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The Best Blockchain Interview Questions And Answers (Updated 2018)

blockchain developer interview questions

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

Answer:

Well, a block or the entire blockchain is protected by a strong cryptographic hash algorithm. Each block has a unique hash pointer. Any modification in the block constituents will result in the change in the hash identifier of the block. Therefore, it offers an excellent level of security. Thus, one needs not to worry about the safety as well as the security of data that is present in a block.(blockchain interview questions and answers)

2. How is a blockchain ledger different from an ordinary one?

Answer:

The first and in fact the prime difference is Blockchain is a digital ledger that can be decentralized very easily. The chances of error in this approach are far less than that in an ordinary ledger. An ordinary ledger is what that is prepared by hands or by human efforts while the Blockchain performs all its tasks automatically. You just need to configure it in a proper manner and by following all the guidelines.

3. Why Blockchain is a trusted approach

Answer:

Blockchain can be trusted due to several reasons. The very first thing is its compatibility with other business applications because of its open-source nature. Second one is its security. As it was intended for online transactions, the developers have paid special attention in keeping up the pace when it comes to its security. It really doesn’t matter what type of business one owns, Blockchain can easily be considered.

4. What is Transparent and incorruptible in blockchain?

Answer:

The blockchain network lives in a state of consensus, one that automatically checks in with itself every ten minutes. A kind of self-auditing ecosystem of a digital value, the network reconciles every transaction that happens in ten-minute intervals. Each group of these transactions is referred to as a “block”. Two important properties result from this:
Transparency data is embedded within the network as a whole, by definition it is public. It cannot be corrupted altering any unit of information on the blockchain would mean using a huge amount of computing power to override the entire network.

5. How is a blockchain ledger different from a standard one?

Answer:

The first and of course the prime distinction is Blockchain is a digital ledger which will be decentralized terribly simply. The probabilities of error during this approach are way under that in a standard ledger. An ordinary ledger is what that’s ready by hands or by human efforts whereas the Blockchain performs all its tasks mechanically. You simply have to be compelled to assemble it in an exceedingly correct manner and by following all the rules.(Online Training Institute)

6. In Blockchain, blocks are linked in what series?

Answer:

In Blockchain Blocks are arranges within the Backward to the previous block series. (blockchain interview questions and answers)

7. Explain the importance of blind signature and the way it’s useful?

Answer:

It is a type of digital signature within which the content of a message is disguised (blinded) before it’s signed. The ensuing blind signature may be publically verified against the first, unblinded message within the manner of a daily digital signature.

Blind signatures are generally used in privacy-related protocols where the signer and message author are totally different parties. Examples include cryptographic election systems and digital money schemes.

8. What is the average block size in Ethereum?

Answer:

Around 2KB, although it depends. Ethereum has a gas limit rather than a block size. The gas limit is a cap on both processing and storage/bandwidth because the cost of a transaction/function is fixed in units of gas for each type of instruction.

The gas limit is voted up or down by each miner and each miner determines what gas price it is willing to accept which is like bitcoin transaction fees but on a per gas basis rather than a per transaction basis.

To figure out how many transactions can fit in a block you don’t need to know what the price of gas is. You just need to know how much gas a transaction uses and divide the gas limit by that.

If the network receives a load of spam transactions that start filling up blocks then miners have 2 choices. They can vote up the gas limit to fit in more transactions or they can start increasing the gas price and reject transactions that pay too low a fee. Like with bitcoin a transaction with a low fee might still get through but it would have to wait until a miner that accepts a lower fee (lower gas price) is willing to let it in.

With a sustained spam attack it would just get progressively more costly to do transactions until either the spammer runs out of money or the miners make so much money that they start expanding the network capacity

9. How mining in Ethereum works?

Answer:

How mining works

Today, ethereum’s mining process is almost the same as bitcoin’s.

For each block of transactions, miners use computers to repeatedly and very quickly guess answers to a puzzle until one of them wins.

