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Blockchain Interview Questions You Must Prepare For 2024

Given the growing popularity of Blockchain and the number of new opportunities that are opening in the field every day, it is critical to understand how to prepare for Blockchain interview questions. The most recent industry buzzword is Blockchain, and by 2030, the global value of Blockchain will approach £2.5 trillion, predicts Gartner

Although Bitcoin is excellent, the underlying technology is immense. A revolution is soon to be sparked by something that began as evolution. Due to their understanding of how lucrative this innovative technology would be, investors are making enormous profits. Every day, tech enthusiasts and business professionals create new Blockchain-based products. So, don't wait any longer and use these Blockchain Interview Questions and Answers to get industry ready.

In this Blockchain Interview Questions and answers article, we have compiled the most commonly asked questions by interviewers. These questions were compiled after discussions with leading industry professionals in Blockchain and associated technologies.

This article discusses top frequently asked blockchain interview questions and answers that will help you to get hired by your dream company. Click to learn deeply!

Table of Contents

1) Beginner-Level Blockchain Interview Questions 

2) Intermediate-Level Blockchain Interview Questions 

3) Advanced-Level Blockchain Interview Questions  

4) Conclusion

Beginner-Level Blockchain Interview Questions 

1) What do you understand by Blockchain Technology? How does it work? 

Blockchain is a decentralised, immutable record of economic activity that may be used to record nearly any exchange of value, not just money. 

A Blockchain is a continuously expanding digital ledger that maintains an unalterable, secure record of all transactions that have ever occurred.

Simply described, it is an immutable distributed database that is administered by a group of computers but is not owned by any one organisation. Blockchain data is kept as flat files or databases. Without the need for a third-party middleman like a bank or the government, it may be used for the secure transfer of money, property, contracts, etc. 

2) What are the key features of Blockchain?

The key features of Blockchain Technology are as follows-  

  a) Decentralised Systems 

  b) Distributed ledger 

  c) Faster settlements 

  d) Low transaction fees  

  e) Immutability 

  f) Safe and secure ecosystem 

  g) Minting 

3) State the different types of Blockchains.  

Types of Blockchain Architecture

Public, Private, and Consortium Blockchain are the three different types of Blockchain. 

a) Public Blockchain ledgers are visible to all web users, and any user can authenticate and add a block of transactions to the Blockchain. Bitcoin and Ethereum are two examples

b) Private Blockchain ledgers are visible to internet users, but only certain employees of the company have the ability to validate and add transactions. It is a permissioned Blockchain, meaning that even while the data is accessible to everyone, the organisation itself chooses who gets to control it. Blockstack is an example.

c) In Consortium Blockchain, only specific nodes are in charge of the consensus process. Ledgers, however, are accessible to everyone through the consortium Blockchain. Ripple is an example. 

4) Differentiate between Ethereum Blockchain and Bitcoin Blockchain.




Consensus mechanism

Proof of work

Proof of stake or work


P2P currency

P2P currency and smart contract 

Hashing Algorithm



Time taken to mine a block

10 Minutes (approx.)

12-15 seconds


12.5 BTC


Transaction fee


A fee is calculated in gas


1 BTC = 6934.34 USD

1 ETH = 278.98 USD

5) What do you understand by a block in Blockchain Technology? How is it recognised? 

Every block in this online ledger essentially consists of transaction information, a time stamp, and a hash reference that serves as a connection to the block that comes before it. 

6) Where is a Blockchain stored?

A flat file or a database can be used as a storage platform for Blockchain.

7) What are the two types of records available in the Blockchain Database?

A Blockchain database has two different kinds of records. 

  a) Transactional Records 

  b) Block Records 

The finest aspect is that without using complicated algorithms, it is possible to combine both of these records with one another. 

8) What is a Smart Contract in Blockchain?  

This is an important question in the list of Blockchain Interview Questions.  

Self-executing contracts, known as "smart contracts ", include the terms and conditions of an agreement between peers. 

Some application examples include: 

a) Transportation: Smart contracts make it simple to track the delivery of products. 

b) Protecting copyrighted content: Smart contracts can safeguard ownership rights for things like music or books. 

c) Insurance: False claims can be detected via smart contracts, and they can also be stopped. 

d) Employment contract: Smart contracts can be useful in facilitating wage payments  

9) Where and how do nodes run a smart contract code?

