In this Blockchain Interview Questions blog, we have listed the most important Blockchain interview questions and answers that will set you apart in the interview process.
All the questions presented here are frequently asked in many interviews, and help you to acquire a dream career in this domain. But before we start with the interview questions, let's take a quick look at Blockchain's demand in the market.
The above figures indicate that Blockchain has a huge demand in the market and you can have a great career as a Blockchain developer. However, there is high competition among Blockchain career aspirants and clearing the interview is no easy task.
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To help you perform best in the Blockchain job interview, we have divided the interview questions into three parts based on the complexity. Let’s start and discuss every topic in detail.
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Blockchain is an incorruptible digital ledger of economic transactions that can be programmed to record not only financial transactions but virtually everything of value.
In simple terms, it is a decentralized distributed database of immutable records that are managed by a cluster of computers but not owned by any single entity. Blockchain is stored as a database or a flat-file.
|Related Article: Blockchain Development Tutorial|
The popular Blockchain platforms are as follows:
|Blockchain Platform||Consensus Algorithm||Ledger type||Governance|
|Proof of Work||Permissionless||Ethereum Developers|
|Hyperledger Sawtooth||Pluggable Framework||Permissioned||Linux Foundation|
|Hyperledger Fabric||Pluggable Framework||Permissioned||Linux Foundation|
|Hyperledger Iroha||Chain-based Byzantine Fault Tolerant||Permissioned||Linux Foundation|
|OpenChain||Partitioned Consensus||Permissioned||Linux Foundation|
|Stellar||Stellar Consensus Protocol||Both public and private||Stellar Development Foundation|
|NEO||Delegated Byzantine Fault Tolerance||Permissioned||On-chain governance through votes of NEO holders and Off-chain governance through NEO Foundation support.|
|EOS||Delegated Proof of Stake||Permissioned||EOSIO Core Arbitration Forum (ECAF)|
|Hedera Hashgraph||Asynchronous Byzantine Fault Tolerance||Permissioned||Hedera Hashgraph Council|
|R3 Corda||Asynchronous Byzantine Fault Tolerance||Permissioned||Hedera Hashgraph Council|
|Quorum||Majority Voting||Permissioned||Ethereum Developers and JP Morgan Chase|
Blockchain consists of immutable records of data called blocks which are linked using cryptography. Cryptography is nothing but a process to encrypt and secure data communication from third parties in reading private messages.
In Blockchain, once the data has been recorded, it will not be changed. Blockchain works like a digital notary with timestamps to avoid tampering with information.
|Related Article: How Does Blockchain Technology Work|
The following reasons will help you understand why blockchain is a trusted approach:
A block in a blockchain is nothing but a digital safe to store the data and lock it forever. The data added on the block is immutable, i.e., data cannot be changed or deleted.
Blocks can be recognized by their block height and block header hash. The data in the block is detected through a computerized algorithm known as a Hash function.
It not only locks the data to be seen by the participants in the Blockchain but also makes the data immutable. Every block has its hash function.
The following are the major elements of a block:
Yes, it is possible. Sometimes, only a particular portion of this online ledger needs to be considered. By using default filters and options, we can remove the blocks.
No, it is not possible to do so. In case any modification is required, the organization has to erase the information from all other blocks too.
Two types of records are available in the Blockchain database. They are:
Both the records can be easily accessed and integrated without following any sophisticated algorithm.
|Related Article: Blockchain Explained|
We can put any records in the blockchain. Some of the common types of records are listed below:
The three major types of blockchains available are listed below:
Public Blockchain: As the name suggests, here no one is in charge, and anyone can read/write/audit the blockchain.
Private Blockchain: As the name suggests, it is the private property of an individual or an organization.
Consortium or Federated Blockchain: Selected members of the Consortium can read/write/audit the blockchain
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A ledger is a file that is growing continuously. It stores the permanent record of all the transactions taking place between the two parties on the blockchain network.
The common types of ledgers considered by the users in the Blockchain are as follows:
In the blockchain, public keys are required for identification and private keys are used for encryption and authentication purposes.
The sender can send a message using the public key of the receiver and the receiver can decrypt the message or the transaction using a private key. By using both keys, communication or transaction is kept safe and tamper-proof.
The major features of Blockchain are listed below:
All the blocks in the blockchain are linked in backward order or each block links with its previous block.
BIP stands for Bitcoin Improvement Proposal.
Encryption is one of the methods of data security that helps organizations keep their data secure. In encryption, any type of data can be converted from a readable format to an encrypted version and can only be decoded by another entity who actually has access to the decrypted key.
In the blockchain, this approach is useful as it adds more to the overall security and authenticity of blocks and keeps them secure.
The primary difference is Blockchain is a digital ledger that can be decentralized very easily and the chances of errors are far less in blockchain ledger when compared with the original ledger.
Blockchain performs all of its tasks automatically, while in the ordinary ledger, every task is completed with hands or human efforts.
A consensus algorithm is a method through which all the peers of the blockchain network reach a standard agreement of the present state of a distributed ledger.
It achieves high reliability and establishes trust between unknown peers in the distributed computing environment.
The most popular consensus algorithms available are listed below:
Different blockchains use different cryptographic algorithms. Bitcoin Blockchain uses a SHA256 Hashing algorithm.
The key benefits of using blockchain technology are as follows:
|Related Article: How to Implement Blockchain|
The below-mentioned ones are the core components of blockchain architecture:
Yes, it’s true that blockchain can never have a parent block. Every block is independent in Blockchain.
Double-spending is considered to be a potential flaw in the digital cash scheme because the same digital tokens are used multiple times. The tokens generally consist of digital files that can be easily cloned.
