I am new to the area of DLTs or "blockchain" and I am trying to create an application on top of Hyperledger Fabric. Before I describe my use case, I need to mention that due to my use case's nature I need a private & permissioned "blockchain" which justifies the choice of Fabric (I am aware of other platforms e.g. Corda, private Ethereum, but Fabric seems to match my use case better).
Use Case
My use case consists of two different types of participants. A number of organizations (which upload and share information about individuals on the distributed ledger) and a client who can query information about an individual.
The client should not be able to see the transactions uploaded by the organizations and will not have write rights on the DL. He has read-only rights. Moreover, the organizations trust each other and there is also a level of trust between them and the client.
Design thoughts
Based on what I've read, I was thinking of creating a DL network that includes all of these parties and use channels which, based on the documentation, can be used to create a grouping among a number of participants (the organizations in my case) thus "hiding" the transactions from the parties which are not included in this group (the client in my case).
However, later I read about chaincode (a.k.a. smart contracts) which:
can be invoked by an application external to the blockchain when that
application needs to interact with the ledger
which confused me since if the "blockchain" can be queried from an external entity, that probably means that the client should not be included in the trusted network.
Am I headed in the wrong direction (design-wise)?
Based on your description, Hyperledger Fabric channels sound like a good solution. You should also familiarise yourself with private data collections, as this is another way of hiding some of the data from some peers. Which option is best for your scenario will depend on how your datasets are structured, and whether you also need to keep the data private from the orderer.
Clients are not part of the network. They query the blockchain by connecting to a peer and then requesting data from that peer. They can then only access the data visible to that peer (which is stored locally by that peer). So, it is not possible for a client to access more data than is available to the peer the client is connected to.
In your example, you would have a "client" organisation, with at least one peer. This peer would be part of the network, and your client application would then connect to it for access to data on the ledger (typically using the Hyperledger Fabric Node SDK).
There are two types of chaincode in Hyperledger Fabric.
User Chaincode (often just referred to as "chaincode") is used to update the ledger for a channel, and is only installed on those peers which require it (i.e. endorsing peers). Since your "client" peer would not be an endorsing peer, it would not have access to the user chaincode for the channel.
System Chaincode which all peers have access to, provides (among other things) an interface to allow queries to be run against the ledger.
Related
Is it possible to have application level data privacy in Hyperlegder Fabric v2.2
We have the first network (as referenced in the fabric-samples) in place (Org1 and Org2 with peer0 and peer1 each). I am aware that data privacy can be ensured between 2 organizations using Private Data Collections. Looking at the case where peers in the network can run multiple user applications, consider that, there is app1 and app2 connected to the network via peer0 belonging to Org1. The cause for concern is that despite using private data collections, app1 could access the private data logged by app2 in Org1 private data collection. Is there a way in hyperledger fabric to ensure privacy between apps connected to the network via the same peer.
No, there is not.
You can develop your own authorization routines at smart contract level so that read related operations only return data to authorized users. This way you prevent other clients from accessing data through read operations, but the data is not protected from the peers themselves.
You can also encrypt your data in your client before sending it in a transaction. You can use your own Fabric certificate to encrypt data via ECIES or ECDH encryption schemas (or use any other encryption schema you want). But this way the contract is not going to be able to interpret your data. It will be only able to store it and return it...
In other cases, you may be interested in storing your data in your own private storage system outside Fabric and save only a hash of the data in the channel state as a proof that can be used later if necessary for whatever it is intended to.
These are things you can do to preserve privacy at user level. You can think of other solutions. But Fabric does not provide specific ways to do it. From a blockchain point of view, it is difficult to preserve data privacy at user-level while peers try to reach consensus over that data.
What happens if the ledger is taken out and attached to a new fabric network? especially in the below case
1 Fabric is used for storing confidential data among 3 parties.(via chaincode abac, chaincode multi ownership among 3 parties so there are three ledgers synced)
2 One party(party A) takes out the ledger and setup a new hlf behind and attaches the ledger to the new hlf and changes the chaincode in order to see all the data.......
In this scenario what can be implemented to prevent the party A from seeing the data.....isn't it true that the ledger is taken out so the ledger is just a chuck of file(impossible to function as long as it is not in the original HLF setup(the orginal hlf network.......even ip change blow up all the ledger and setting......).....
Look forward to your replies
For any given peer or orderer that is part of a Fabric "network", some person or entity will inevitably have physical access to the platform on which it is hosted. They will be able to physically read the ledger file(s) as well as the state database(s). So if they are not supposed to have access to the data, then you either need to encrypt the payloads at the application layer or you can use private data collections.
I have a web-based application for HR Employee management.
This application has many clients that login into the web app and uses the features.
I want to integrate this app into the blockchain. I want some of the data (compliance related, sensitive) to be recorded in the blockchain.
Data will be written to blockchain by my application only. My clients will only view the data.
What approach should I use?
a) Single Org (my app) with multiple peers (1 peer per client).
b) Multi-Org: Org1 = My app, Org 2 = Client 1, Org 3 = Client 2 .... n.