On the Ethereum Virtual Machine (EVM), nodes execute smart contract code. It is a virtual machine created to function as a runtime environment for smart contracts built on Ethereum.

EVM is used in a sandboxed setting (isolated from the main network). This setting is ideal for testing. 

Once your smart contract has been tested and verified, you can deploy it on the main network after downloading the EVM and running it locally in an isolated environment. 

10) How can you identify a block?

Each block contains four fields:  

1) The block's prior hash value (thereby getting linked in a Blockchain) 

2) Details of numerous transaction data are included 

3) The nonce is one of its values. A nonce is a random number that is used to change the hash value in order to get a hash value that is less than the target 

4) Hash of the block itself. It serves as both a block's alphanumeric identification value and digital signature 

The block can only be identified by its hash address. It is a 64-character hex value that contains both letters and digits. The SHA-256 algorithms are used to obtain it. 

11) Discuss the elements of a block in Blockchain. 

These are the vital elements that every block should consist of: 

  a) A hash pointer to the previous block 

  b) Timestamp 

  c) List of transactions 

12) How does Blockchain differ from relational databases?

The difference between Blockchain and Relational Database is shown in the below table:

Point of Difference


Relational Database

 Data unit

Measured in Block 

 Measured as a Table

 Failure occurrence

No chance of occurrence of failure

   Chances of failure can happen

 Centralised Control capability

 Blockchain has the feature of Centralised control

 Relational Database lacks this capability

 Possibility of Data Modification

 Data Modification is not possible in this technology

 Data Modification is possible in Database.              

Existence of single point of Failure

Single point of failure does not exist here

Single point of Failure exists in relational database

13) What is the principle on which blockchain technology is based on?

It makes it possible to share information across users without it being duplicated.


14) What are the benefits of Blockchain Technology?

Blockchain Technology Benefits

Settlement in real-time: Blockchain technology can speed up trade settlement in the financial sector. Due to the availability of a single version of the data that has been mutually agreed upon by all stockholders, verification, settlement, and clearance do not require a drawn-out process. It can be one of the top benefits of blockchain.

Cost-saving: Blockchain eliminates the need for a third party, like a bank, in peer-to-peer transactions, lowering the overhead expenses associated with trading assets. 

Security and Resilience: Blockchain technology employs very sophisticated cryptography to protect the data that will be locked inside it from fraud and hacking attempts.  

Immutability: Since a Blockchain records transactions chronologically, each transaction comes after the one before it. The Blockchain's operations cannot be changed, as proven by the chronological order. It denotes that once a block is included in the network of ledgers, it cannot be altered or withdrawn. 

User Pseudonymity: This is a situation in which a user uses a detectable identification consistently but does not use their real name. Only admins have access to genuine identities. Users are able to converse with others in a largely anonymous manner. 

15) Discuss whether it is possible in Blockchain to remove one or more blocks from the networks. 

Yes, it is possible. Sometimes, only a particular section of this online ledger should be taken into account. This may be accomplished quickly and easily without putting in a lot of work with the use of default choices and filters. 

16) What is cryptography? What is its role in Blockchain?

Blockchain secures users' identities using cryptography and with a hash function, ensures that transactions are secure.

To encrypt and decrypt data, cryptography employs public and private keys. A public key in the Blockchain network can be shared with all Bitcoin users, but a private key (similar to a password) is kept secret from the users.

Blockchain employs SHA-256, which is secure and generates a unique hash output for each input. The basic feature of this algorithm is that it will return a standard alphanumeric output of 64 characters regardless of the input. It is a one-way function that can generate an encrypted value from input but not vice versa.

Learn the fundamentals of Blockchain 101 and Ethereum. Sign up for our Ethereum Developer Training now!  

17) What is a Genesis Block?

1) The genesis block, also known as block ‘zero’, is the first block in the Blockchain.

2) It is the only block in Blockchain that does not refer to the block before it.

3) It determines the parameters of the Blockchain, such as the level of difficulty, consensus process, and so on, in order to mine blocks.

18) What is a Dapp and how is it different from a normal application?

