Top 50+Blockchain Intermedio Interview Question-Answer

Blockchain: A definition

A blockchain is a growing list of records, called blocks, that are linked together using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree). The timestamp proves that the transaction data existed when the block was published in order to get into its hash. As blocks each contain information about the block previous to it, they form a chain, with each additional block reinforcing the ones before it. Therefore, blockchains are resistant to modification of their data because once recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks.

Blockchains are typically managed by a peer-to-peer network for use as a publicly distributed ledger, where nodes collectively adhere to a protocol to communicate and validate new blocks. Although blockchain records are not unalterable as forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.


How it works: Blockchain explained

Using the bitcoin system as an example, here’s how blockchain — also known as distributed ledger technology —  works:

Read more latest technologies MCQs

  1. The purchase and sale of bitcoin is entered and transmitted to a network of powerful computers, known as nodes.
  2. This network of thousands of nodes around the world vie to confirm the transaction using computer algorithms. This is known as bitcoin mining. The miner who first successfully completes a new block is rewarded with bitcoin for their work. These rewards are paid with a combination of newly minted bitcoin and network fees, which are passed on to the buyer and seller. The fees can rise or fall depending on the volume of transactions.
  3. After the purchase is cryptographically confirmed, the sale is added to a block on the distributed ledger. The majority of the network must then confirm the sale.
  4. The block is permanently chained to all previous blocks of bitcoin transactions, using a cryptographic fingerprint known as a hash, and the sale is processed.

The concept of blockchain technology first appeared in academic papers from 1982, in a dissertation discussing “the design of a distributed computer system that can be established, maintained, and trusted by mutually suspicious groups.” But it was a 2008 paper by the pseudonymous Satoshi Nakamoto titled “Bitcoin: A Peer-to-Peer Electronic Cash System” that brought an academic theory into real-world use

Q.1 Blockchain is a distributed______.

   A. Server

   B. Ledger

   C. System

   D. Computer

Ans : Ledger

Q.2 _ are a set of rules that verify and add transactions to a blockchain.

   A. Blocks

   B. Consensus mechanisms

   C. Mathematical formulas

   D. Laws

Ans : Consensus mechanisms

Q.3 What does C stands for in CAP theorem?

   A. Computation

   B. Capacity

   C. Correct

   D. Consistency

Ans : Consistency

Q.4 Bitcoin is a public, permisionless blockchain.

   A. True

   B. False

Ans : True

Q.5 Miners are rewarded with tokens like bitcoins and ether for mining the blocks.

   A. True

   B. False

Ans : True

Q.6 What is the total number of bitcoins that can ever exist?

   A. 21 millions

   B. 21 billions

   C. 1 millions

   D. 100 millions

Ans : 21 millions

Q.7 Which type of blockchains are controlled by a particular person or organization?

   A. Private

   B. Public

   C. Personal

   D. Consortium

Ans : Private

Q.8 _ is a process of verifying transactions, bundling them into blocks, and adding those blocks to the blockchain.

   A. Mining

   B. Digging

   C. Filtering

   D. Coding

Ans : Mining

Q.9 A peer to peer network of autonomous computers is a __.

   A. Distributed System

   B. Client

   C. Server

   D. Super Computer

Ans : Distributed System

Q.10 _ contains hash of previous block and all the important information required by the block.

   A. Block Header

   B. Block Metadata

   C. Chain

   D. Block Footer

Ans : Block Header

Q.11 Permissioned blockchains usually use PBFT algorithms.

   A. True

   B. False

Ans : True

Q.12 The Proof of Elapsed Time (PoET) concept was developed by __ in early 2016.

   A. Intel

   B. Apple Computer

   C. Microsoft

   D. IBM

Ans : Intel

Q.13 _ relies on exchange of messages among nodes that follow a distributed protocol to come to an agreement.

   A. Proof of Work

   B. Proof of Stake

   C. PBFT Algorithm

   D. Proof of identity

Ans : PBFT Algorithm

Q.14 Which release of Ethereum will have Proof of Stake Consensus algorithm.

   A. Juniper

   B. Serenity

   C. Constantinople

   D. Casper

Ans : Serenity

Q.15 Which consensus algorithm requires the users to have a stake in the blockchain?

   A. Proof of Work

   B. proof of stake

   C. proof of identity

   D. proof of elapsed time

Ans : proof of stake

Q.16 In private blockchains, you can create your own tokens for transactions.

   A. True

   B. False

Ans : True

Q.17 Consensus algorithms must be fault tolerant.

   A. True

   B. False

Ans : True

Q.18 Ether tokens can be used to buy Gas.

   A. True

   B. False

Ans : True

Q.19 A smart contract is a business logic or a legal agreement that is coded using a programming language.