More specifically, the miners will run the block’s unique header metadata (including timestamp and software version) through a hash function (which will return a fixed-length, scrambled string of numbers and letters that looks random), only changing the ‘nonce value’, which impacts the resulting hash value.

If the miner finds a hash that matches the current target, the miner will be awarded ether and broadcast the block across the network for each node to validate and add to their own copy of the ledger. If miner B finds the hash, miner A will stop work on the current block and repeat the process for the next block.

It’s difficult for miners to cheat at this game. There’s no way to fake this work and come away with the correct puzzle answer. That’s why the puzzle-solving method is called ‘proof-of-work’.

On the other hand, it takes almost no time for others to verify that the hash value is correct, which is exactly what each node does.

Approximately every 12–15 seconds, a miner finds a block. If miners start to solve the puzzles more quickly or slowly than this, the algorithm automatically readjusts the difficulty of the problem so that miners spring back to roughly the 12-second solution time.

The miners randomly earn these ether, and their profitability depends on luck and the amount of computing power they devote to it.

The specific proof-of-work algorithm that ethereum uses is called ‘ethash’, designed to require more memory to make it harder to mine using expensive ASICs — specialized mining chips that are now the only profitable way of mining bitcoin.

In a sense, ethash might have succeeded in that purpose, since dedicated ASICs aren’t available to mine ethereum (at least not yet).

Furthermore, since ethereum aims to transition from proof-of-work mining to ‘proof of stake’ — which we discuss below — buying an ASIC might not be a smart option since it likely won’t prove useful for long.(The Best blockchain interview questions for freshers)

10. So what is a Smart Contract?

Answer:

It is computer code written in multiple languages. Smart contracts live on the network. They enforce rules and perform actions, negotiated by participants in those contracts.

11. Why would you have a private network?

Answer:

There are many reasons, but mainly because of data privacy, distributed database, permissions control and testing.

12. Can you make a case for what square measure off-chain transactions?

Answer:

Off-chain dealing is that the movement of value outside of the blockchain. while associate on-chain dealings – usually observed as merely ‘a transaction’ – modifies the blockchain associated depends on the blockchain to see its validity an off-chain transaction depends on alternative ways to record and validate the transaction.(Blockchain Training)

13. Why does it cost money to invoke a method on a Smart Contract?

Answer:

Some methods, which do not modify the state of the contract and have no logic other than returning a value, are free.
Apart from sending ether as a payment, invoking methods that make change the state cost money also because they require gas for execution. (blockchain interview questions and answers)

14. What exactly do you know about executive accounting? Does Blockchain support the same?

Answer:

Executive accounting is nothing but a special type of accounting which is designed exclusively for a business that offers services to the people. There is no strict upper limit on services and a business can manage any through the executive accounting. Blockchain has algorithms that are specially meant to handle executive accounting. In fact, it cut down many problems that are associated with the same.

15. Name the steps that are involved in the Blockchain project implementation?

Answer:

Well, there are total six steps involved in this process and they are:

  • Requirement identification
  • Screen ideas consideration
  • Project development for Blockchain
  • Feasible study on the security
  • Implementation
  • Controlling and monitoring the project

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

Answer:

There is no restriction of keeping records in the Blockchain approach. It must be noted that the record keeping is not just limited to these applications only.

The common types of records that can be kept on them are:

1. Records of medical transactions
2. Identity management
3. Transaction processing
4. Events related to organizations,
5. Management activities
6. Documentation

17. What do you mean by blocks within the Blockchain Technology?

Answer:

Blocks are used to store the list of records that is Blockchain and are successively associated with all other blocks, thus represents a series known as Blockchain.

18. What is Secret Sharing? Will it have any benefit in Blockchain technology?

Answer:

It is a widely known indisputable fact that security matters tons in digital transactions. Secret sharing is associate approach meant for same. In Blockchain technology it’s an associate approach that divides secret or personal data into totally different units and sent them to the users on the network.(blockchain interview questions and answers)

The original data will solely be mixd once a participant to whom a share of the key is allotted conform to combine them at the side of others. Their square measure many security-related edges it offers in Blockchain technology.(WebSphere Video Training)

19. Explain proof of stake in a simple way?

Answer:

The creator of the block is chosen randomly by means of wealth and age (stake). It is not computationally intensive.