1) A Dapp is a Decentralised Application that is launched utilising smart contracts.

2) A Dapp's back-end code (smart contract) runs on a decentralised peer-to-peer network.

3) Its process consists of the following:

   a) Front-end

   b) The smart contract (backend)

   c) Blockchain (P2P contract)

Normal application:

1) A normal application has back-end code that runs on a centralised server.

2) It is a computer software application that is hosted on a central server.

3) Its process is made up of the following:

   a) Front-end

   b) API

   c) Database

19) What is the very first thing you must specify in a Solidity file?

A version number of Solidity is necessary to be defined at the start of the code as it removes the chances of incompatibility errors that can arise when compiling with another version. This is an essential clause that needs to be at the top of any Solidity code one writes. 

20) What is the nonce and how is it used in mining?

In Blockchain, a process known as mining is used to validate transactions by solving a difficult mathematical puzzle, called Proof of Work (PoW). This process is used to find a number (nonce) along with a cryptographic hash algorithm to produce a hash value lower than a calculated target. To ensure that the final hash value meets the hash conditions, the nonce is a random value used to vary the value of the hash.

21) Why is Blockchain a trusted approach?

A Blockchain is considered to be a trusted approach due to the following reasons:

1) Due to the open-source structure, it is simply compatible with other business applications.

2) Encrypted, safe, and hacking-proof.

3) No central authority is present to control it.

4) How transactions get inserted into the Blockchain, is agreed upon by all Participants.

5) The transaction is immutable i.e., once the transaction is inserted into the Blockchain, one cannot change it.

22) What do you mean by DAO?

The full form of DAO is Decentralised Autonomous Organization. It is a type of organisation that is both decentralised and autonomous. It is represented by rules, encoded as a transparent computer program, commanded by shareholders, and is never influenced by the Central Government. 

A DAO is considered the most complex form of a smart contract. It is a computer program existing autonomously on the internet and simultaneously requires people to perform tasks that it cannot do by itself.

DAO’s record of financial transactions and program rules are maintained on a Blockchain. One can have multiple combinations of old different parties exchanging value and reaching assignment since DAO runs on a Blockchain and further it also runs on a distributed network. That implies, to a Decentralised Autonomous Organisation, it doesn’t matter whether one is a human being or a robot.

One can have either device communicating with people or a device communicating with devices or people communicating with people. It makes no difference to a DAO because as long as it is programmed into the smart contracts collection, the whole thing runs automatically and is immutable.

23) What do you mean by Coinbase transaction?

The first transaction in a block is called as a Coinbase transaction. It is known to be a unique type of bitcoin transaction that is created by a miner. For their work, they use this transaction to collect the block reward, and in addition, any other type of transaction fees collected by the miner is also sent into this transaction.

Learn how bitcoins work and how to secure bitcoins. Register for our Bitcoin and Cryptocurrency Course now! 

Intermediate-Level Blockchain Interview Questions 

1) List some popular platforms for developing Blockchain applications 

Some of the most popular platforms for developing Blockchain applications are: 

  a) Ethereum 

  b) Hyperledger Sawtooth 

  c) Quorum 

  d) Ripple 

  e) R3 Corda 

  f) Qtum 

  g) IOTA 

  h) EOS

2) Can you modify the data in a block? 

You cannot change the data within a block. You must also remove the data from any other related blocks if any update is necessary. 

3) What do you understand about the security of a block? 

Well, a block or the whole Blockchain is secured by a strong cryptographic hash algorithm. Every block has a different hash pointer. The block's hash identification will change whenever any of the block's components are altered. As a result, it provides a prominent level of security. The safety and security of the data contained in a block are, thus, not a concern. 

4) What is the Merkle Tree? How is it important for Blockchains? 

A block is verified using a data structure called a Merkel Tree. It has the shape of a binary tree and contains the block's individual cryptographic hashes. The leaf node of a Merkle tree is a hash of a block of transactional data, and each non-leaf node is a hash of its leaf node. This system is similar to that of a binary tree. The resulting hash root of all transaction hashes is known as the Merkel root. It includes all the transactions supporting every non-leaf node.

