CBDH Sample Questions Answers

References:

A tokenless ledger refers to a distributed ledger that doesn’t require a native currency to operate. Generally, in a private blockchain tokens are not needed due to resources controlled by one party.

X509 certificates are used in Hyperledger Fabric. An X.509 certificate is any certificate under the X.509 specification standard for public key infrastructure and Privilege Management Infrastructure (PMI). The X.509 provides standardized formats for: Attribute certificates Public key certificates Certificate revocation lists Certification validation algorithms

References:

Peer-to-Peer essentially uses data sharing, hosting hardware owned by many not few, fault tolerant, secure, lower performance. It’s common way to share files—a good example was Napster. Peer-to-peer (P2P) file sharing is the distribution of digital media such as software, videos, music, and images through an informal network in order to upload and download files. Typically, P2P software enables users to select which files to share. These files are indexed on a central server, making them available for other users to find and download.

An endorser executes and endorses transactions. The endorsing peers take the role of endorsing transactions before they are ordered and committed as per the policy defined in Chaincode.

Assets in Hyperledger Fabric are represented in JSON or Binary. Assets are represented in Hyperledger Fabric as a collection of key-value pairs, with state changes recorded as transactions on a Channel ledger. Assets can be represented in binary and/or JSON form. Dont get confused of how Fabric is developed and how assets in chaincode are deployed

References:

There are two parts: 1. Business Network Archive which essentially captures the core data in a business network, including the business model, transaction logic, and access controls, the Business Network Archive packages these elements up and deploys them to a runtime. Business Network Archive files are stored as “.bna” files. AND 2. Composer Playground which is web-based tool allows developers to learn Hyperledger Composer, model out their business network (domain), test that network, and deploy that network to a live instance of a blockchain network. The playground keeps the development model in browser storage, allowing them to be easily uploaded or downloaded.

Validity rules (validation) state how the user and the transactions will be validated. This is predetermined by the consensus algorithm.

Client Node: That initiates the transaction 2. Peer Nodes: Commits Transaction & keeps the data in sync across the ledger 3. Ordered: They are the communication backbones and responsible for the distribution of the transactions

This web-based tool allows developers to learn Hyperledger Composer, model out their business network (domain), test that network, and deploy that network to a live instance of a blockchain network. The playground keeps the development model in browser storage, allowing them to be easily uploaded or downloaded. The playground also allows for CRUD (create, read, update, delete) operations to be performed on asset transactions which are created and logged. Composer playground offers a repository of sample business networks that can provide a base for building your own business network.

When the Init, Invoke or Query function of a chaincode is called, the fabric passes the stub *shim.ChaincodeStub parameter. This stub can be used to call APIs to access to the ledger services, transaction context, or to invoke other chaincodes.

References:

REST API support and integration capabilities: A LoopBack connector for business networks has been developed that exposes a running network as a REST API which can easily be consumed by client applications and integrate non-blockchain applications. This allows for easier front end application development without having to know the network internal application structure.

To create a network according to an organization's structure, and to bootstrap a channel, we will need to generate the following artifacts: A genesis block, containing organization-specific certificates that serve to initialize the Fabric blockchain. Channel configuration information. Anchor peer configurations for each organization. An anchor peer serves as a fulcrum within an organization, for cross-organization ledger syncing using the Fabric gossip protocol.

Hyperledger Sawtooth is a modular platform for building, deploying, and running distributed ledgers. Hyperledger Sawtooth includes a novel consensus algorithm, Proof of Elapsed Time (PoET), which targets large distributed validator populations with minimal resource consumption.

The application is bootstrapped knowing about a group of peers which are trusted by the application developer/administrator to provide authentic responses to discovery queries. There is the bootstrap of a peer network, during which policies, system chaincodes, and cryptographic materials (certs) are disseminated amongst participants, and the bootstrap of an ordering network. The bootstrap of the ordering network must precede the bootstrap of the peer network, as a peer network is contingent upon the presence of an ordering service. A network need only be “bootstrapped” once.

References:

Membership services provide identity, privacy, and confidentiality to the network. Abstraction of an architecture for membership operations.

References:

Hyperledger Fabric provides a Node.js and a Java SDK to facilitate network communications functionality.

/chaincode is the endpoint used for deploying, invoking, and querying chaincode. Which operation you perform is controlled by the body of the request that you send. /registrar allows you to enroll users.