20. You mentioned something about indexes. What determines the account index?

Answer:

The order in which you add the accounts.

21. Why is there gas, more precisely?

Answer:

Since miners execute contract code on their machines, they must cover their costs from executing the code requested by a caller.

22. What is a DApp and why is it different than a normal App?

Answer:

An App usually consists of a client which communicates to some centralized resources (owned by an organization).
There is a mid-tier connecting to a centralized data tier. If information in the centralized data tier is lost, it cannot be recovered (easily).
DApp means Decentralized Application. DApps interact with the network via Smart Contracts. The data they work with resides in the contract instance.
Centralized data can be compromised more easily than decentralized.(Amazon Web Services Training)

23. What is a trapdoor function, and why is it needed in blockchain development?

Answer:

A trapdoor function is a function that is easy to compute in one direction but difficult to compute in the opposite direction unless you have special information. Trapdoor functions are essential for public key encryption—that’s why they are commonly used in blockchain development to represent the ideas of addresses and private keys.(Company)

24. What are the key principles that need to be followed to make blockchain secure?

Answer:

Even though blockchain is secure, it still needs to be implemented correctly. The following principles need to be followed for proper implementation.

  • Auditing
  • Security testing
  • Securing applications
  • Continuity planning
  • Database security
  • Digital workforce training.

25. How does blockchain work?

Answer:

Blockchain works as follows:

1. Transaction: Two parties who are part of the blockchain network exchange data. The data can be money, contracts, deeds or any asset that can be represented digitally.

2. Verification: The nodes or computers in the network verify if the transaction is valid based on rules preset on the network.

3. Block: The transaction is added to a block in the network. Each block is identified by a hash generated by an algorithm agreed upon by the network.

4. Mining and validation: Miners validate a block by solving a mathematical puzzle.

5. After the block is validated, it is distributed to all nodes through the network. Each node adds the block to the majority blockchain.

26. How are merkle trees used in Blockchains?

Answer:

Blocks in a Blockchain contain transactional data that must be secure, tamper proof and maintained in a chronological order. Blockchain uses Merkle trees to achieve these requirements.

The transactions in a block are hashed and and encoded into a Merkle tree.

Interview: Azeem Malik, Business Development – IBM Food Trust, IBM Blockchain
Future Food-Tech New York spoke to Azeem Malik, Business Development of IBM Food Trust, IBM Blockchain about the company’s blockchain strategies, opportunities for food businesses incorporating blockchain into their system and success stories that have impacted the food industry.(blockchain interview questions and answers)

27. What is the difference between Bitcoin and Blockchain?

Answer:

Bitcoin is a payments application on top of a blockchain network. Blockchain is the technology behind bitcoin. Think of the blockchain network as a train track and the application on top of the network as the railcar. Bitcoin is a railcar (application) on the blockchain train track (network). There are several different tracks out there, or blockchain networks, designed to solve different problems and engage different types of users. The IBM Blockchain Platform is an example of a blockchain network that developers can build applications on top of.

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

Answer:

No, it’s not possible to do so. In case any modification is required, the organization simply has to erase the information from all other blocks too. It is because of no other reason than this, data must be given the extreme care of while using this approach.

29. What do you know about Blockchain? What is the difference between Bitcoin blockchain and Ethereum blockchain?

Answer:

The blockchain is a decentralized distributed database of immutable records. The technology was discovered with the invention of Bitcoins(the first cryptocurrency). It’s a trusted approach and there are a lot of companies in the present scenario which are using it. As everything is secure, and because it’s an open source approach, it can easily be trusted in the long run.

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

Answer:

Every block in this online ledger basically consists of a hash pointer which acts as a link to the block which is prior to it, transaction data and in fact a stamp of time.

