcoin for his Ph.D., and how it is to work in a team distributed across three continents

The video podcast is available on CV Labs Youtube channel, or as an audio version on Spotify.

How did you first get into Bitcoin?

I first learned about Bitcoin from the white paper…sometime in 2009. So, in the first year that the paper was out, I was doing my master’s in distributed computing, which matched nicely with the Bitcoin topic.

So, I started looking into it and participated in the early discussions on Bitcoin Talk, which back then was still on Bitcoin.org. We just started discussing technical topics. The debate wasn’t really about Bitcoin being a currency. It was more like…hey, this is something cool that we should have and that we should work on.

We started being friends, and in 2011 we had our first meetup here in Zurich — with four people. Two of them are now in America and leading successful companies.

And yeah, at some point, my hobby turned into a full-time job when I started doing my Ph.D. on it. And three years later, I was the first Bitcoin Ph.D. and got started working on the Lightning network.

We heard about vending machines where you could purchase chocolate bars with Bitcoin.

That is true. The company Selecta was gracious enough to offer us a free vending machine. We reached out only to have contact with somebody from whom we could buy it cheaply…Selecta built an entirely new machine and shipped it to us.

We had two working students, and to encourage them, we had the bottom of the vending machine filled up with beer. And as soon as they could get a payment through Bitcoin working, they could grab a beer. I’ve never seen students more engaged in their projects. In the end, those two students did very well. And we’re still friends today.

That was one of the student projects we did. A couple of more followed.

Did you operate other payment infrastructure at the time already?

We always built a couple of prototypes, but we never went beyond the prototype stage.

We had prototypes for access points where you could log in and pay for all the volume you used without having a priori relationship with the access point provider.

We had a Bluetooth based hardware wallet built by one of the students. He came back for his master thesis, and he made this Blue Wallet. We had many more exciting projects.

What about mining. How was mining done at ETH at the time when you were there?

I didn’t mine at ETH. I mined way before.

I was living in a student dorm, and I was administering the service there. And at some point, I decided that this Bitcoin stuff is cool. I thought maybe I could just have it run on a computer in my room.

So, I started it, and a couple of months later, I noticed that it was now suddenly worth something. It was like 5 cents or so for a Bitcoin.

So, then I rediscovered Bitcoin. And it turned out that I had…like… 100 Bitcoins sitting there. I immediately sold them…worst decision ever.

ETH is a very research-driven institution. But there’s occasional interaction with the industry. What was the interest of the industry at that time?

One interaction worth mentioning was with the company Selecta. They have an excellent internal research group. So, when we reached out, they were approachable and were opened to discuss potential collaborations.

When we started talking, they helped us out…especially by lending us one of their quite expensive machines. So that’s a lot of trust they had in us.

We had a couple of master’s thesis students working with external companies. I’m not sure that we had any involving Bitcoin…But we had a credit card processor and a network service provider working with us on separate projects.

All of them were excellent interactions. I think the name ETH alone opened a lot of doors.

You are a part of a small team that is implementing the Lightning network. Explain what the Lightning Network does and what is it supposed to be when it’s finished?

So Lightning is attempting to break through the blockchain limitations by leveraging blockchains as the base layer, on which we build additional functionality.

In Bitcoin, one of the limitations that we have is blockchain scalability.

The blockchain can be seen as a global medium shared by all of the network participants.

So, we need to build a layer on top of Bitcoin that allows us to have more efficient use of that base layer while providing additional use cases.

Lightning’s specific goals are that we want to remove the latency from sending a transaction to it being confirmed. This, on the Bitcoin base layer, can take minutes, if not hours, depending on how lucky you are and how much fees you added to your transactions.

With Lightning, the immediate real-time settlement of transactions increases the scalability of the network as such.

It does it by taking some funds and allocating them to a contract between two people and moving back and forth those funds unlimited time before net settling those interactions to the blockchain.

In that case, a Bitcoin transaction can represent any number of off-chain interactions. So, by not having a permanent trace of every single payment reflected as a transaction on the blockchain, Lightning will increase the network’s privacy.

How did you initially start with the Lightning Network?

The idea of these off-chain protocols is pretty old.

The initial “simple micropayment channels,” as we call them, date back to 2013. Back then, they were simple in the sense that we could only send incremental amounts in one direction and never send funds back.

During my Ph.D. studies, which topic was scalability and security of Bitcoin, one of the potential solutions for the scalability was using these payment channels. To make them bi-directional. And to create a network of these channels that can reach any point in this network. So, the last publication for my Ph.D. was one construction for these bi-directional channels called “duplex micropayment channels.”

