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Top Blockchain Interview Questions and Answers

Updated: Dec 30, 2021



We have Collected top Blockchain Interview and Viva Questions for Everyone. These Question can help everyone including Students who have Blockchain as Course in their Semester. We have tried to cover all the Important topics in Blockchain with brief Explanation. This all Question are from Top Websites and We have given them as References. We appreciates everyone who want to add this blog.

1. What is Blockchain technology?


The blockchain is an incorruptible digital ledger of economic transactions that can be programmed to record not just financial transactions but virtually everything of value.



2. What is Blockchain Wallet and How Does It Work?


A blockchain wallet is a piece of digital software that stores private and public keys, as well as tracks and records all transactions involving those keys on the blockchain. A blockchain wallet, in theory, does not store cryptocurrency; instead, all records belonging to these keys are stored on the blockchain on which the wallet is hosted. Blockchain wallets have public and private keys. A public key and a private key are used in a similar way in blockchain wallets. A public key is similar to an email address in that it can be shared with others. When your wallet is created, a public key is created as well, which you can share with others to obtain funds. The private key is a closely guarded secret. It’s similar to your password in that it shouldn’t be compromised, and you shouldn’t share it.



3. What Is Ethereum (ETH)?


Ethereum is an open-source software platform based on Blockchain technology that enables developers to build and deploy decentralized applications (i.e., applications that are not controlled by a single entity). You may construct a decentralized application in which the participants are the ones who make the decisions.



4. What is the difference between Bitcoin blockchain and Ethereum?


Although bitcoin and ether are both digital currencies, the ethereum blockchain differs significantly from the bitcoin blockchain. Bitcoin was created solely for the purpose of being a digital currency. whereas ethereum blockchain is a broader version of blockchain technology. And it is a distributed ledger technology that organizations are using to create new services, however, ethereum is much more stable than bitcoin.



5. What are Smart Contracts and how do they work?


A smart contract is a computer code-based agreement between two individuals. They are stored on a public ledger and cannot be modified because they run on the blockchain. A smart contract’s transactions are handled by the blockchain, which means they can be submitted automatically without the involvement of a third party. The Smart contracts are secure, transparent, third-party-free, autonomous, and accurate. Let me use an example to demonstrate how smart contracts work. If Alex decides to sell his home to Bob. Then they would pay a slew of fees to third parties such as real estate agents, banks, and attorneys, and others. However, with a smart contract, they can simply write a statement stating that if Bob pays this amount of money, he will be given ownership of the property. Hence, smart contracts can cut down the actual process and give us trustable options for transactions.



6. What Is Cryptocurrency Mining and how Bitcoin mining works?


The word “crypto mining” refers to the process of obtaining cryptocurrencies by the use of computers to solve cryptographic equations. Validating data blocks and applying transaction records to a public record (ledger) is also a part of this method. Bitcoin mining is not just the process of putting new bitcoins into circulation, but it is also an important part of the blockchain ledger’s upkeep and growth. It is carried out with the assistance of highly advanced computers that solve extremely difficult computational math problems.



7. What is a Blockchain Explorer?


A blockchain explorer is a piece of software that draws data from a blockchain using an API and a blockchain node, then uses a database to organize the data and present it to the user in a searchable format.



8. What Is Hashing in Blockchain?


The process of making an input item of any length represents an output item of a fixed length is referred to as hashing in the blockchain. Take, for example, the use of blockchain in cryptocurrencies, where transactions of varying lengths are run through a given hashing algorithm and all produce a fixed-length performance.



9. What are the different types of Blockchain?


The blockchain is classified into four types

  • Public Blockchains

  • Private Blockchains

  • Consortium Blockchains

  • Hybrid Blockchains.



10. What are the benefits of Blockchain Technology?


Blockchain technology has the following benefits:

  • Blockchain technology employs advanced security compared to other networks or record-keeping systems. Prior to being recorded, all transactions must be agreed upon. A transaction is encrypted and connected to the previous transaction after it has been authorized.