   A. True

   B. False

Ans : True

Q.20 Oracles provide a trustless way of getting external information.

   A. True

   B. False

Ans : True

Q.21 __ are systems that provide external data sources to smart contracts.

   A. True

   B. False

Ans : True

Q.22 __ are systems that provide external data sources to smart contracts.

   A. Fortunes

   B. Tokens

   C. Routers

   D. Oracles

Ans : Oracles

Q.23 What are the main tokens used as digital currency in Ethereum?

   A. Bitcoin

   B. Gas

   C. Litecoin

   D. Ether

Ans : Ether

Q.24 Which type of cryptography uses only private keys?

   A. Symmetric

   B. Asymmetric

   C. Private

   D. Public

Ans : Symmetric

Q.25 _ are the set of the rules and regulations that control the working of a blockchain.

   A. Laws

   B. Governance

   C. Protocols

   D. Consensus

Ans : Governance

Q.26 What are the two types of forks?

   A. Simple,Complicated

   B. Temporary, Permanent

   C. Alive, Dead

   D. Hard Fork, Soft Fork

Ans : Hard Fork, Soft Fork

Q.27 Which type of cryptography uses two cryptographic keys?

   A. Secure

   B. Private

   C. Dual Key Cryptography

   D. Asymmetric

Ans : Asymmetric

Q.28 Public blockchains are goverened by communities.

   A. True

   B. False

Ans : True

Q.29 A hash function should produce different output strings for the same input data.

   A. True

   B. False

Ans : False

Q.30 Ethereum is a programmable blockchain.

   A. True

   B. False

Ans : True

Q.31 _ are a collection of key-value pairs, with state changes recorded as transactions on the ledger.

   A. Assets

   B. Transactions

   C. Tokens

   D. Blocks

Ans : Assets

Q.32 _ is a javascript library that allows you to interact with Ethereum.

   A. Angular

   B. web3.js

   C. JQuery

   D. D3.js

Ans : web3.js

Q.33 You can have private test networks in Ethereum.

   A. True

   B. False

Ans : True

Q.34 Which of the following blockchain is used for non currency, industrial application?

   A. Hyperledger

   B. Ethereum

   C. Bitcoin

   D. Litecoin

Ans : Hyperledger

Q.35 What are the two types of accounts in ethereum?

   A. Public, Private

   B. Programmable, Non Programmable

   C. External, Contract

   D. Secure, Open

Ans : External, Contract

Q.36 __ is a way of verifying the authenticity of digital messages and documents over the internet.

   A. Digital Imprint

   B. Password

   C. Digital Signature

   D. Fingerprint

Ans : Digital Signature

Q.37 What are the tokens used as computational fee in ethereum blockchain?

   A. Dollars

   B. Ether

   C. Gas

   D. Bitcoin

Ans : Gas

Q.38 Which release of Ethereum will have Proof of Stake Consensus algorithm.

   A. Juniper

   B. Serenity

   C. Constantinople

   D. Casper

Ans : Serenity

Q.39 What are the two main types of cryptography?

   A. Strict, Not strict

   B. Symmetric, Asymmetric

   C. Local, Global

   D. Private, Public

Ans : Symmetric, Asymmetric

Q.40 _ is a software defining assets, and the transaction instructions modifying those assets

   A. Chaincode

   B. Transaction code

   C. Byte code

   D. Asset code

Ans : Chaincode

Q.41 Hyperledger platform was developed by __.

   A. Linux Foundation

   B. Microsoft

   C. IBM

   D. IBM

Ans : Linux Foundation

Q.42 Which consensus algorithm requires a complex, computation intensive mathematical problem to be solved.

   A. PBFT

   B. PoS

   C. PoW

   D. PoI

Ans : PoW

Q.43 What are the two types of accounts in ethereum?

   A. Public, Private

   B. Programmable, Non Programmable

   C. Secure, Open

   D. External, Contract

Ans : External, Contract

Q.44 Which type of cryptography is also called public key cryptography?

   A. Asymmetric

   B. Symmetric

   C. Public

   D. Dual Key Cryptography

Ans : Asymmetric

Q.45 Ethereum is a public blockchain.

   A. True

   B. False

Ans : True

Q.46 Nodes are independent computing units of a distributed system.

   A. True

   B. False

Ans : True

Q.47 Hyperledger Fabric is a private blockchain.

   A. True

   B. False

Ans : True

Q.48 In __ mechanism, the miner is selected based on reputation built over time.

   A. Stake based

   B. Elapsed Time

   C. Reputation based

   D. Power based

Ans : Reputation based

Q.49 What is the Consensus algorithm used by Ethereum?

   A. Dagger hashimoto

   B. Eth Consensus

   C. Ethash

   D. Ethereum Hash

Ans : Ethash

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