I started implementing it, but at the same time, Joseph Poon and Thaddeus Dryja published the Lightning Network paper, and they stole all the thunder.

So, after I finished my Ph.D., the question was, do I now pursue my network and try to get that off the ground? Or do I join the existing team around Lightning?

Since the network’s strength comes from everybody able to interact with everybody else, creating two segregated networks doesn’t help at all.

That’s why I decided that I would put my work on the side and join the Lightning team to build a more significant and more useful network. Always keeping in mind what I had researched and what I had learned. And trying to get all of the right trade-offs back into the Lightning Network.

And that, in the end, turned out to be a proposal which we published two years ago…and we’re working towards that. So, once I had the decision that I wanted to join the Lightning team, it was pretty easy…

It wasn’t a hard choice to decide to join Blockstream, one of the biggest names when it comes to Bitcoin and to start working there.

We know that you are a top-level computer scientist, but we also want to know you as a person. What attracted you to computer science in the first place? And how did Bitcoin white paper first reach you?

Something that helps when getting started with computer sciences is a love for tinkering and a creative process to explore technology. I remember that as a kid, I was always the guy who took apart his cassette player…so my parents had to buy quite a few of them.

So, I think having this kind of technical interest will steer you towards…at least an engineering discipline. And computer science is one of the engineering disciplines that are easiest to pick up because you don’t need an oscilloscope, and you don’t need to have a soldering machine.

You just need a computer. So it’s something that you can get lost in quite easily.

I first read about the Bitcoin white paper on a blog. I can’t remember which one it was. But it was back then when Google searches for Bitcoin was returning three or four results. One of them was Satoshi’s posts on the crypto mailing list. So, it wasn’t too hard to find that paper and to dig into it. And it was something that I had been thinking about as well.

And suddenly, this solution claims to be able to do something that everybody considered to be impossible. And it was an elegant solution.

Not that I got it right from the get-go…I had to read this paper five or six times to start to begin understanding it. But it turns out it was an excellent construction, and it just meshed with my interests.

Why were you interested in a solution like Bitcoin? What does Bitcoin represent for you?

Bitcoin represents, for me, an experiment that goes beyond what we thought was possible. Having a group of people agree on a state and changes to that state without trusting each other. A transaction is something that I can authorize, but everybody else has to accept.

So, this global consensus system in which we don’t know who the participants are…we don’t even know how many there are…and we are still able to make progress and agree about what the current state is and what the valid and invalid transitions are. From a purely technical point of view, it’s doing something that we were thinking was impossible.

Nowadays, there are monetary, currency, and political aspects of Bitcoin. But back in the past, it was just about this incredible achievement that we could do something that we thought was impossible.

Is that why you decided to do a Ph.D. in Bitcoin? We know that you had the first Ph.D. in Bitcoin.

Initially, when I pitched Bitcoin as a topic to my professor, Bitcoin was my hobby. Back then, people thought that I’m crazy to think of it.

When I first told my parents that I’m just looking into Bitcoin, I haven’t still invested anything…I had to assure them immediately that I wasn’t crazy, that I haven’t fallen for it, and that Bitcoin is not a scam.

I was initially reluctant to make Bitcoin the topic of my Ph.D. because…well…who could know if it’s still going to be around in three years when I needed to wrap up my research. So I tried to get some exposure to Bitcoin in a couple of different ways but not too much.

So, I wrote down what I liked about Bitcoin and what I didn’t like about Bitcoin. I also wrote down what I want to achieve when working with Bitcoin. I ended up with a 16-page document that I showed to my professor. And he said he’ll give me a year of probation. And then we can reconsider the topic in a year.

Recently I found that paper again. It was all yellow from the sun. It was fascinating. It brought me back quite a few years in the past.

Tell us more about your work with students.

I had a lot of fun…, especially with the student projects. We came up with thesis ideas for semester thesis, bachelor thesis, and master’s thesis. That was a productive way of exploring the space by coming up with ideas for a project that we’d like to do and then looking for students that might fit that project and then following them along.

It taught me a lot about being flexible when setting goals for this kind of project. You always want to have one or two backup positions where you can say that this is highly exploratory. And that you don’t know if it will take three months or six months to complete.

We always had a backstop where we would say that we’ve seen it’s not working out because it’s too complicated. Maybe there was a roadblock we didn’t foresee. But at least we always had backstops to which we could fall back on and salvage the project. I’m pretty happy to say that all my students got good grades.