Bitcoin users protect themselves from double-spending frauds by waiting for confirmations while making payments on the blockchain; the transactions become more irreversible as the confirmations rise.
A blind signature is a form of digital signature in cryptography where the content of the message is blinded before it is signed or considered.
It is mostly used in privacy-related protocols where the author and signing parties are different. It is a verified approach.
Ex: Digital cash scheme
The following are the key principles in a blockchain that help in eliminating security threats:
Proof-of-Work is the original Consensus algorithm in the blockchain. It is used for confirming transactions and producing new blocks to the chain. In this miners compete with each other to complete the transactions on the network and get rewarded.
Proof-of-Stake makes the consensus mechanism completely virtual. In this, a set of nodes decide to stake their cryptocurrencies of the transaction validation.
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A 51% attack or double-spend attack refers to an individual or group of miners on a blockchain who try to control more than 50% of the network’s mining hash rate or computing power.
These attackers try to prevent the new transactions from gaining confirmations and enable them to halt payments between some or all the users.
They are also capable of reversing transactions that are completed while they are in control of the network; it means they could double-spend coins.
A Coinbase transaction is a unique type of bitcoin transaction that is created by miners. It is the first transaction in the new block.
The miners use it to collect the block reward of their work. Any transaction fees collected by the miners are also sent in this transaction.
Merkle tree plays a major role in blockchain technology. It describes a mathematical data structure that is composed of various blocks of data. It also summarizes all the transactions in a block by providing a digital fingerprint of the entire set of transactions.
It allows efficient and secure verification of content across a large body of data. Merkle tree is also known as a Hash tree and mostly used by Ethereum and Bitcoin.
The importance of a Merkle tree in the blockchain is that if anyone wants to verify the specific transaction in a block, they can download the chain of block headers instead of downloading every transaction and every block.
Blockchain, as the name implies, is a chain of digital blocks that stores records of transactions. Every block is connected to all the blocks before and after it.
This makes it difficult for hackers to tamper with the single record as they need to change the entire block containing the record along with the block connected to it for avoiding detection. Blockchain offers an excellent level of security.
In addition to the above, it also offers the following inherent characteristics:
Secret Sharing is one of the primary methods used for providing data security in blockchain.
This approach segregates personal or secret information into various units and sends them to the users on the network. The original information is shared for participants to whom the share of the secret is allocated.
Executive accounting is a special type of accounting that is designed for the business to offer services to the people. In fact, there is no upper limit on the services and the business can manage any through executive accounting.
Blockchain has algorithms that are specially designed for executive accounting, and it cuts down the problems that are associated with the same.
A security policy is a formal and brief plan that embraces the organization's goals, objectives, and procedures for information security.
In simple terms, it defines what exactly needs to be secured from threats and how to handle the situation when they occur.
A trapdoor function is a one-way function, i.e., easy to compute in one direction but hard to compute in the opposite direction unless you have the special information.
These functions are essential for public-key encryption and are most widely used in blockchain development to represent the ideas of addresses and private keys.
Tokens/Coins are used as a medium of exchange between the states. They are digital assets built in to perform a specific function within a blockchain.
When someone does a transaction, there is a change of state, and coins are moved from one address to another address. Apart from that, transactions contain some additional data; this data can be mutated through the change of state.
For this reason, blockchains need coins or tokens to incentivize the participants to join their networks.
In the context of blockchain technology, mining is the process of adding transactions to the large distributed public ledger by providing the proof of work to the network, i.e., generated block is valid.
It also adds new coins to the generated block. The term mining is best known for its association with bitcoin.
Follow the below stages to implement a blockchain project.
On-chain transactions: These transactions are available on the blockchain and are visible to all the nodes on the blockchain network. It includes authentication and validation of a transaction by a defined number of participants.
Off-chain transactions: These transactions deal with the values outside the blockchain and can be carried out using various methods.
Distributed ledger: It is a shared ledger and is not controlled by any central authority. It is decentralized by nature and acts as a database for financial, legal or electronic assets.
Centralized network: A centralized network has a central authority to facilitate its operations.
Decentralized network: The nodes connected in the decentralized network are not dependent on the single server point, and each node holds the entire copy of the network configurations.
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The most frequently used cryptographic algorithms are listed below:
RSA (Rivest-Shamir-Adelman) algorithm is the first algorithm that is used for signing data and encryption. It is most widely used for securing sensitive data.
It is also known as an asymmetric cryptographic algorithm that works on two different keys, namely public and private keys. The public key can be shared with anyone and the private key must be kept secret.
Yes, hackers can attack the RSA algorithm. However, being attacked is not equal to weak protection.
Mostly, there are two ways employed for attacking RSA:
The blockchain has four major elements:
Shared ledger - It is decentralized in nature and is a central component of the blockchain.
Node application - It is software that lets your computer connect with the blockchain. Ex: Bitcoin uses the bitcoin wallet application to detect each mode on the network.
Virtual application - It handles all the tasks that blockchain undertakes.
Consensus algorithm - This is used for managing blockchain rules through which each node can come to a conclusion.
Based on the value of data, there are various approaches employed to handle risk management.
There are no network-specific conditions for employing Blockchain. However, the network must be a peer-to-peer network under specific protocols.
Blockchain approves the new blocks easily and helps organizations to keep up the pace without investing in third-party applications.
If you have any additional questions for us, please mention them in the comment section below and we will get back to you at the earliest.
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Madhuri is a Senior Content Creator at MindMajix. She has written about a range of different topics on various technologies, which include, Splunk, Tensorflow, Selenium, and CEH. She spends most of her time researching on technology, and startups. Connect with her via LinkedIn and Twitter .
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