Top 30 Blockchain Interview Questions and Answers

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“Choose a job you love, and you will never have to work a day in your life.” 

Author unknown

How true is that? A job that does not carry its essence !!! A wishful thought, yet powerful.

Without a doubt, all readers here must be a techie, devoted to the computer and digital world. Your passion for computing has driven you to research blockchain course technology. Readers could be here for various reasons. Either your interviewer has selected you, or you plan to pursue a career in this domain. This guide will be a refuge for many knowledge seekers.

Why Should you Read this Post?

• This guide will help calm your nerves by answering many probable interview questions.
• Although there may not be a right or wrong answer yet there is ALWAYS a specific answer that the interviewer seeks!
• Many experts from the field of the Blockchain industry have answered in detail.

True, I will address the top 30 blockchain interview questions and answers but first, let us understand the concept of Blockchain in simple terms.

Blockchain is a digital structure that records information. These are blocks that hold all the transactions in a disseminated form. Here nobody can cheat or hack as it ensures complete security and transparency. Above all, the information stored is not on a single computer. It distributes data across the network and protects from theft. 

This system is a chain that stores data for everything. Blockchain records transactions relating to financial or even medical data. It is the underlying technology of the cryptocurrency revolution.

I have explained the Blockchain system in simple terms, so now we will delve into the interview. The questions are divided into 3 sub-sections.

• General questions
• Multiple-answer Questions
• Advanced Questions

Here the interviewer is seeking a concise yet impactful answer. Use self-explanatory power words. Do not unleash your knowledge right away. Hold on to your reins and go steady.

Happy reading!!!

Q1. What do you understand about the blockchain system? How do you distinguish Bitcoin Blockchain from Ethereum Blockchain?

Answer A Blockchain is a decentralized database system. Its data is irreversible and thus establishes security. Bitcoins are the first crypto-currency; they run on Blockchain technology.

Bitcoin uses digital currency while Ethereum Blockchain uses Smart Contracts. 

Blockchain sounds complicated yet its technology is quite simple. It is a structured collection of information or a type of database. These blocks contain data that chain together. New blocks accept new data as the old ones get full. Each block attaches to the previous one in chronological order and creates a reference point. This information becomes immutable and therefore protects all records. It allows for transparency in the transactional ledger.

• The Crypto-Currencies used are Bitcoin and Ether respectively. 
• The algorithm used by Bitcoin is SHA-256 when Ethereum uses Ethash. 
• Although the block time taken by Bitcoin is 10 minutes, Ethereum takes about 12-14 seconds.

Q2. Do you say that a Blockchain is the same as a database?

Answer The data structure is the main difference between Blockchain and the database. A database assembles the information into tables, unlike a Blockchain which groups information into blocks.

No, the storage structure has a different model in both systems. In a Blockchain, the data gets converted into blocks and fastens together to form a chain. When a block fills, it obtains a timestamp and a permanent place in the timeline.

The typical database stores its data as tables where only the appointed individual can access it.

Q3. Are you referring to the decentralization aspect of Blockchain technology? Please explain.

Answer : Decentralization is one of the fundamental features of Blockchain. This system comprises thousands of computers housed at various locations enabling separate entities to operate independently. Each computer in this network is called a node. These nodes record every transaction on the Blockchain.

Yes, decentralization is a primary feature of this technology. Each node connects with the entire network of computers for cross-reference. Hence all nodes facilitate correction by referencing the other nodes. The ability to trace and rectify all errors establishes a well-constructed order of all accounts.

This transparency allows individuals and groups to access the transaction from across regions.

Q4. Is this technology a trusted approach? Why?

Answer : Yes, Blockchain is a trusted and stable approach and has no incompatibility issue with other applications. All the transactions are immutable.  

Yes, there are many reasons to trust Blockchain. It assures security to all transactions. Nobody can hack or cheat you as all events are traceable.

Every business can implement this structure to store data as all information recorded becomes immutable.

Q5. What are the key features of Blockchain?

Answer: Name the prominent properties of this approach.

The central characteristics of Blockchain are:

• Decentralized operations
• Low transactional cost
• Safe and secure network
• Minting

Q6. Explain the different kinds of Blockchain.

Answer: A public Blockchain is a permissionless Blockchain. There is no governing body; everyone is free to read, write and audit. It is an open-source public ledger where anyone can review the Blockchain.

A single authority controls a private Blockchain. Only the approved community has the discretionary power to determine who can access its transactions. Thus it is an approved blockchain.

A consortium Blockchain is where an elected body of members acts as the custodians. They are the decision-makers who influence the whole network.

A semi-private application is where a single authority controls the system but gives access to any candidate who qualifies.

Q7. Which Blockchain application segment do you think will become the hot flavor?

Answer: There is a generic difference between a public and a private application segment.

The difference lies in the following :

• Public segments are cheaper to use when private ones are expensive. 
• Public segments are more generic. In contrast, private sections are more specific because a designated group holds the credentials.

I believe the semi-private sector is going to take it by storm. Possibly, companies would start giving access to customers to check the status or update.