Merkle Tree

An essential component of Blockchain technology is the Merkle tree. There is no need to download the full block to verify a single transaction in a block if someone only needs to confirm its presence. It is limited to downloading the block header chain. It enables downloading a collection of the transaction's branch from the tree, which is sufficient. The hashes that are pertinent to your transactions are checked. 

5) What is a ledger? List the different types of ledgers in Blockchain. 

A ledger is a continuously expanding file. All the exchanges between two parties on the Blockchain network are permanently recorded by it. 

Users of the Blockchain can take into account one of three popular types of ledgers: 

1) Centralised Network 

2) Decentralised Network 

3) Distributed Network 

6) Which cryptographic algorithm is used in Blockchain?

SHA-256 Hashing Algorithm is used by Blockchain. This algorithm was developed by the National Security Analysis (NSA) in the USA.

7) In what order are the blocks linked in the blockchain?

Each block is linked in backward order in the Blockchain. It means each block is linked with its previous block.

8) What is Double Spending? Is it possible to double spend in a Blockchain system?

Double spending implies spending the same money more than twice. The double-spending problem can never arise in a physical currency, whereas in digital money like Bitcoin, this problem can arise. Therefore, in Bitcoin transactions, there remains a possibility of copying and rebroadcasting, resulting in the possibility that the same bitcoin could be spent twice or more by its owner. Blockchain technology’s primary aim is to eliminate the approach up to the greatest possible extent.

9) Blockchain vs Hyperledger - what's the difference? 

Blockchain is a decentralised system made up of immutable records, or blocks, that are encrypted and safeguarded. A platform or organisation called Hyperledger enables the creation of private Blockchains.  

While Hyperledger only allows for the creation of private Blockchains, Blockchain allows for the creation of both public and private Blockchains. 

Hyperledger is a private Blockchain technology with access to Blockchain data and is restricted to predetermined users, configurations, and programming. Blockchain is separated into public, private, and consortium Blockchains. 

While Hyperledger is largely utilised for enterprise-based solutions, Blockchain can be used in a variety of sectors, including business, government, healthcare, etc. Public Blockchain refers to the use of Blockchain over the internet in all contexts, while Hyperledger-based Blockchain solutions are designed for intranet use within an organisation. 

10) Is Blockchain different from Banking Ledgers?  

Blockchain is thought to be incorruptible. Not to forget the energy needed to power the computers required for the Blockchain system to function; should that occur, the person would take all reasonable measures to avoid being recognised. 

11) How are Blockchain Distributed Ledgers different from Traditional Ledgers?


Distributed Ledger 

Traditional Ledger 


Only Insert Operations 

Performs C.R.U.D.  


Replication of every block on each peer 

Multi Master and Master- Slave   


Most of the peers agree on the outcome of transactions 

 Distributed Transactions 
(2-phase commit) 


Anybody can validate transactions across the network 

 Integrity Constraints

12) Do you know the difference between Blockchain and Database?



Blockchain is Decentralised. Because there is no administration present, everyone is in charge.

It has a centralised database. All of the data is within the authority of administrators.

Reading and writing are rights for everyone.

Only those with permission are able to read and write.

Peer-to-peer technology.

Server-client architecture

Only the append operation is permitted here.

It is possible to use a CRUD (Create, Read, Update, Delete) mechanism.

Digital records with historical information.

No ownership records exist.

Blockchains are completely private

Databases are not completely private.

Blockchain is inefficient since it is reliant on hash rate.

Because there are fewer individuals managing the database, it is quick.

Blockchain is an open network.

The database is password-protected.

13) What do you understand by Cryptography, and what is its role in Blockchain? 

With the use of a hash function, Blockchain enables cryptography to protect users' identities and ensure that transactions are completed securely. 

Data is encrypted and decrypted using public and private keys in cryptography. A private key (just like a password) is kept secret from other users on the Blockchain network, whereas a public key can be shared with all Bitcoin users. 

Blockchain makes use of the secure SHA-256 algorithm, which produces a distinct hash value for each input. This algorithm's fundamental property is that it will output 64 characters of conventional alphanumeric data regardless of the input you provide. It is a one-way function; the input can be used to generate an encrypted value, but not the other way around. 

14) Name some of the universally used Cryptographic algorithms in Blockchain.  