  • Blockchain offers transparency. As one of the major problems in the new industry is transparency. An organization may use blockchain to create a completely decentralized network that eliminates the need for a centralized authority, increasing the system’s transparency.

  • Blockchain helps in reducing costs. Organizations will save a lot of money by using the blockchain instead of paying third-party vendors.

  • Blockchain automates time-consuming processes in order to increase performance. With the aid of automation, it also eliminates human errors. As a result, blockchain increases efficiency and speed.

  • The blockchain allows for immediate traceability. It generates an audit trail that records an asset’s provenance at each stage of its journey which prevents fraud.

11. Name some popular Blockchain Platforms for Blockchain Applications?

The following are the list of widely-used platforms for blockchain-based applications

  • IBM Blockchain

  • EOS

  • OpenLedger

  • Corda

  • Ripple

  • Ethereum

  • IOTA

  • Quorum

  • OpenChain

  • Hyperledger Sawtooth


12. What is the difference between Blockchain and Hyperledger?


  • Blockchain is a technology that allows us to build decentralized systems. When we break down blockchain, the “block” refers to information stored in a digital format, while “chain” refers to the database where that information is stored.

  • Hyperledger is a type of blockchain platform. It’s a blockchain-based open-source network. These blockchains each have their own storage routines and consensus, as well as smart contracts, identity, and access management.

  • Since hyperledger is a product of the blockchain platform, they have a few in common. However, due to hyperledger’s unique features, both are different.

  • Mostly, blockchain is classified into public and private types. And Hyperledger is an example of private blockchain.


13. What are some of the popular Cryptocurrencies?


The most popular Cryptocurrencies are:

  • Bitcoin(BTC)

  • Ethereum(ETH)

  • Ripple(XRP)

  • Litecoin(LTC)

  • Bitcoin Cash(BCH)


14. What is a ledger? What is the difference between a distributed ledger and a traditional ledger?


A ledger is a constantly growing file. It maintains a permanent record of all transactions between two parties on the blockchain network.

A distributed ledger is a database of digital data that is replicated, exchanged, and synchronized across multiple sites in a network.

Distributed ledgers, unlike traditional ledgers (think banks, governments, and accountants), provide a system of synchronized databases that have an auditable background of information that is accessible to everyone inside the network.


15. What is a 51% Attack?


A miner or a group of miners attempting to control more than 50% of a network’s hashing capacity, processing power, or hash rate is known as a 51 percent attack on a blockchain network. The attacker may prevent new transactions from taking place or being verified in this attack. They can also reverse transactions that have already been verified while in charge of the network, resulting in a double-spending problem.


16. Compare Blockchain with relational database


CriteriaBlockchainRDBMSUnit of dataBlockTableSingle point of failureDoes not existExistsCentralized controlNoYesEditing/deleting dataNot possiblePossible


17. What do you mean by blocks in Blockchain technology?


In the Blockchain, a block is simply a set of records. The term “blockchain” refers to the process of joining these lists together. For example, if a company has 100 ledger books, the total is known as Blockchain, and each ledger is referred to as a block.


18. How does a block is recognized in the Blockchain approach?


Any block in this online ledger consists primarily of a hash pointer that serves as a connection to the previous block, transaction data, and a time stamp.


19. Are there any network-specific conditions for using Blockchain technology in an organization?


No, there isn’t any such restriction on using it. However, under the worried protocols, the network must be a peer-to-peer network. It effectively validates the new block and assists businesses in keeping up with the pace in this area without relying on third-party applications.


20. Is it possible to modify the data once it is written in a block?


No, it is not possible to do that. If any customization is needed, the company simply needs to delete the details from all other blocks as well. Data must be treated with extreme caution when using this system for no other reason than this.


21. What type of records can be kept in Blockchain? Is there any restriction on the same?


In the Blockchain method, there are no limitations on the number of records that can be held. It is important to remember that record keeping is not limited to these applications.