And besides the student projects, we also had lectures…but those were way more structured…but still creative. We got to introduce Bitcoin to a lot of students.

How does your research experience at university compares to working in a startup?

It’s different. During my Ph.D., it was always a chase for something new. You were always looking for the next big thing and trying to work on it.

So, you postulate your theories, and then you prove them. And in a couple of months, you’re done with that project. And then you move on with life

You never get to implement stuff or get users to use your software. That was something that I was lacking.

And now that we have products, we have this open-source project called Lightning; we do have users… and boy oh boy…supporting users is hard.

But it’s also really good to see your product, that a couple of months ago was only something on paper, in the hands of users and to see where the actual usability problems are.

And right now, I am in a nice position where I can balance research and work on a product quite nicely.

How is it to work in an extremely decentralized team?

It’s hard to get started with sitting home alone the whole day. It is something you have to get used to…especially if you previously had an office, so when you leave in the evening, that’s it.

Initially, I had some real issues ending my workday, because my computer was just there…

For example, I was watching a movie, but I could just do one last thing instead. So it’s a discipline that you have to learn.

Now beyond the individual developer… there’s the team aspect. We’re in an extreme situation where we have Rusty sitting in Australia, me sitting in Europe, and Lisa sitting in Texas. So we’re spanning the globe when it comes to time zones. And that makes meetings hard. But there is a way to do it.

And one of the positive note, there are several positives aspects to this situation as well. Mainly that there’s always somebody to answer your questions.

So if we have a user who wants to have a quick chat with somebody…to get help, somebody is always online and probably reachable.

Working in a team like ours also means that…you have to organize your work so that you can have a time where you’re the only one online. So, you can concentrate on your work and work on your backlog. And then you have handover periods where you talk to each other because two of you are online at the same time.

So, at the end of the day, we hand over our work, and we catch up on where we are standing. With this, you get much concentrated interactions with the individual team participants.

Also, there is the overarching structure, which is the protocol specification effort…which spans several teams. They happened to overlap quite nicely with my time zone…so I can discuss quite a lot with them.

What’s your strategy to separate your work time and your free time?

Something that I started doing quite early was to simulate a commute. So around 6:00 PM, I have an alarm that goes off. So, then I walk to the main train station, which is about 45 minutes by foot. And I also walk back.

So, having this ritual of going somewhere every day and then going back…even if it’s just to buy bread for dinner…it gets you into a certain rhythm.

So, in this case, I think the critical point is having a rhythm. You should structure your day so that you simulate as much as possible the office life… even if it’s just you. That includes the whole grooming routine… from the morning to the evening routine.

And during the times that I’m working, I always silence my phone. And I always silence all kinds of other distractions…unless I have one of my time slots where I planned to pick this stuff up and respond…and interact.

How often do you meet face to face with your team members?

Well…this year is a bit special, as all conferences were postponed or canceled. I would be traveling quite a lot during the early to mid-year because there are many conferences during those times. So in that way, I get to interact quite a lot with people despite working from home.

And that’s something that I enjoy a lot. Going out and interacting with people. Asking users what they are working on and how we can help. So, that’s been a bit more complicated during this health crisis. But I’m looking forward to starting traveling again.

As for my colleagues…we do meet about three to four times a year on average. So, we do have time to interact. The meetings we have are not just work meetings but also social gatherings. Because feeling happy to work with somebody is more than just about the work aspects. It’s also about getting along personally.

You are observing the space from an interesting perspective because you’re in a very high-profile project. You know a lot of teams, and you deeply care about technology.

Many teams are staffed with knowledgeable people. They’re very committed, but the output can vary significantly. So in your opinion, what makes some of these teams very successful? Why can they deliver better than others?

What’s probably a common bidder to all teams is that they are deeply interested in the matter. You don’t get to a position where you are working at this level without it being part of your soul.

I think the difference between incredibly productive teams and teams that are a bit slower is that the product teams have a goal to work towards. And the goal is very concrete.

I see a lot of initiatives that are set out to create something very abstract. Something that doesn’t have an intrinsic value. Or something so far fetched that even taking the first step towards that goal feels insignificant. Because of that, people will postpone that first step and all subsequent steps.

So, I think it’s good to have reasonable, small, and incremental goals to work towards. Such that the goal is always attainable.

And that’s a mark of a good project leader. Setting out those goals and always making sure that we’re not wearing off the course while still maintaining the individual developer’s core interests.