Below are a few universally used Cryptographic algorithms in Blockchain: 

  a) SHA - 256 

  b) RSA (Rivest-Shamir-Adleman) 

  c) Triple DES 

  d) Ethash 

  e) Blowfish

15) Explain what happens when you try to deploy a file with multiple contracts. 

In Blockchain, deploying a file with multiple contracts is not possible. The compiler only deploys the last contract from the uploaded file, and the remaining contracts are neglected. 

16) Tell me more about the RSA algorithm? How secure is this algorithm?

RSA Algorithm

1) RSA in Cryptography stands for Rivest, Shamir, and Adleman, who are credited with explaining it as an algorithm that can be used for public-key cryptography.

2) It also became the first algorithm which is suitable for signing, and encryption.

3) This algorithm involves a public key and a private key.

Security of RSA Algorithm

1) Brute Force: All possible secret keys are used to gain access to a system.

2) Mathematical Attacks: In a Mathematical attack, one uses different techniques, similar in effort to factor the product of two primes.

17) How will you handle the risk management when it comes to securing the transaction records?

Risk Management is the process of locating all the threats and vulnerabilities to the financial records of an organisation. With this approach, one best thing that can be done is taking the right countermeasures against them immediately.

A second approach is to pay attention to a backup plan. Based on the value of information, other approaches like buying new risk management software can be simply considered. The main risk to information is from the black-hat hackers.

18) What are the core requirements for a Business Blockchain?

The core requirements of a Business Blockchain includes, a shared ledger, smart contract functionality, trust and privacy.

19) What is a security policy?

A security policy is defined by what exactly needs to be secured on a system. Under some core protocols, network users are bound that they must agree and follow so that the overall security is enhanced. Multiple security policies are employed if it comes to information or financial records of an organisation.    

Learn to create and deploy your Private Blockchain on Multichain. Check out our Blockchain Training Course today! 

Advanced-Level Blockchain Interview Questions 

1) What is a Blind Signature? Explain its significance. 

In this type of digital signature, the message's content is hidden (blinded) before it is signed. Similar to a standard digital signature, the resulting blind signature can be publicly validated against the original, unblinded message. 

In privacy-related procedures, blind signatures are frequently used when the message author and the signer are two different parties. Digital payment schemes and encrypted voting systems are two examples. 

2) What are the steps involved in the Blockchain Project Implementation? 

This process involves 6 steps, which are: 

1) Requirement identification 

2) Screen ideas consideration 

3) Project development for Blockchain 

4) Feasible study on the security 

5) Implementation 

6) Controlling and monitoring the project 

3) What is Secret Sharing? How does it benefit Blockchain Technology? 

The importance of security in digital transactions is well-known. A strategy for the same is secret sharing. It is a method in Blockchain technology that separates confidential or confidential information into smaller components and transmits them to network users. 

Blockchain technology has a number of advantages in terms of security. The original data can only be joined when a person who has been given a share of the secret chooses to do so.

4) What is meant by Executive Accounting, and does Blockchain support it?  

Executive accounting is a unique type created for businesses to provide services to the general public. In actuality, there are no limitations on the services, and they can be managed by the company through executive accounting.

Executive accounting concerns are reduced by Blockchain's use of algorithms that are specifically created for this purpose. 

5) Differentiate between Centralised Network, Decentralised Network and Distributed Ledger.  

  1) Distributed ledger: It is a shared ledger that is not under the control of a single entity. It functions as a database for financial, legal, or electronic assets and is decentralised by nature.  

  2) Centralised network: A network with centralised authority can operate more efficiently.  

  3) Decentralised network: Each node in a decentralised network has a complete copy of the network configurations and is not reliant on a single server point. 

6) What are the important elements of the Blockchain Ecosystem?  

Elements of Blockchain Ecosystem

The Blockchain has four major elements: 

a) Shared ledger - It's a key element of the Blockchain and is decentralised in nature. 

b) 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. 

c) Virtual application - It handles all the tasks that Blockchain undertakes. 

d) Consensus algorithm - This is used to control the Blockchain's rules, which determine how each node can conclude. 

7) What Is Hashing in Blockchain?

