In the context of HyperLedger Fabric I want to manually generate the private keys, then build and submit transactions. How can I do this?
I would like to do this in a very low level language, possibly C.
This is the analog of what I want in Sawtooth (in Python 3): https://sawtooth.hyperledger.org/docs/core/releases/1.0/_autogen/txn_submit_tutorial.html
Links and references are welcome.
Here's the Fabric transaction Flow : hyperledger-fabric.readthedocs.io/en/release-1.2/txflow.html
This explains all the necessary steps in depth. In fabric, we always have to generate private keys manually (Either through cryptogen tool or using CA) and then use these keys to invoke and order a transaction. As of now, Fabric provides SDKs in Go,Node,JAVA and Python to accomplish t he flow you're asking. Python and Go could come close to the low-level-language like C/C++ from the all available options.
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For the past few days i am trying to learn blockchain, more specifically in using hyperledger fabric
However, while i am quite familiar building centralized app, i am so new in grasp this whole new concept, and got some question in mind i haven't found answer, yet.
If its decentralized, does the script will run as desktop background process in every machine connected to the network through internet?
Since
no way it could be "decentralized" if its hosted on 3rd party server
blockchain platform seems could seamlessly write/read local files, which certainly not possible at the case of hosted in 3rd party server
existing blockchain application (i.e bitcoin) written for desktop (c++)
If it does desktop process, in the case of creating website interface to run the application, do we need API to communicate? And if so, how the API could be made to communicate between all machine in the network?
Moreover in the case of storing sensitive data like password, since its stored locally in every machine, does it means we will rely only on encryption being used? I assume common AES256 will work? Or need multi layer encryption (as in XMR) to make it harder for people trying to decrypt those sensitive information?
Any input is greatly appreciated. Thank you in advance!
I'll answer your questions for Hyperledger Fabric since that's what you tagged this post for.
Presumably the "script" you mean is chaincode, the blockchain back-end part of the decentralized application. It runs on endorsers (part of Fabric peers), specifically all endorsers that are specified in the endorsement policy and have installed the chaincode. The endorsement policy specifies how many endorsers need to agree for chaincode transactions to go through, i.e. 3/5. These peers can be hosted by multiple organizations in different places, that's why it's decentralized.
You need to use the Hyperledger Fabric SDK to communicate with your chaincode (get data, send transactions).
Decentralized apps don't really use user-password combo for identity management. Users have public/private keypairs which they need to keep locally. Only if you want to encrypt the private key you'd need a password for the user to decrypt it locally. You use the private key to sign transactions and to authenticate with the network (which determines your access rights, i.e. user vs admin)
I can recommend the Fabric paper as a learning resource
Also check out the docs, they cover many of your questions
I would recommend first taking a step back and finding out what are the best use cases for Web3 vs Web2. There are a number of projects that seem to have been shoehorned into using Web3 when they could have been created more quickly and efficiently using
Web2 technologies.
Ask yourself these questions before jumping on board the decentralized Web3 bandwagon:
Is an Immutable Ledger the Best Fit for Your Back-end?
Does Your Back-end Work Best as Decentralized Computing?
Do You Need Scalability or High Transaction Volumes?
Only when you understand the problem you are trying to solve, can you determine the best technologies for the job.
To help answer the above questions, you can use the following article as a resource: https://www.scalablepath.com/back-end/choosing-web3-for-software-project
we are wondering where can we find a production quality sample for HL Fabric? we have studied the samples included with official release and have found that:
the balance-transfer sample shows how to write a HL Fabric app and make transactions and queries on the chaincode but uses the cryptogen tool which is not recommended for use in production
The fabric-ca app on the other hand shows how to spin up a network without using cryptogen but does not show how to write an app that can then be used to do transactions, make queries, enroll new users and so on
So we are looking for a sample that combines the best of above two apps. Does such a sample exist? Writing an app to get the benefits of both turned out to be harder than we thought e.g., fabric-ca sample does not output any network-config which is needed by balance-transfer and we are facing difficulty figuring out what the network-config should look like in this case. Also we see conflicting code between node and typescript in balance-transfer (although both are javascript) etc.
In the latest master of Hyperledger Fabric, there is a new and much more detailed sample--the commercial paper.
The tutorial covers the whole lifecycle of a chaincode.
I am new to hyperledger and bit confused about hyperledger composer & nodejs api.
I saw using composer we can create assets, transactions, participants and chaincode and in last we have to archive it this all into .bna file and finally we deploy this chaincode into network using admin card
But at other end using NodeJs API we can also write chaincode by overiding init & invoke methods.
How can we relate these all.
The best way to think about this is the following:
1) Hyperledger Fabric v1.1 supports writing chaincode in two languages: Golang and JavaScript via Node.js
If you want to do all of the heavy lifting yourself, you can write straight chaincode.
2) Hyperledger Composer provides a higher-level model-driven language for developing smart contracts. It currently only allows deployment of these artifacts to Hyperledger Fabric. It also happens to support writing functions in JavaScript as well.
So if you want to start from a higher-level model-driven approach, Hyperledger Composer is the way to go. If you want to write all of the plumbing yourself or use very low-level chaincode features, then using chaincode itself is the way to go.
Moving forward, we are looking at a better way to move between the two and not force a decision / direction up front.
There is another option, we develop a framework called Convector to be in the middle of Composer (high abstraction, low control) and raw code (low abstraction, high control, therefore high risk). We open sourced it a few days ago. At WorldSibu we don't like loosing so much control over our code like with Composer but as Gari Singh was saying, doing all the heavy lifting for each project is crazy. It is like a Mongoose for Hyperledger Fabric. It may help to check it out.
It is also worth noting that, according to IBM, Composer is no longer recommended as a production solution, but only for prototyping. In HLF 1.3, chaincode can now be written in Go, Javascript and Java.
I'm wondering how you can get a hyperledger fabric smart contract to read from external API's ?
A service called oraclize (http://www.oraclize.it/) is used to do this operation in Ethereum blockchains - Is there anything similar for hyperledger fabric smart contracts or any workarounds?
In Hyperledger Fabric - smart contracts (the chaincode), could be implemented at the moment with either golang or Java, both of which are Turing complete and provides you with reach set of libraries and frameworks. Among which you can you any network library to get connected with external services, while you need to be extra cautious doing this to make sure your chaincode is deterministic (e.g. two independent executions of the same chaincode calling same external API will get same result back).
Riccardo from Oraclize here.
We are actually working on a Oraclize integration with Hyperledger.
I have been working on hyperledger fabric for some time. But I don’t understand where hyperledger composer comes in place . I do understand that it helps in visualizing the logic and transaction. But what I don’t get is how do you integrate it with fabric network? what does it create? Is it chaincode if not then what?
The Compose runtime is chain code that executes the business network archive artefacts created by the end-user.
Perhaps this will help?
https://blog.selman.org/2017/07/08/getting-started-with-blockchain-development/
The tech answer is that Hyperledger Composer is an abstraction layer over Hyperledger Fabric.
The practical answer is that it is awesome. Think how Angular and hundreds of other frameworks make web programming easier.
It is a framework where you can write your blockchain in Javascript and specify your data objects in an easy to understand text file. Throw in some querying, ACL stuff and pathways to use some nice opensource tools that let you do things like generate a Web API automatically and play around in a web environment without installing anything.
We are using it for the Integra Ledger Legal blockchain. (www.integraledger.com). I just spent the day working in it.