Low-hanging fruit for the crypto community – Ethereum Meetup Berlin January 2017

Even though the scheduled talk about “Decentralised, Direct Democracy & Multidimensional Monetary System” didn’t take place, the January meetup at the Ethereum HQ in Berlin didn’t lack interesting topics and speakers. The night was comprised of four talks and went for almost three hours.

In my recap I want to skip the first talk about deckard.ai, because this development tool is not primarily focused on the crypto-space and therefore not really related to the topic of this blog. However you can watch a recording of the talk here: https://www.youtube.com/watch?v=Vgx56cpw-8U


Yann Levreau

The second talk was an update on the progress of the smart contract development enviroment Remix held by Ethereum’s own Yann Levreau. Remix was just last week merged with browser-solidity and focuses on giving fast feedback to developers while writing smart contracts in solidity.

The enviroment runs in the browser and lets you choose how to connect with an Ethereum node. The options are Javascript virtual machine (local and in memory), providers like Mist or Metamask and last but not least a node at localhost. A great strength of this tool is the ability to replay a contract execution and go through it step by step. Executed statements will be highlighted and state changes in the contract are displayed, which helps a lot in debugging smart contracts.

The developent enviroment doesn’t contain a testing framework and Yann Levreau recommends the use of either Embark or Truffle for this end. The speaker demoed how to use Remix when developing a frontend for dapps and hinted that project management tools might be on the roadmap for Remix in the future.


Ligi esPass

esPass stands for electronic smart pass and aims to bring the benefits of cryptographic tokens to the realm of tickets. Most tickets nowadays use QR- or barcodes. These codes just represent passwords that gains us access to concerts, conferences, airplanes, etc. They come with the big drawback that they can be copied. This constitutes a big problem when tickets need to be resold. There is no way for a potential buyer to verify that not other copies of the same ticket are in existence and that he will be the first person to try to enter with that given code. Luckily blockchains provide a solution for exactly this kind of problem. Presenter Ligi said that ticket systems therefore represent low-hanging fruit for the crypto community.

The creator of esPass put a lot of thought into the question of how to onboard users that don’t have experience in how to use public/private keypairs or digital currencies. His tenet is that the esPass tickets should gracefully degrade to the experience that users are already used to. That means that users who are not interested in the benefits of a blockchain-based ticket should just be able to print a PDF with a QR-code.

As the backend for esPass Ligi chose Ethereum. One of the reasons for this decision is ethereum’s determination to switch to POS in the not so distant future and thus become one of the most enviromentally friendly blockchains. However a problem with this is the lack of a proper light-client for ethereum, however progress on the light-client seems to be made and we can hope for a release sometime in the not too distant future.

Integrating ZCash with Ethereum

Dr. Christian Reitwiessner

As the last part of the evening Christian Reitwiessner gave a in promptu Q&A session about the effort to implement zkSnarks on the ethereum blockchain. However much better than any recap that I could write on this topic is his own blog post on the topic, which I highly recommend.

Videos of the talks are available on Adjy Leaks channel. However as of the time of writing there is no sound for the Remix and esPass talks, however Ryan indicated that he might reupload it later.

Q&A session with Fabian Barkhau of Storj.io

About 10 people met today at Ethereum’s Berlin offices to listen to Fabian Barkhau, a core developer of storj.io. Storj is a decentralized market place for disc storage that might soon allow us to lend out idle disc space in exchange for cryptocurrency. Fabian’s task at the company is to develop a publish/subscribe system which will be used to communicate offers and bids for disc space between users.

PubSub systems are typically centralized systems, where users will post their bids and offers to an intermediary broker. The challenge is to achieve the same functionality without making use of a centralized hub. Fabian reported that there is currently no good libary for a peer-to-peer pubsub system, even though lots of projects in the decentralized systems space have need for one. Even worse, there are very few research papers about this topic. The best paper Barkhau discovered and decided to base his work on is Quasar: A Probabilistic Publish-Subscribe System for Social Networks.

Barkhau has implemented the Quasar pubsub system in a concise python program. The only point in which Barkhau’s implementation deviates from the system described by the paper is that it adds a proof-of-work component. This is an effort to prevent possible network spamming attacks.

After the speaker gave the introduction to pubsub systems and Quasar, he opened the event up for questions. The audiences’ questions moved the focus away from the pubsub to storj in general.

One attendee asked about how payments are handled in storj. Barkhau explained that the payment aspect is currently still in development. The plan is to issue Storjcoin on the counterparty network (which is implemented on top of the bitcoin blockchain). Payments for disc storage will be made in Storjcoin which can be purchased on the usual exchanges for digital currencies.

Discussion after the Storj Presentation

Discussion after the Storj Presentation

The payments will move through payment channels (similar to the ones used in the lightning network). The use of payment channels means that most micropayments for disc usage can be made without having to write to the blockchain, thus saving blockspace and transaction fees.

Another question that came up is, how can it be ensured that the providers of disc space are indeed saving the files they are supposed to save. Barkhau answered that storj implements auditing of storage-providers. During audits the auditor passes a seed to the storage provider, which the provider uses to generate a cryptographic proof that he still has all the data.

In the end the discussion came back to the decentralized pubsub system. Barkhau stressed that he would welcome it, if there was one common, “standard” decentralized pubsub that would be used not only by storj but by other projects as well.

If you are interested in decentralized systems and live in Berlin make sure to subscribe to the meetup group Decentralized Hack & Learn to be notified about the next event. Thanks to Cristian for organizing this.

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