Q8. What are the platforms where you can develop Blockchain applications?

Answer: Platforms help build the framework of the blockchain wherein people can host and develop the application.

The 8 most important platforms are:

• Ethereum
• Hyperledger Sawtooth
• Quorum
• Ripple
• R3 Corda
• Qtum
• IOTA
• EOS

Q9. How do you recognize a block in the Blockchain approach?

Answer: Each block has a hash value. This hash value is a link to the previous block and the transaction data. Every block contains a timestamp.

Q10. Can we change the data on a block?

Answer: No, we cannot change data because blockchain is immutable. If alterations are inevitable, then the authorised body has to delete data from all other blocks. For this reason, recording data on this system requires the utmost care.

Q11. In such a case, would it be possible to remove a few blocks from the chain?

Answer:  Sometimes only a part of the ledger has to be modified. We have to operate using the default options and filters to enable removal.

Q12. What do you understand about block security?

Answer: Each new block uses a cryptographic chain to connect to the previous block, creating a cryptographic algorithm. The system assigns a hash value to every block. In the event of any modification, the change will reflect in the hash value. This consensus mechanism makes it tamper-proof.

Q13. That leads us to Merkle trees. What are they and how do they benefit us?

Answer: Merkle tree, also known as the hash tree is a data structure composed of different hashes. It is vital for the efficient validation of content in an extensive database. 

This data tree has a leaf node containing the cryptographic hash of a block, while the non-leaf nodes comprise the cryptographic hash of the child nodes. 

This structure verifies information both accurately and efficiently.

Q14. Name the type of ledgers used in Blockchain.

Answer:  The ledgers are:

• Centralised ledger
• Decentralised ledger
• Distributed ledger

Q15. Name the activities and transactions recorded in the blockchain.

Answer :There are no restrictions in recording transactions. The following are the common records held by organisations:

• Medical transactions
• Documentation
• Organizational events
• Management events
• Transaction processing

Q16. Which cryptographic algorithm does it use?

Answer :It uses the SHA-256 hashing algorithm. NSA in the US develops this hashing algorithm.

Q17. Explain the benefits of Blockchain technology.

Answer : The following are the benefits:

Better transparency

Organizations implement centralization to improve transparency, but this move has adversely affected the industry. Because of centralization, companies accommodated more rules and formed a stringent process of recording transactions. This affected negatively and they introduced the consensus method where peers execute and validate transactions. This centralised authority improves transparency.

Enhanced security

Every transaction has to go through the consensus method, which validates and records. Transaction encryption creates links to form the blockchain to create reference points. 

Since each node has recorded transactions from the inception, it is impossible for the discrepancy to creep in.

Reduced costs

The application of blockchain technology eliminates all 3rd party vendors as there is no centralization of authority.

Traceability

The supply chain operations of an organization benefit tremendously when they implement in-house blockchain technology. A company can create a focussed systematic arrangement between the suppliers and vendors. By observing this, it enables the supply chain to process smoothly and helps end all malpractice.

Improved speed and efficiency

The power of automation eradicates all human error and minimizes time. Blockchain streamlines digital ledger and maximizes efficiency.

Q18. What are the components of the blockchain ecosystem?

Answer: The components are:

Node Application

Every node must install a computer application modelled according to the particular ecosystem.

Shared Ledger

Each node application manages a data structure, the ledger. If you use the Ethereum client, then you can see the Ethereum ecosystem ledger, and if you run the Bitcoin client, then you see the bitcoin ecosystem ledger.

Consensus Algorithm

This consensus algorithm is a part of the node application and it provides the standard guidelines for the Ecosystem to bring a single-view ledger. Each Ecosystem has unique features so they carry different protocols to reach a consensus.

Virtual Machine

The virtual machine is a part of the node application and it operates with instructions in its personal ecosystem.

Q19. What is double-spending? Does the Blockchain system control it?

Answer: Spending digital currency twice is an underlying problem potential to all digital currencies. Duplication of digital information is an effortless task for a tech enthusiast who has the knowledge to manipulate the Blockchain System. There runs a risk of transferring the clone of the digital currency and holding back the original.

Although Bitcoin, a cryptocurrency, runs under the decentralized transactional mode, Blockchain ensures protection. Blockchain has a mechanism that averts double-counting by verifying each transaction.

Multiple-choice Questions:

Q20. Bitcoin uses ________________ Blockchain

1. Public 
2. Private
3. Permissioned
4. Public permissioned

      Answer

      Public.

Q21.Blockchain can be stored as_________________.

1. A flat file
2. A Database
3. Both are correct
4. Both are wrong

Answer

Both a flat file and a database.

Q22.The benefit of immutability is_______________.

1. Scalable
2. Better security
3. Improved efficiency
4. Tamper proof

Answer

Improved efficiency

23. Blockchain forks result in____________

1. Multiple parent blocks
2. Multiple children blocks

Answer

Multiple children blocks

Q24. Name the asymmetric encryption algorithm.