Hashing in Blockchain is the process of making an input item of any length so as to represent the output item of a fixed length. For instance, the usage of Blockchain in Cryptocurrencies, where different length of transactions is run through a given hashing algorithm, and all of them produce a fixed length performance.

8) What are some of the popular Cryptocurrencies?

Some of the well-known Cryptocurrencies are:

a) Bitcoin (BTC)

b) Ethereum (ETH)

c) Ripple (XRP)

d) Litecoin (LTC)

e) Bitcoin Cash (BCH)

9) What are Blockchain Durability and robustness?

In the year 2008, Bitcoin was established. Since then, there has been no damage done to the Bitcoin network. For close to 30 years, the internet proved to be a trustworthy resource. It’s a track record that shows a bright future of Blockchain technology.

10) Name some of the popular consensus algorithms?

Some of the well-known Consensus Algorithm includes:

a) Practical Byzantine Fault Tolerance (PBFT)

b) Proof-of-work (POW)

c) Proof-of-stake (POS)

d) Delegated proof-of-stake

e) Proof of elapsed time

11) Explain the difference between Proof of Work and Proof of Stake? 

Proof of Work (PoW): 

In Blockchain, PoW is the method used to solve a complicated mathematical puzzle called mining. The amount of computation a miner performs determines the likelihood of mining a block in this case. The cryptographic puzzle requires a lot of processing power, which miners invest in hardware to solve. 

Proof of Stake (PoS): 

PoS is a PoW substitute in which Blockchain tries to achieve distributed consensus. The quantity of tokens you possess determines your likelihood of validating a block. The more opportunities you have to validate a block, the more tokens you possess. It was developed as a way to reduce the consumption of costly resources used in mining. 

12) Describe a real-life use case of Blockchain Technology.  

Smart contracts in supply chain management offer ongoing validation and transparency of transactions handled by numerous supply chain parties. 

13) Explain the various parts of EVM Memory. 

An EVM has three distinct types of memory:  

1) Storage

  a) The Blockchain network permanently retains storage values. 

  b) It is incredibly costly. 

2) Memory

  a) Memory is a transitory, customisable storage. 

  b) It is only accessible when a contract is being executed. Upon completion of the execution, its data is lost. 

3) Stack

  a) A stack serves as transient, immutable storage. 

  b) In this case, the content is lost when the execution is finished. 

14) What does BIP stand for?

The full form of BIP is Bitcoin Improvement Proposal.

15) What is a trapdoor function in blockchain development?

A trapdoor function is a type of function that is unidirectional i.e., it is easier to compute in one direction but difficult to compute in the opposite direction unless one has a piece of special information. For public-key encryption, these functions are essential and are widely used in Blockchain Development to represent the ideas of addresses and private keys.

16) Why does Blockchain need coins or tokens?

A Blockchain needs tokens or coins because they are used as a medium of exchange between the states. Within a Blockchain, these are digital assets built to perform a particular function. For instance, when a transaction is carried out by someone, there is a change of state, and coins are moved from one address to another one. In addition, transactions carry some additional data, which can be mutated through the change of state.

Because of this reason, to incentivise the participants to join their network, Blockchains need tokens or coins.

17) What is the difference between a scriptPubKey and a P2SH address?

A scriptPubKey, also termed a locking script, is found in transaction output. Whereas, a P2SH address is a special kind of address, i.e., its usage is for replacing complex locking script with the hash. Apart from the unlocking scripts, the transaction necessarily contains the scripts that matches the hash.

18) What is Mining?

Mining, in reference to Blockchain Technology, is defined as the process of addition of transactions to the large distributed public ledger by giving the proof of work to the network, i.e., validating the generated block. Mining also adds new coins to the generated block. Mining as a term is best known for its association with bitcoin.

19) What do you understand by a 51% attack? 

A miner or group of miners seeking to control more than 50% of a network's mining power, computational power, or hash rate is known as a "51 per cent attack" on a Blockchain network. The attacker of this attack has the ability to prevent the confirmation or execution of additional transactions. Moreover, they can undo transactions that have already been confirmed when they were in charge of the network, which creates a problem with double-spending. 

20) Name organisations that use Blockchain Technology. 