31. Name organizations that can use Blockchain technology?

Answer:

There is no strict upper limit on the category of business who can consider this approach. The fact is almost all the businesses are engaged in online or financial transactions that they need to make to run the processes smoothly. Large scale corporations, financial institutions, private businesses, government departments and even defense organizations can trust this technology very easily.(blockchain interview questions and answers)

32. What are the key principles in Blockchain that are helpful in eliminating the security threats that needs to be followed?

Answer:

Yes there are a few principles that need to be followed with respect to time. They are:

  • Auditing
  • Securing applications
  • Securing testing and similar approaches
  • Database security
  • Continuity planning
  • Digital workforce training

All these principles are basic and are easy to implement. They are helpful in making the transactions records useful.

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

Answer:

It is a well-understood that security matters a lot in digital transactions. Secret sharing in Blockchain technology is an approach that divides secret or personal information into different units and sent them to the users on the network. The original information can only be combined when a member to whom a share of the secret is allocated agree to combine them together with others. There are several security-related advantages it can offer in Blockchain technology.

34. Why do we need decentralized systems? Benefits of Blockchain Technology?

Answer:

Decentralization benefits in various ways they are:

Entitle users: Decentralized systems enables users to keep control of all their digital transactions.

Fault tolerance: Decentralized systems helps in controlling fault tolerance because they are less likely to fail accidentally.

Durability and robustness: Blockchain doesn’t contain centralized system. It’s distributed and it’s very hard to attack and more expensive to destroy or manipulate.

Free from frauds: It’s very much tough in decentralized systems to commit frauds and scams to benefit from the system.

Faster transaction time: Blockchain and decentralized technology enable users to do transactions faster and reduce time to minutes when compared to normal bank transactions.

Lower cost for transactions: Decentralized systems like Blockchain get rid of third-party intermediaries and transaction costs, and service charger for exchanging assets. This greatly reduces the transaction fees and benefits users.

Provides lucidity: Blockchain is very transparent technology, the data can be publicly viewable, and all transactions can’t be altered or deleted.

Data authenticity: In a decentralized system like blockchain data is complete, consistent, timely, accurate, and widely available over the network.

35. What is a Blockchain client?

Answer:

A Blockchain client is referred to any node able to parse and verify the blockchain, its smart contracts and everything related. It also allows you/provides interfaces to create transactions and mine blocks which is the key for any blockchain interaction.

36. What is block time in Blockchain?

Answer:

The block time is the average time it takes for the network to generate one extra block in the blockchain.[38] Some blockchains create a new block as frequently as every five seconds. By the time of block completion, the included data becomes verifiable.

37. What is a merkle tree in blockchain?

Answer:

A Merkle tree is designed to ensure blocks of data can receive from other peers in a peer to peer network. More specifically, this information needs to be in its original state, without alterations or corrupted information.

In most cases, a Merkle tree comprises of two child nodes under each node on the network. This binary approach reinstated, although it still leaves a lot of room for future improvements. In fact, there does not appear to be a limit as to how many child nodes can be used per node to establish a more secure Merkle tree.

38. What type of records blockchain supports? Is there any restriction for record keeping?

Answer:

The blockchain supports has no parity when it comes to recording data or records of any type. This means that blockchain can have multiple use cases for different industry and verticals. Anyone from startups to industries running supply chain management can use blockchain to store data and utilize the power of blockchain to their advantage.

Some of the examples of blockchain record include the following:

  • Medical records
  • Supply chain management records
  • Employee records
  • Transaction/eCommerce records
  • Management records
  • Documentation
  • Music records
  • And so on.

39. What is the difference between blockchain and distributed ledger?

Answer:

Distributed ledger is a database which consists of nodes that are connected in a network. It is used to store data where each node plays a crucial role by having a copy of the data itself. Blockchain, on the other hand, is a type of distributed ledger platform which makes use of it and provides an extra layer of accuracy and security to the whole network.

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