Comparing Distributed Ledgers by Game of Thrones use case — Hyperledger (Fabric + Composer)
This is the eigth part of our series “Comparing Distributed Ledgers by Game of Thrones Use Case”. To find out more about the series and the other articles of it, check out our intro article!
Our ledgers are hot, our ledgers are smart, and now our ledgers are hyper! Welcome to the hyperledger part of our series.
Hyperledger is an umbrella project hosted by the Linux Foundation. In their terms “it is an open source collaborative effort created to advance cross-industry blockchain technologies”. In December 2015 it started and received contributions from big companies like IBM or Intel.
Rather than a single distributed ledger technology, Hyperledger is a hub for business blockchain frameworks and tools with variant goals. Take a look at the following picture from their official website, to get a feel for the “Hyperledger Greenhouse”:
One of the most popular combinations are Hyperledger Fabric with Hyperledger Composer. This combination is what we used for our game of thrones use case.
Hyperledger Fabric got a lot of recognition because it was initially contributed by Digital Asset and IBM. It has a modular architecture with interchangeable components such as consensus and membership services. While Fabric gives us the bricks and the nails for a great project, composer gives us hammer and screwdriver for efficient development.
Technical overview of Hyperledger Fabric:
Hyperledger Fabric is a permissioned blockchain framework. It facilitates smart contracts in the form of chaincode, which function as the business logic. Admins of the Fabric network can instantiate and later update existing chaincode.
A process of 3 phases exists to add a transaction to the ledger: Endorsement, Ordering, and Validation.
* Endorsement: Endorsing peers execute the chaincode to simulate the transaction, and sign it if valid. The associated endorsement policy specifies how many signatures of endorsing peers are needed.
* Ordering: In this phase it is determined in which order endorsed transactions get added to the ledger by putting them into a batch/block.
* Validation: Committing peers make sure that the endorsement policy is met, and check the validity of the simulated transactions.
To fully understand the process, we recommend to check out the illustrated examples on the official websites here (point 2 ) or here (section Consensus in Hyperledger Fabric).
As Hyperledger fabric is a permissioned blockchain, it is distributed across its members. A member is typically a company. Each company manages its own Certificate Authority, to issue and authenticate public-key certificates inside its own structure. The certificates are needed for the endorsing and committing peers.
For the ordering service in the ordering phase, any ordering logic can be used as Fabric is intended as plug-and-play. Out of the box Fabric uses Kafka as its ordering service.
Fabric is meant for business applications. A lot of business applications need to work with confidential data, and there’s a need for role based access control. Fabric successfully enables this, as access to transactions and state can be restricted to specific roles or identities. If needed, only holders
of specified roles can read or write particular data.
To enable confidential communication or exchange of value between two companies, there’s the possibility of creating a private channel between those parties. This way, a subset of parties inside a blockchain network can share channels, while other members do not have access to those.
Implementation:
To see the source code of our implementation, head over to our GitHub.
Disclaimer: Our research was done in July 2019, when Composer was still supported.
For our game of thrones idea we used Hyperledger Fabric in combination with Hyperledger Composer as mentioned above. Furthermore, we made use of the corresponding playground, which makes it possible to test chaincode without setting up the network of nodes yourself.
To create a skeleton of a so called business network, we used the Yeoman generator. In addition, we made use of the npm composer module. With this npm module, one can create the .bna file that is needed for the playground, and with its help one can also instantiate a local business network and interact with it.
For the chaincode itself, the developer needs to write ‘model’ files ending with .cto, and logic files written in javascript. Models use a special syntax to describe assets and the corresponding transactions. The logic defined in javascript describes programmatically how the functions defined in the model interact with the assets.
As unfortunately all of this provides a fair bit of redundancy, minor bugs can happen easily (at least we had some issues). Once the logic was written, we compiled it with the composer modules to a .bna (business network application) file, which we could upload to the playground. There we made our initial tests to see if Daenerys Targaryen receives the respect she deserves.
For automated unit tests, we used the embedded runtime, with which one can quickly test the code in a simulated Node.js blockchain environment. With the embedded runtime as well as the testing frameworks Mocha and Chai, we wrote our tests in javascript and executed them with NodeJS.
Pros and Cons
Pros:
- Big companies build solutions with Hyperledger
- Hypereledger is hosted by the Linux foundation
- Hyperledger Fabric was developed by IBM, a strong team
- Lots of documentation and tutorials
- Role based access control
- Privacy
Cons:
- theory more complicated compared to other DLT’s
- coding is complicated, lots of code needed for simple logic and new syntax
- setup of the network and its maintenance are complicated
- Not that decentralized, as only signatures of validator/committing peers are important
- There is no true consensus if Kafka is used. That means there isn’t enforced, democratized, and cryptographically secure voting between parties.
- As of the 29th August 2019, Hyperledger Composer is officially deprecated.
Special thanks to the Linux foundation for hosting the Hyperledger umbrella project!
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