The following are examples of the types of information that can be held on them:

  1. Health transaction records

  2. Managing your identity

  3. Production of transactions

  4. Organizational events and management tasks

  5. Documentation is required.


22. How Does Blockchain Create Blocks?


When the block size is reached, the blockchain creates blocks automatically. Since the block is a file, the transactions are saved until the file is complete. They are linked in such a way that the most recent block is connected to the previous one. A hash value is created using a mathematical function to identify a block. It also shows any modifications made to a block.


23. Can Anyone Remove Blocks from A Blockchain?


The manner in which blocks are removed from a blockchain is entirely dependent on how they are treated. Manually removing a block is not possible. If it is destroyed, however, the blockchain may attempt to restore the database using other peers.

They can be removed after they’ve been checked to reduce the blockchain’s size since they don’t need someone to perform regular operations. It can be re-downloaded if necessary. This process is called pruning.


24. What is encryption? What is its role in Blockchain?


Encryption is a technique that is used to keep the data secure. The data is encoded to some level before being sent out of a network by the sender in this process. Only the receiver will be able to decode it. This approach is useful in Blockchain because it simply adds to the overall protection and validity of blocks, making them more stable.


25. What exactly do you know about the security of a block?


Any users on a network cannot customize a block. As a result, it offers a high degree of security. Furthermore, every block is protected by cryptography, which is yet another vote in this case. As a result, there is no need to be concerned about the protection of data in a block.


26. Why is Blockchain a trusted approach?


For a variety of purposes, blockchain can be trusted. Because of its open-source existence, the first thing that comes to mind is its compatibility with other business applications. The second factor is its safety. Since it was designed to be used for online transactions, the developers paid particular attention to keeping up with the times in terms of protection. Blockchain will help despite the type of company one owns.


27. What is Secret Sharing? Does it have any benefit in Blockchain technology?


It is completely obvious that security is extremely important in digital transactions. In Blockchain technology, secret sharing is a method of dividing secret or personal information into smaller units and sending them to network users. The original knowledge can only be merged with others if a person who has been assigned a share of the secret decides to do so. In Blockchain technology, there are a number of security benefits it can provide.


28. What are Blockchain Durability and robustness?


Bitcoin was founded in the year 2008. Since then, there has been no major damage to the Bitcoin network. For nearly 30 years, the internet has proved to be a reliable resource. It’s a track record that bodes well for the future development of blockchain technology.

In the same way, as the internet has built-in robustness, blockchain technology does as well. The blockchain can’t be managed by any single individual since it stores blocks of information that are similar across its network. There should be no single failure point in the blockchain.


29. How does Bitcoin use Blockchain?


A transaction is a value transfer that is recorded in the blockchain between Bitcoin wallets. Bitcoin wallets store a private key, also known as a seed, which is used to sign transactions and provide mathematical proof that they came from the wallet’s owner.


30. Is Blockchain an incorruptible ledger?


Yes, Blockchain is an incorruptible ledger. According to the inventor, the blockchain database cannot be tampered with.


31. What are blockchain requirements?


Blockchain is a truly disruptive technology that has the potential to change business networks. So, the requirements for a blockchain is as follows:

  • Smart contracts

  • Ledgers

  • Cryptography

  • Consensus Protocol


32. In what order are the blocks linked in the blockchain?


Each block in the blockchain is always linked in reverse order. To put it another way, blockchain connects each block to the one before it. Hence, blocks are linked in the backward direction.

That’s it for the list of top Blockchain questions for beginners. Let’s move to the next section of intermediate Blockchain Technology interview questions.


Intermediate Blockchain Interview Questions


33. What are Block Identifiers?


A blockchain has a unique identifier for each block. The hash value is used to create a unique identifier. As a result, no two block identifiers would be the same. In Blockchain, blocks can be identified by the block header hash and the block height.


34. Name the common type of ledgers that can be considered by users in Blockchain?


There are three common types of a ledger that can be considered by users in the blockchain:

  1. Centralized Network