If any other approach please suggest.
Note: Individual Clients won't be sharing any data among themselves.
I want to use the hyper ledger fabric blockchain for only storing the information because it is immutable and tamper proof.
Even If I go with multi-org scenario, Both orgs will be added by me on servers managed by us. Will this cause trust issues in courts legally? Can I prove that data has not been tampered although all servers hosting blockchain are mine?
Based on your statement "Individual Clients won't be sharing any data among themselves", I would suggest 2 options based on the native capabilities of HLF, depending on whether all data in the transaction is private, or only a subset of the data.
No data is shared - one channel per peer, one peer/org per client OR one peer with multiple channels. In the multi-peer case, transaction data is only stored on the one peer which is a member of the channel. No other peers receive the data.
Some data is shared - one channel for all peers, one peer/org per client. In this case, a private data collection can be used to store private data. Transactions are stored on the ledgers of all peers, containing all the data in the case of the initiating peer, and only the public data plus the hash of the private data on all other peers.
Neither of these options provides data redundancy across peers, but since you didn´t state this as a requirement, I'm assuming this isn't a problem.
Since you state that you will be in control of all peers, the immutability guarantee doesn't count for much, as there is nothing to prevent you from rewriting the entire blockchain at any time. Despite this, such a solution would still be superior to a traditional database, since it would be immune to changes at an individual transaction level.
I am new to composer, and now practicing some of the tutorials and examples. But while doing this I can not understand some of the features, so here are the questions which I do not clearly understand:
Are queries restricted by .acl file (when, for example, we use them in rest server)?
Do the rules written in the .acl restrict some of the transactions which are allowed for certain participant to submit? (For example, for participantA it is not allowed to CREATE new participants, but what happens if participantA submits the transaction(which is allowed for him to submit)which creates another participant, will this transaction fail?
Could cards be created by rest api server?(I know that participants could be created using JS api, but is it possible to create and issue the identity for those participants through RestServerApi?)
What happens when PeerAdmin upgrade certain node to a new version? How do other nodes act in this case? Do they upgrade themself automaticly?(Also found that upgrade takes a lot of time(2-4 minutes) when deployed locally, whereas in browser for local connection it takes 3-4 seconds)
Does Hyperledger fabric allow some of the ledger data be stored in one private network, whereas other network connected to the private one would not store this part of ledger( or the data will be simply crypted)? The same question regarding the transactions: will the be executed on outer networks?
Yes Composer Queries (and therein, results) are subject to ACL restrictions or filters.
It will still fail due to ACL rule restriction. Once denied to create, always denied as that is the final operation (in this scenario). The actual transaction would fail.
Yes of course use POST /system/identities/issue REST endpoint (eg http://localhost:3001/api/system/identities/issue) - see an example here -> https://medium.com/#CazChurchUk/developing-multi-user-application-using-the-hyperledger-composer-rest-server-b3b88e857ccc
An administrator with PeerAdmin capability has responsibility to install new version on his peers (in his Org). The other Org peer Admins are responsible for theirs, that's how a blockchain consortium with different Orgs will work. They will agree the 'what' and when but will need to install the new version on own Org's peers, so the new version can be started on the same channel. Of course, there will be a difference between a Fabric infrastructure response time, and that of a web connection using local storage.
Channels in Fabric implement privacy. You can have one or more business networks on that channel (ledger), therefore transactions in that business network are private to that ledger. It is the client's responsibility to encrypt data or not. Hyperledger Composer can allow call one business network from another, on the same channel, or if permitted to do so, on different channels too - see https://hyperledger.github.io/composer/latest/tutorials/invoke-composer-network
Hyperledger enables you to create participants (via chaincode) as well as Organisations (via fabric setup). In a supply chain or any process, how do you decide which one is an Organisation and which one is a participant.
From my understanding, all participants of same category should fall under one organisation.
But then I have another issue, will buyers also gonna have their own organizations?
Organizations on Hyperledger works like a Board of Directors, they vote in consensus inside your network, if you are the only one org then everything is auto approved by you, Ex. An upgrade in chaincode with new model.
Use case: Think about if we build a blockchain network for Banks, every institution will be an org and the participants are their respective clients.
It all depends on security and privacy factors.
let consider Maersk, If the network is setup within Maersk what's the purpose of hiding data within themselves ? untill and unless there is no trust within.
So if Data Availabilty > Data privacy, i'd go on creating Maersk as one Organization and all sub entity under them are Peers and one channel so that they can share data within and between them.
Now, what if someone other than Maersk entity needs to be involved? like fleet, shipping, delivery, Manufacturer etc, they are the separate Orgs as these Organizations don't need to share every data flowing in and out, they only require what they want to serve for Maersk.
There might be a case where each entity works separate and has their own rules and interaction with multiple other parties under a main entity. Then again you need to decide based on the data sharing ,Transparency, Availability between parties. if data is just available between one or two entity where does DLT concept comes in ? and how/where does consensus fit in ?!!
You need to keep all these factors over use case and decide upon creation of Org and Peer.
Correct me if i'm wrong