Top 51 Blockchain Interview Questions and Answers in 2022

Table of Contents

Blockchain Interview Questions and Answers

Also Read: Top 50 Groovy Interview Questions and Answers in 2022

1. What is Blockchain ?

Ans. Blockchain is a public ledger of a timestamped, ordered, and immutable list of all transactions on the bitcoin network.

2. Which is the smallest Bitcoin denomination ?

Ans. Satoshi

3. Which encoding is used for Bitcoin addresses ?

Ans. Base 58 encoding

4. Which language is used to describe about spending and transfer of bitcoins ?

Ans. Bitcoin uses a stack based language called script to describe the spending and transfer of bitcoins.

5. What is Unspent transaction output (UTXO) ?

Ans. It is an unspent transaction output that can be spent as an input to a new transaction.

6. What is Coinbase transactions ?

Ans. It is the first transaction in a block, always created by a miner.

7. What are transaction pools ?

Ans. Transaction pools are basically memory pools created in local memory by nodes in order to maintain a temporary list of transactions that are yet not confirmed in a block.

8. What are different types of transactions in Bitcoin ?

Ans. Below are the different types of standard transactions in Bitcoin:-

Pay to Public Key Hash (P2PKH)
Pay to Script Hash (P2SH)
MultiSig (Pay to Multisig)
Pay to Pubkey
Null data/OP_RETURN

9. Which Script is commonly used in Coinbase transactions ?

Ans. Pay to Public Key (P2PKH)

10. In which format transactions are encoded before transmitting over the bitcoin network ?

Ans. Hex format

11. When does Stale Blocks gets created ?

Ans. Stale blocks are created when a block is solved and every other miner who is still working to find a solution to the hash puzzle is working on that block.

12. What are Orphan Blocks ?

Ans. Orphan Blocks, also known as Stale Blocks are blocks that are not accepted in the blockchain network due to a time lag into the reporting of the block in question to the network of miners.

13. What is Mining in Blockchain ?

Ans. Mining is a resource-intensive process by which new blocks are added to the blockchain.

14. What is the time period for creating one new block ?

Ans. At an average one new block is created (mined) every 10 minute but sometimes blockchains create a new block as frequently as five seconds.

15. What is Hashing rate ?

Ans. The rate of calculating hashes per second is known as hashing rate.

16. What are different types of nodes in Bitcoin network ?

Ans. There are mainly two different types of node in the network:-

Full Nodes
SPV Nodes

17. What are Mining Nodes ?

Ans. Nodes which performs mining functions are called Mining nodes.

18. What are the functions performed by the Full Nodes ?

Ans. Full nodes mainly perform below four functions:-

Maintaining consensus with other nodes in the Network.
Verification of Transactions.
Holding and distributing copies of the entire blockchain ledger.
Serve as the information or redistribution relays

19. What is a Blockchain wallet ?

Ans. A blockchain wallet is a digital cryptocurrency wallet that holds all the private keys owned by the user.

20. Which of the ports are used by Bitcoin to establish network connection with the Peer ?

Ans. Bitcoin mainly uses two types of ports:-

p2p port (by default, 8333 in mainnet and 18333 in testnet)
RPC port (by default, 8332 in mainnet and 18332 in testnet)

21. Which is the most popular language used to write smart contracts for Ethereum Blockchain ?

Ans. Solidity

22. Who is Known as the Creator of Blockchain Technology ?

Ans. It was created by an unknown person goes with the name Satoshi Nakamoto.

23. What is Truffle ?

Ans. Truffle is the most popular development environment and testing framework for DApp developers.

24. What is MetaMask ?

Ans. MetaMask is a browser plugin that allows the normal browser to behave as a web3 browser, to interact with DApps, and to send transactions without running an Ethereum node.

25. What is Genesis Block ?

Ans. The initial block of the chain is known as Genesis Block.

26. Where can we store a Blockchain ?

Ans. Blockchain can be stored in either flat file or database format. For example, bitcoin uses LevelDB to store metadata about all the blocks that are downloaded to the disk.

27. How does all the blocks are connected in a Blockchain ?

Ans. Each block has a unique fixed size identifier called Hash. Since all the blocks are linked together by this hash value, each block will have the identifier of previous block.