What other specific areas for improvement you see when it comes to Bitcoin? And which other projects intended to solve those issues are out there?

Lightening has the aspect of payments pretty nicely covered. It offers the ability to exchange an amount of currency for goods and services in a real-time fashion.

If we want to go beyond that, the general idea of off-chain contracts such as Lightning, or layer two solutions as they’re sometimes called, applies to all possible interactions with the blockchain, which can serve as a foundation for off-chain contracts on top of it. So, when it comes to Bitcoin…Bitcoin is a value transfer network. You can do some other things like the Omni layer added asset tracking to Bitcoins.

So there is a proposal by some, called RGB, that attempts to take the Omni layer that allows you to virtualize assets on the Bitcoin blockchain and move that onto Lightening. So, you could have an exchange for virtual goods in real-time for payments.

And the same is true for another one of our projects, called Liquid, where we have similar capabilities to track virtualized assets. There, we have the addition of confidentiality mixed into the assets, both in value and the type of asset we’re following. So that’s something that we’re working towards as well.

And if we leave Bitcoin aside, we can look at what other blockchains do. As far as I know, we can build similar layers like Lightning on top of other blockchains to increase the scalability and usability because of the real-time settlements. And to increase the privacy by basically not leaving a permanent trace on the blockchain itself but by aggregating multiple operations into one.

What some of these solutions have already been working on, for example, are the zero-knowledge roll-ups. This is an example of where you have a small footprint on the blockchain itself. You’re presenting any number of interactions between parties of that contract.

For the technically interested listeners, the RGB team has quite a bit of traction in Switzerland. We are delighted to report that. It looks like some industry participants are looking seriously at an RGB implementation for certain assets. So that’s very exciting.

I’m meeting every once in a while with the team to see how we can make RGB a reality based on the technology we have built-in Lightning. I think there’s not much use in reinventing the wheel when we can adapt an existing one.

What is essential for you when it comes to teamwork? What kind of values or traits are you looking for in people that you’re working with?

This team, in particular, is made of very independent participants. We pick our tasks to work on next. We do coordinate whatever needs to be done together. But everybody is very independent.

That’s something that gives you a feeling of ownership. And, of course, also a sense of pride about what you’ve achieved. So, it’s a very self-managed style of working, which I appreciate. And that’s thanks to our team lead.

You mentioned that you had an intern before, so what does somebody has to have to join your team as an intern?

They need to be interested and ready to work. We don’t have any particular requirements except that you should be motivated and independent. We do a bit of handholding, but we prefer somebody who is very bubbly and comes up with your questions and tasks to do.

Why do you think Switzerland was one of the first places where the Bitcoin community gathered?

A little-known fact is that the first-ever Bitcoin meetup was in 2011, here in Zurich. And that was kind of the first real-life meeting in the Bitcoin community.

I think the Swiss people are quite open to the idea of Bitcoin as money because Bitcoin is about individual freedoms. Bitcoin is about individual control, about self-sovereignty. I think that meshes very nicely with the Swiss mentality.

I decided to become Swiss a couple of years ago after noticing that despite being German on the passport, I do not feel German at all.

What was your involvement in the Swiss legislation regarding transactions in a ledger, based on which they can be used in any legal proceeding and in a court of law to document ownership change?

During the drafting phase, I was the technical advisor for the working group who worked on that proposal. It was quite an interesting situation, being surrounded by lawyers and being the only guy who wasn’t wearing a suit.

I found it productive to be able to talk to the legislative side of things. With my limited knowledge about legislation, I could still provide answers to most of the questions they had. And most importantly, my goal was to make sure that the ledger is not defined too narrowly.

Because if we would define it in a way limited to blockchains or DLTs we have today, then we would be back at the discussion table in half a year. Because this space moves way quicker than any legislation can.

So, we pushed very hard to externalize the description of the guarantees and the description of the technical side of the ledger into a separate document. It would then be presented to the issuer, and the issuer would, by choosing one or the other, accept or decline the trade-off step that the ledger would provide.

So, it’s the asset issuer’s responsibility to make sure that the ledger is technically sound. And that hopefully will keep us flexible enough to react to future developments in the space,

What are your top three pieces of advice that you could give to a potential founder on how to run a business?

Be selective about what projects you pursue. Make sure they are feasible and not some pipe dream.

Be selective about which people you let work on this project. People interested in working on it will make time to work on it, and you won’t have to micromanage.

And thirdly, always lay out the roadmap so that goals are achievable and not something that is too far to even take the first step towards.