The type of business that can take this method has no clear upper limit. The reality is that practically all organisations engage in online or financial transactions in order to keep their operations running properly. This system is extremely simple to trust by large firms, financial institutions, private businesses, government agencies, and even defence organisations. 

21) Differentiate between off-chain transactions and on-chain transactions? 

On-chain transactions: 

All nodes on the Blockchain network can see these transactions because they are available on the Blockchain. It involves a predetermined number of parties authenticating and validating a transaction. 

Off-chain transactions:

These transactions, which can be executed in a variety of ways, deal with values outside the Blockchain. 

22) What is a Public Key?

A Public Key is made consists of line of alphanumeric characters. These are specifically related to a particular address or node. In a Blockchain, a Cryptographic algorithm facilitates peers to obtain funds in their blockchain wallet using a Public Key.

When a public key connects with a private key are connected, pair of keys are created. The usage of private-public key pair is to ensure that the Blockchain’s security is maintained. 

23) What is a Private Key?

A private key, consisting of an alphanumeric term is used to encrypt and decrypt data associated with a public key. A private key is also a component of the cryptographic algorithms in  Blockchain security.

The key is allocated to the key generator and can only be used by the user. If the user fails, somebody else can gain access to the wallet’s information as well as the address for which the private key is stored. 

24) What is Transparent and incorruptible in blockchain?

Once in, every 10 minutes, a Blockchain network checks itself to ensure that is in state of consensus. The network functions as a digital value’s self-auditing ecosystem that conforms to any transaction that occurs in ten-minute intervals. A “block” is a collection to these transactions.

Transparency data as a definition is available as it is embedded in the network as a whole. It is not easy to tamper because a change in every single unit of data will require an extensive amount of computational power to evade the entire network.

25) What Do You Think About the Future of Blockchain?

The future of Blockchain is very bright. Right now, it is in its developmental phase with both technical and adoption advancements. The application of Blockchain in every industry speaks volumes about its future.

As more and more investors show an interest in Blockchain Technology, a huge effect on the Blockchain will be seen, both industrially and in daily life. Some other technologies like AI, and Bigdata can also be used in conjunction to make it more practical and effective.

26) What are function modifiers in Solidity? Name the most extensively used modifiers.

Utilising function modifiers in Solidity, you can quickly change how your smart contract functions behave. Basically, it can offer new functionality or impose constraints on how well smart contracts work. The following are the most frequently used function modifiers in Solidity:  

a) View, which are operations that have no influence over a smart contract's state and have read-only capabilities.  

b) Pure, are operations that do not read or write a smart contract's state. They both provide the same outcome based on their input values.

Blockchain Training

27) What is the Fork? Explain its types. 

The phrase "forking" refers to the process of altering a cryptocurrency system or code. A fork indicates that a Blockchain separates into two branches. It may take place if the networks' users are unable to agree on the consensus method and new guidelines for transaction validation. 

Three different forking types are: 

1) Hard forks 

2) Soft forks 

3) Accidental forks 

28) What happens if the execution of a smart contract costs more than the specified gas? 

Your transaction will initially be carried out, but if the cost of carrying out a smart contract exceeds the allotted gas, the miners will stop verifying your contract. The transaction will be marked as unsuccessful on the Blockchain, and the user will not receive a refund. 

29) What is Cryptocurrency?

Cryptocurrency is defined as a digital asset (currency) that can be used to exchange value between parties. It uses strong cryptography to verify and secure financial transactions and also control the creation of new units of that currency. Since it is a digital currency, it doesn’t exist physically. Examples of popular cryptocurrencies include Bitcoin, Litecoin, Z-Cash, Monero, Dash, etc.

It is well known that government prints fiat currencies like Dollars, Euros, or Rupees. That implies, there is a centralised institution that can create thousands or millions more of that currency. Bitcoin, unlike the fiat currencies, is created by the same mathematical formulae which make cryptography work.

Therefore, cryptocurrencies use decentralised control, that works through distributed ledger technology which serves as a public financial transaction database.

30) What are the limitations of blockchain?

The major shortcomings of Blockchain include the following:

1) Shortage of Technical Talent: In every field today, there are a lot of available developers who can possibly do a lot of different things. But in the field of Blockchain Technology, there are not many available developers who are experts in this technology. Hence, a shortage of technical talent is a hindrance to the development of Blockchain. 