28. Which algorithm is used to hash the block header in Bitcoin ?

Ans. SHA256 Hashing Algorithm

29. What's the meaning of height in a blockchain ?

Ans. Height is nothing but the distance of the block, or the block count from the genesis block.

30. What are different sections each block contains ?

Ans. Each block contains the following section:-

Block Size
Block Header
Transaction Counter
Transactions

31. Does the block hash is a hash value of entire block ?

Ans. No, It is only the hash value of block header and Transactions.

32. What are different structure components of a Block Header ?

Ans. Block Header has below structural components:-

Version
Previous Block Hash
Merkle Root
Timestamp
Difficulty Target
Nonce

33. What is the value of a Merkle Hash Tree ?

Ans. Merkle root is the value of the Merkel Hash Tree. More about Merkle Tree

34. What are the disadvantages of using Blockchain Technology ?

Ans. Below are few of the disadvantages:-

Blockchain cannot go back as data is Immutable.
It is harder to scale due to their consensus method.
Mining is an energy intensive process which requires huge amount of energy.
As the transactions grow, storage could pose a problem.
Users need to maintain their own wallet hence self maintenance is required.
Requires expertise knowledge to implement blockchain technology.
It still requires lot of maturity as implementation is a costly process.

35. What is Byzantine General's Problem, or Byzantine failure ?

Ans. It is a fault which occurs when there is a loss of a service in a system that needs to achieve a consensus. This kind of failure is witnessed in distributed systems, where it is difficult to gather information about the status of components, and the presence of bad actors makes it more difficult to reach a consensus.

36. Which algorithm was used to solve the Byzantine failure problem ?

Ans. It was solved by using a consensus algorithm called Proof of Work.

37. How does asset owners prove their Identity ?

Ans. The asset owners prove their identity by signing the transactions using their private key.

38. Who will be able to claim the asset in a Bitcoin network ?

Ans. The one who will be having the Private Key.

39. What are SPV nodes ?

Ans. It stands as Simplified Payment Verification node which will be used for payment verification without needing to download the entire blockchain.

40. What are different types of Blockchain wallets ?

Ans. Wallets are categorized into two types based on the way key is created:-

Non-deterministic Wallet
Deterministic Wallet

41. What is Non-deterministic wallet ?

Ans. A non-deterministic wallet is a collection of randomly created private keys that bear no relation to each other.

42. What is Deterministic wallet ?

Ans. A deterministic wallet is also called a seed wallet because all the keys in this wallet are derived from a single seed.

43. What is the major disadvantage in using Non-deterministic wallet ?

Ans. Since Non-deterministic wallet contains randomly created private keys which bears absolutely no relation to each other, it is extremely difficult to reconstruct in the event that they are lost.

44. What is Block validation ?

Ans. It is a process of checking whether the latest block has a pointer or hash reference pointing to the previous block.

45. What is Block Synchronization ?

Ans. It is a process under which each node that joins the blockchain network needs to update its local copy of blockchain to synchronize its state with the global state of the rest of the network.

46. What is Soft fork ?

Ans. When a node receives different versions of a block of the same height, it will add one of them to the blockchain based on the order of arrival and either rejects the other or keeps it in a memory pool. Due to this, nodes in the network might end up with different versions of the blockchain. This is called a temporary fork or a soft fork.

47. What are different types of interfaces blockchain application provides ?

Ans. It usually provides two types of interfaces:-

HTTP API Interface
Web Socket Interface

48. What is NEO ?

Ans. NEO is a blockchain platform and cryptocurrency that facilitates the creation and management of digital assets and smart contracts.

49. Where does Cryptocurrency exchange store most of their coins ?

Ans. Exchanges store most of their coins in hot storage so that withdrawals can be performed instantly.

50. What is ICO ?

Ans. It stand as Initial Coin Offering, is the cryptocurrency industry's equivalent to an Initial Public Offering (IPO). A company looking to raise money create a coin and launches it as ICO.

51. What is 51% attack ?

Ans. If a participant in the network is able to control more than 50% of the resources required to reach the consensus to create blocks, then the block creation mechanism can be manipulated by that participant. The 51% attack can be performed on any of the consensus algorithms, but it is generally used in Proof of Work-based blockchain networks.

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