References:

SOLO is the Hyperledger Fabric ordering mechanism most typically used by developers experimenting with Hyperledger Fabric networks. SOLO involves a single ordering node and Note Development Only.

Simple key-value pairs - LevelDB is the default and is particularly appropriate when ledger states are simple key-value pairs. A LevelDB database is closely co-located with a network node – it is embedded within the same operating system process. CouchDB is a particularly appropriate choice when ledger states are structured as JSON documents because CouchDB supports the rich queries and update of richer data types often found in business transactions. Implementation-wise, CouchDB runs in a separate operating system process, but there is still a 1:1 relation between a network node and a CouchDB instance. All of this is invisible to chaincode.

Answer: https://hyperledger-fabric.readthedocs.io/en/release-1.3/ledger/ledger.html

Endorsing Peer Endorser peer Peers can be marked as Endorser peer (i.e. Endorsing peer). Upon receiving the “transaction invocation request” from the Client application the Endorser peer Validates the transaction. Check certificate details and roles of the requester. Executes the Chaincode (Smart Contract) and simulates the outcome of the transaction. But it does not update the ledger. At the end of the above two tasks the Endorser may approve to disapprove the transaction. As only the Endorser node executes the Chaincode (Smart Contract) so there is no necessity to install Chaincode in each and every node of the network which increases the scalability of the network.

State Based y default, endorsement policies are specified for a channel’s chaincode at instantiation or upgrade time (that is, one endorsement policy covers all of the state associated with a chaincode). However, there are cases where it may be necessary for a particular state (a particular key-value pair, in other words) to have a different endorsement policy. This state-based endorsement allows the default chaincode-level endorsement policies to be overridden by a different policy for the specified keys.

References:

Rootcert, tcert and ecert. As The CA (Fabric CA by default) issues a root certificate (rootCert) to each member (organization or individual) that is authorized to join the network. The CA also issues an enrollment certificate (eCert) to each member component, server-side applications and occasionally end users. Each enrolled user is granted an allocation of transaction certificates (tCerts). Each tCert authorizes one network transaction.

References:

Distributed Ledger manages the world state and the transaction log in the blockchain. The world state is defined as the state of all transactions on the Blockchain, where all nodes agree that all blocks on the Blockchain are at the same state. It implements three key attributes. It efficiently calculates the cryptographic hash of the entire dataset of each block. It efficiently transmits a minimal “delta” changes to the dataset, when a peer is out of sync and needs to “catch up”. It minimizes the amount of stored data required for each peer to operate.

There is a new open-source application development framework, which simplifies the creation of Hyperledger Fabric blockchain applications, thus reducing the time and complexity of development. The tool aims at helping users to create blockchain applications based on Hyperledger Fabric without needing to know the low-level (Go Programming) details involved in blockchain networks.

References:

Management is not correct. The Hyperledger Project consists of the following Infrastructure - Ecosystems that accelerate open development and commercial adoption Frameworks – A portfolio of differentiated approaches to business blockchain frameworks developed by a growing community of communities Tools - Typically built for one framework, and through common license and community of communities approach, ported to other frameworks hyperledger.org.

Getting started- Writing chaincode you will want to make sure that you have the Go programming language installed and correctly configured. Make sure that a directory is created for your chaincode application as a child

Decentralized Autonomous Organization (DAO) can be thought of as a corporation run without any human involvement under the control of an incorruptible set of business rules. A DAO can also be seen as the most complex form of a smart contract, where the bylaws of the decentralized organization are embedded into the code of the smart contract, using complex token governance rules.

A CouchDB database is closely co-located with a network node and it is embedded within the same operating system process.

References:

Users can use chaincode (for business rules) and membership service (for digital tokens) to design assets, as well as the logic that manages them. There are two popular approaches to defining assets in most blockchain solutions: the stateless UTXO model, where account balances are encoded into past transaction records; and the account model, where account balances are kept in state storage space on the ledger. Each approach carries its own benefits and drawbacks. This blockchain fabric does not advocate either one over the other. Instead, one of our first requirements was to ensure that both approaches can be easily implemented with tools available in the fabric.

Hyperledger is an open source project that came out of the LF and was created in order to help advance cross-industry blockchain technologies. It's a global open source collaboration involving leaders from numerous industries.