2) Size of Network: A vast network of users is considered a necessity in Blockchain networks. Hence, to the wrong actions, it is not that effectively resistant as well as it responds to attacks and grows stronger. With a widely distributed grid of nodes, the Blockchain is a robust network making it difficult to reap the benefits.

3) Consensus Mechanism: In a Blockchain, a block gets created every ten minutes because every transaction made should necessarily ensure that each block in the Blockchain network must reach a common consensus. Due to dependency on the size of the network and the number of blocks or nodes involved in the Blockchain, the back-and-forth communications involved in attaining a consensus can take a substantial amount of time and resources.

4) Transaction speed and costs: Transaction costs were nearly free during the first few years of the existence of the Blockchain. But as the network gets bigger, it will not be the most effective option for money transfer due to the rising cost of transactions. By the end of 2016, it processed seven transactions per second with each transaction costing around £0.17.

5) Flaw in Security: A security flaw known as 51% attack is associated with Bitcoin and other Blockchains. This flaw occurs when a group of miners takes control of more than half of the computing power of the Blockchain Network. There is no centralised authority to prevent it from influencing the entire Bitcoin network, once the miners acquire a sufficient amount of computational power. It also implies that the attacker can block new transactions which are being confirmed or are taking place. They can also reverse the transactions, that have been already validated during that same period. It is due to this reason; Bitcoin mining pools are monitored closely by the community who ensure nobody gains such network influence.

31) What is encryption? What is its role in Blockchain?

Encryption is defined as the process of converting data or information into a code to prevent unauthorised access. It helps organisations to secure their data. In this technique, data or information is encoded or changed into an unreadable format to some extent before it is sent out of a network by the sender. The only thing that a receiver can understand is how to decode the same.

This approach is very useful in Blockchain Technology as it makes the overall security and authenticity of blocks and help to keep them secure.

32) How does the security of a block works?

A chain of blocks in a Blockchain contains a record of transactions. A block is considered to be the most secure part of a Blockchain. Through a cryptographic hash algorithm, the record of a blockchain is protected. The connection of each block with all other blocks before and after it is done through a distinctive hash pointer which also adds security to the block.

This hash is basically a security identifier that provides a reasonable level of security to the whole Blockchain. If within a block the value is modified, there will be a change in the hash value.

To make changes to the block information, hackers also need to know the hash key of the previous block. For such hackers, Blockchains are decentralised across peer-to-peer networks that get continuously updated and keep syncing. These records are not contained in a centralised location, hence Blockchain don’t have a single point of failure and also can't be changed from a single computer.

33) What is the difference between public and private key?

A private key is used to lock or encrypt a message sent on a Blockchain Network. Using the public key of the receiver, a sender can send a message. On the other hand, using a private key, a receiver can decrypt the message or the transaction. By using the public and private keys, any communication or transaction is kept tamper-proof and safe.  

34) How does bitcoin use Blockchain?

A transaction happens when there is a value transfer between Bitcoin wallets that gets included in the Blockchain. A secret piece of data known as a private key is kept by Bitcoin wallets. The usage of this private key is to sign transactions and provide mathematical proof that have come from the owner of the wallet.

35) What is Consensus algorithm?

The method of achieving consensus on a change of data over the system or distributed network is termed a Consensus Algorithm. This algorithm is extensively used in Blockchains as they permit the network of unknown nodes so that it reaches a consensus on the data that is being shared or stored through the blockchain.

36) What are the types of consensus algorithms?

There are different types of consensus algorithms widely known, out of which the popular ones are listed below:

a) Proof-of-Work (PoW)

b) Proof-of-Stake (PoS)

c) Delegated Proof-of-Stake (DPoS)

d) Proof-of-Authority (PoA)

e) Proof-of-Elapsed Time (PoET)

f) Byzantine Fault Tolerance


Hope these Interview Questions on Blockchain will help you to sail through your Blockchain developer Interviews with confidence. However, if you want to dive deep, wish to advance a career in the field of Blockchain, and gain expertise in Blockchain Technology, check out our Blockchain Training Courses today! 

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