I am working on how to develop a blockchain app using Hyperledger Composer. Since I have just begun with Hyperledger Fabric so I am pretty confused over Some Points-:
1) What are assets, participants and transactions.
2) What is the meaning of the symbol '-->' used for some variable.
3) Why do we need .bna file.
I am new to this concept so please bear with me as I have tried with documentation but it confuses me even more.
An asset is anything of value, whether physical or virtual.
A participant is a person or organization participating (taking part) in the blockchain network.
A transaction is an operation submitted by a participant to modify the blockchain. It could be transferring or modifying the amount of an asset. It could be recording an event. In any case, it modifies or creates a value in the blockchain network's ledger (also known as world state).
Related
I have a problem with understanding why Hyperledger Fabric (HLF) uses blockchain structure.
I know that in Bitcoin blockchain structure ensures big security due to PoW algorithm and longest chain rule, but what are advantages of using a blockchain structure in HLF?
It seems to me that in Hyperledger Fabric, instead of the blockchain structure, there could be one transaction history log and network could work in the same way - I bet I'm wrong, but I haven't been able to find an explanation yet.
I would be grateful for the clarification of this issue.
I think a lot of questions you have in your mind comes from the overlapped definitions of DLT and blockchain.
DLT:
A DLT is simply a decentralized database that is managed by various participants. There is no central authority that acts as an arbitrator or monitor. As a distributed log of records, there is greater transparency – making fraud and manipulation more difficult – and it is more complicated to hack the system.
All of this could well be familiar because it’s written about the features of blockchain as well.
Blockchain:
Blockchain is nothing else but a DLT with a specific set of features. It is also a shared database – a log of records – but in this case shared by means of blocks that, as the name indicates, form a chain. The blocks are closed by a type of cryptographic signature called a ‘hash’; the next block begins with that same ‘hash’, a kind of wax seal. That is how it is verified that the encrypted information has not been manipulated and that it can’t be manipulated.
DLT platforms that are not blockchain provide immutability too, but it's just the way Hyperledger Fabric provides this characteristic which makes it a blockchain framework.
Every blockchain framework, be it the Ethereum, Bitcoin, etc all store the transaction information in blocks, where each block is linked to its predecessor by a hash and provides immutability.
Corda is very much similar to Hyperledger Fabric, but it is said to be both a blockchain and not a blockchain. Architecturally, it's very much similar to Hyperleder Fabric, but with only a key difference which makes Hyperledger Fabric a blockchain framework, and Corda a DLT.
I'll try to answer your question by emphasizing on the point that why Corda is not a blockchain.
Why is Corda a blockchain, and not a blockchain?
A Transaction in Corda is cryptographically linked (chained) to the transactions it depends on. Just like Bitcoin, but the range of concepts that can be expressed is far wider.
Transactions in Corda are processed by having each participant in the transaction execute the same code deterministically to verify the proposed updates to the ledger. Just like Ethereum, but the languages you can use are high-level and productive, like Java, rather than obscure ones like Solidity.
Transactions in Corda are shared only with those who have a need to know. Just like channels in Fabric but designed in from day one and fully integrated into the programming model.
Transactions in Corda are confirmed through a process of consensus forming using one of a range of algorithms, including Byzantine Fault Tolerant algorithms. Just like any other blockchain, but with the unique features that a Corda network can support multiple different consensus pools using different algorithms.
So, for all intents and purposes, Corda is a blockchain. And yet… there’s also an utterly critical difference.
Unlike the platforms mentioned above, Corda does not periodically batch up transactions needing confirmation — into a block — and confirm them in one go. Instead, Corda confirms each transaction in real-time. No need to wait for a bunch of other transactions to come along. No need to wait for a “block interval”. Each transaction is confirmed as we go.
Now coming onto your question why Hyperledger Fabric (HLF) uses blockchain structure? The answer is simply because they chose to.
References:
https://www.bbva.com/en/difference-dlt-blockchain/
https://cointelegraph.com/news/what-is-the-difference-between-blockchain-and-dlt
https://www.corda.net/blog/corda-top-ten-facts-7-both-a-blockchain-and-not-a-blockchain/
To keep the record immutable, Hyperledger Fabric uses blockchain structure. So by using Hyperledger Fabric, you can get an immutable record of all the transactions which is tough to temper with fraudulent activities.
Suppose you buy an valuable asset and you are the current owner of that asset. Now it is very hard for others to temper that records or change your ownership without your permission as Hyperledger Fabric uses blockchain structure to keep the record immutable.