1.  Triple DEA
2. Blowfish
3. RSA
4. Twofish

Answer

RSA

Q25. What do you know about the RSA algorithm? Tell me about it.

Answer: Modern computers use the RSA (Rivest-Shamir-Adleman) algorithm to encrypt and decrypt messages. This algorithm is asymmetric cryptographic, which means it uses both the public key and the private key. While a private key remains discrete, the public key is for a public view as the name suggests.

 

This algorithm is distinct as it has a mathematical property that uses the private key to decrypt any public key. This feature enables communicating where the RSA user did not receive the keys earlier. 

 

So in simple terms, if you are communicating with an RSA user and you encode the message using a public key, the other RSA user has to use his private key to view the message. Each RSA user has a key pair of both the private and the public keys.

Q26. What is a blind signature and how is it useful?

Answer : Blind signature is a digital signature applied in privacy-related protocols.

They base the blind signature protocol on the RSA algorithm. The core tenet of this scheme is to make the agent sign the message without disclosing the message. Cryptography approves this form of digital signature by disguising the message before divulging the content. We can later validate blind signatures against the original message.

This mechanism helped develop digital cash schemes and eVoting along with other privacy crypto protocols like anonymous credentials.

Q27. What is secret sharing? Can you explain?

Answer : Another name for secret sharing is secret splitting; This refers to the splitting of a message and allotting to multiple people without revealing the message.

Since security is important in the world of digital transactions, we utilise this approach to secure encryption keys. This is a scheme to secure a secret in a distributed way.

This system allows you to split a secret into shares and assign them to many participants by keeping the secret intact throughout. The original message divulges when participants consensually agree to combine all of their shares with the others.

Q28. What are off-chain transactions?

Answer Off-chain transactions are blockchain transactions wherein the agreement occurs outside the Blockchain. The parties to this transaction can deal outside the blockchain system with a third party overseeing the completion of the contract. The third-party acts as a guarantor by certifying that the agreement complies with the guidelines.

 

Many decentralized exchanges adopted this model where the exchange plays the part of the escrow. The real transaction commences on the blockchain once the agreement settles “off-chain” between the contractual parties.

Q29. Are there any threats to the information stored?

Answer We see online transactions escalate sky-high due to which hacking and tampering with online financial information also amplify to the next level. Active hackers are manipulating data and adopting new ways to extract them.

Other threats are identity theft, information extortion; viruses and trojan horses to name a few.

Q30. How can we manage the risk while securing the transactional records?

Answer We must study the risks and threats involved while setting up a financial information database structure. After the observation, we must counteract the potential threat by taking appropriate measures like installing risk management software.

If we approach with a backup plan then we can offset many threats including attacks from back-hat hackers.

So these were the most important Blockchain interview questions that some of our experts have answered. I hope I have done justice for this vast topic.

Conclusion

Blockchain and its revolution are sweeping across industries. Introducing this technology has transformed many processes and is radically strengthening many businesses. It began with digital currencies but now has sprung across different industries to leave an indelible mark.

 

Content distribution is one such industry where this system has influenced. By decentralising content distribution, this technology has promoted the work of content creators over distributors. The creators can earn cryptocurrencies by sharing their content online now.

 

The real estate industry has also paved the way for this giant to take over the networking platform.

Thus, by incorporating blockchain, buyers and sellers can interact with each other by eliminating the intermediaries.

 

This article about the blockchain revolution reveals how this economy will permanently change and this technology will continue to evolve and impact more lives.

Readers who are interested in starting a career in this field can visit

 

Henry Harvin Blockchain Academy is one of the finest institutions which provides the best learning solutions handled by subject matter experts. These experts are backed by industry experience through which they empower the participants and creative professionals. They provide both the Blockchain and Bitcoin courses.

10 Tips to Improve your Performance at the interview

• Improve non-verbal gestures
• Dress for the Occasion
• Listen! Listen! Listen!
• Do not ramble on and on
• Familiarity is not always your friend so do not showcase your knowledge
• Utilise appropriate language
• An unwanted attitude can throw your interviewer off
• Don’t look desperate
• Ask questions

Recommended Reads

• Top 12 Blockchain Courses Online
• Top 10 Best Blockchain Certification Training Courses in India
• 20+ Blockchain Interview Questions and Answers
• The Future of Blockchain Technology
• Top 20 Blockchain Books

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FAQ’s

Ques 1. What is Blockchain technology?

Ans. Blockchain is a digital structure that records information. These are blocks that hold all the transactions in a disseminated form. Here nobody can cheat or hack as it ensures complete security and transparency. Above all, the information stored is not on a single computer. It distributes data across the network and protects from theft. 

Ques 2. What are the benefits of Blockchain?

Ans. Better transparency, cost-efficiency, and enhanced security are some of the benefits.

Ques 3.  What is distributed ledger technology?

Ans.  Many participants maintain records instead of one centralized computer.

Ques 4. What is the Ethereum blockchain?

Ans. It is a Blockchain technology that empowers the cryptocurrency Ether.

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