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Top 20 Blockchain Interview Questions and Answers

Published On: May 25, 2024

Every day, tech enthusiasts and industry experts develop new blockchain-based products. So don’t hesitate to use this collection of top blockchain interview questions and answers to prepare for the sector.

Blockchain Interview Questions and Answers for Freshers

1. What is blockchain technology?

You may program the blockchain to record almost anything of value, including financial transactions. It is an unchangeable digital log of economic transactions.

2. What is Ethereum?

Ethereum is an open-source software platform that allows programmers to create and implement decentralized applications, or programs that are not under the jurisdiction of a single organization, using blockchain technology. You might design a decentralized program in which people make their own decisions.

3. Which blockchain does Ethereum use differently from Bitcoin’s?

The blockchains for Ethereum and Bitcoin are very different from one another, even though both are digital currencies. To function as a digital currency, Bitcoin was developed exclusively. Blockchain technology is more widely used on the Ethereum blockchain. 

Though Ethereum is far more stable than bitcoin, businesses still use distributed ledger technology to develop new services.

4. What is a Blockchain Explorer?

A Blockchain Explorer is a software application that gathers data from a blockchain through an application programming interface (API) and a blockchain node. A database is then used to arrange the data and display it to the user in a searchable manner.

5. What does blockchain hashing mean?

In the blockchain, hashing is converting an input item of any length to an output item of a set length. Consider the usage of blockchain technology in cryptocurrencies, where different-length transactions are subjected to a certain hashing algorithm and result in a fixed-length performance for each.

6. Describe a 51% attack.

A 51 percent attack on a blockchain network occurs when a miner or group of miners tries to take over more than 50% of the hashing capacity, processing power, or hash rate on the network.

In this attack, the attacker may stop new transactions from happening or being validated. When they are in control of the network, they can also undo transactions that have already been confirmed, which could lead to a double-spending issue.

7. What do you mean by blocks in blockchain technology?

A block in the blockchain is just a collection of records. The method of connecting these listings is known as a “blockchain.” For instance, if a business has 100 ledger books, the aggregate is referred to as a blockchain, and a block is the name for each ledger.

8. In the blockchain approach, how is a block identified?

In this online ledger, the main components of each block are transaction data, a time stamp, and a hash pointer that connects to the previous block.

9. Can the data be changed once it has been written in a block?

No, you accomplish it. Should customisation be required, the business only needs to remove the information from every other block. If there is no other reason to use this system, data must be handled very carefully.

10. Do organizations that want to use blockchain technology have any special requirements related to the network?

No, utilizing it is not restricted in any way. Nonetheless, the network needs to be peer-to-peer in order to comply with the concerned standards. It helps companies keep up with the speed in this field without depending on other apps by efficiently validating the new block.

11. How are blocks created on a blockchain?

The blockchain automatically generates new blocks once the block size is achieved. The transactions are kept until the file is finished because the block is a file. The way they are connected means that the most current block is related to the one before it. 

To identify a block, a mathematical procedure is used to create a hash value. It additionally displays any alterations made to a block.

12. What is encryption? What is its role in blockchain?

One method for ensuring the security of the data is encryption. In this method, the sender encrypts the data to some extent before sending it over a network. Only the recipient will be able to decrypt it. This method is helpful in blockchain since it only increases the blocks’ total validity and protection, which strengthens them.

Blockchain Interview Questions and Answers for Experienced

13. Could you please explain what an off-chain transaction is?

An off-chain transaction is a transaction that occurs outside of the blockchain. An off-chain transaction records and validates the transaction using alternative means, whereas an on-chain transaction, sometimes commonly referred to as just “a transaction,” changes the blockchain and depends on it for legality.

14. What are block identifiers?

Every block in a blockchain has a distinct identity. An individual unique identification is generated using the hash value. No two block identities would be the same as a result. Blockchain uses the block height and block header hash to identify blocks.

15. What distinguishes a blockchain ledger from a traditional ledger?

The main difference between a regular ledger and a blockchain ledger is that the former is a distributed database that is easily decentralized. Compared to a typical ledger, this approach has a far reduced mistake rate.

Ordinary ledgers are made by hand or with human labor, but blockchain technology automates every step of the creation process. Now all you need to do is follow the directions to set it up correctly.

16. What is double spending? Can someone spend twice on a blockchain system?

Since digital tokens are usually composed of easily clonable digital files, it happens when a single token is used several times. 

All it does is drive up inflation, forcing businesses to absorb a large loss. Eliminating this practice as much as possible is one of the primary objectives of blockchain technology.

By requiring many parties to validate a transaction before it is posted to the ledger, blockchain prevents double-spending. 

The statement that the entire Bitcoin structure—blockchain, mining, proof of work, complexity, and so on—exists to provide this transaction history that is computationally difficult to alter is not hyperbole.

17. What risks exist for the knowledge you already possess?

Given the current circumstances, knowledge is at great risk. As a result of the increase in online transactions, numerous hackers have entered the fray and are developing novel methods for breaking into databases and servers containing financial information.

Major threats include identity theft, sabotage, data extortion, and software attacks. There are also worms, trojan horses, and other harmful programs.

18. How will you approach risk management in the context of safeguarding transaction record security?

Identifying all risks and weaknesses in an organization’s financial records is the essence of risk management. Using this method, it is best to implement the necessary countermeasures as soon as possible.

Another choice is to have a backup plan in place. Given the value of information, further strategies, including investing in new risk management instruments, might be taken into consideration. The most vulnerable data comes from black-hat hackers.

19. What does a blind signature mean and why is it useful?

A digital signature known as a blind signature is one in which a message’s contents are concealed before they are signed. The generated blind signature can be publicly verified against the original, unblinded message, just like a regular digital signature.

In privacy-related protocols, blind signatures are frequently employed when the signer and message author are not the same person. Digital payment schemes and cryptographic voting systems are two such.

20. Which well-known consensus algorithms are there?

The most widely used consensus methods are:

  • PBFT (Practical Byzantine Fault Tolerance)
  • Proof-of-work
  • Proof-of-stake
  • Delegated proof-of-stake
  • Proof-of-elapsed time


We hope these questions about blockchain interviews will be useful to you in your interviews with blockchain developers. Enroll in our blockchain training in Chennai if you want to learn about blockchain technology and develop a career in the field.

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