What are the fundamental differences between the two? I come from an Ethereum background and am fairly new to Hyperledger Fabric. I've heard people talk about "channels" in the Fabric ecosystem and it sounds quite similar to the concept of sidechains. It'd be awesome if someone could clarify the differences between the 2 (if they exist).
Since Etherium is a token-based blockchain, my understanding of sidechains is that they allow tokens to be transferred between the main ledger and a "child" ledger (the sidechain). Since Hyperledger has neither a native token nor the concept of "child" ledgers, I don't think they are really analogous to channels.
Hyperledger channels allow for private communication between a subset of peers on the network. Only those peers on the channel receive transaction data for the channel. Even if separate channels are not required, a single channel must still be defined, then all peers communicate on this channel. In this way, there is no main ledger in Hyperledger, as each channel effectively acts as a separate ledger.
I have developed two participants in two different hyperledger composer networks(A and B). A and B have a common asset. Since the asset is common, both networks must be able to update the shared asset. I have developed the shared asset in A, and I want to update it by B. B can read the asset by following the hyperledger tutorial[1], and also it can invoke low level commands of hyperledger fabric by its APIs[2] but I do not know how B can update the shared asset.
if the business networks are on the same channel in the same Fabric network (not different Fabric networks), then you can use invokeChaincode (as referred to in that 1st tutorial) to do an update call that would be atomic (ie all update(s) occur, or none at all, in the transaction function). You need to read up more on invokeChaincode usage in that regard.
Beyond that, it becomes a complex question, such as business networks on different Fabric channels or, in different Fabric networks - suffice to say, it would not be atomic in that case.
We are building a solution and we are modeling a network using Fabric and Composer
Regarding "not" storing any personal data (GDPR complience) on the blockchain, we would like to hash/map the personal data so that a GUID och Hash is stored in the Ledger instead (Anonymized data)
Does Hyperledger provide any solution to solve this kind of issues (ie a distributed DB that is around the ledger peers for example?)
Or is this something that is needed to be implemented outside the Hypeledger network topology?
Prior to Fabric v1.1, you would need to provide the database yourself and then just write the hashes to the blockchain as normal transactions. There are people who do this today for database records as well as for documents (store the document outside and just write the hash and metadata to the blockchain).
In Fabric v1.1, there is an experimental featured known as "private data". With this feature, the actual state is kept local to the peers in a private state database and is not included in the actual blockchain itself. The ledger actually contains hashes of the key and value.
There are new chaincode APIs (Get/PutPrivateData) which are used to do this automatically for you. You can then either delete the data manually or use the DeletePrivateState function in chaincode to delete the actual records (the hash will stay on the channel ledger).
This feature is experimental in v1.1 so you will need to build the peer from source with -tags experimental.
Since this feature is experimental, it is not currently supported in Composer.
We will be hardening the feature as part of the 1.2 release which is under development
In Ethereum, we cannot define/add new responsibilities for miners unless we modify/change miners' code.
Question: In Hyperledger Fabric, can we define/add new responsibilities for/to miners by using system chaincodes? or the system chaincodes are only for certain purposes (e.g. defining policies, validation)?
edit: this edit is done after the 1st answer has been provided.
miner or nodes or peers or orderers
There is no mining or miners in Hyperledger Fabric.
As #Jworthington stated, there are no miners in Hyperlegder. You need to take a step back and understand the core difference between Public Blockchains (Ethereum) and Permissioned Blockchain (Hyperledger, Corda).
To be fair, calling Hyperledger a blockchain is a bit of a misnomer. It is a distributed legder, and does not require the action of miners to reach consensus.
Both platforms work with the concept of nodes, with differing functionality. They are both similar in that nodes host versions of the world state/ legder. In ethereum , you have miner nodes, which are full nodes, with the additional responsibility of validating transactions via Proof of Work. In Hyperlegder, nodes function either as clients (to connect with the Fabric network), peers ( copies of the world state, validate or endorse transactions) and Orderer.
When you write chain code, you craft the rules that dictate the validation of transactions by the orderer. This is installed on peers and instantiated on each of the channels. You install the chain code on peers you want to endorse transactions (using the Lifecycle System Chaincode).
Endorsers simulate and endorse transactions using the Endorsement System Chaincode (ESCC), while committer peers validate transaction using the Validation System Chaincode (VSCC).
Hope this helps.