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

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.

Q 12. What are Block Identifiers?

In Blockchain, blocks can be identified by the block header hash and the block height.

Q 13. Is it possible in Blockchain to remove one or more block from the networks?

Yes, it can be done. There are times when only a specific portion of this online ledger is to be considered. With the help of default options and filters, this can easily be done without making a lot of efforts.

Q 14. What exactly do you know about the security of a block?

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.

Q 15. What are Merkle trees? How important are Merkle trees in Blockchains?

Merkle Tree also known as ‘hash tree’ is a data structure in cryptography in which each leaf node is a hash of a block of data, and each non-leaf node is a hash of its child nodes.Merkle tree-top blockchain interview questions-edureka
The benefit of using the Merkle Tree in blockchain is that instead of downloading every transaction and every block, a “light client” can only download the chain of block headers.
Also, if someone needs to verify the existence of a specific transaction in a block, then he doesn’t have to download the entire block. Downloading a set of a branch of this tree which contains this transaction is enough. We check the hashes which are just going up the branch (relevant to my transaction). If these hashes check out good, then we know that this particular transaction exist in this block.

Q 16. What is a ledger? Is Blockchain an incorruptible ledger?

Blockchain is considered incorruptible. Any ill-intentioned individual acting alone is powerless. “To take over the network, an attacker would have to control more than 50 percent of its total computing power,” Augier explains. “We hope that’s a theoretical scenario, but we can’t be sure. Should it happen, the individual would take every precaution to avoid being noticed.” Not to mention the energy required to power the computers needed for the blockchain system to work.

Q 17. Name the common type of ledgers that can be considered by users in Blockchain?

These are:
Q 18. How is a blockchain ledger different from an ordinary one?
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.

Q 19. What type of records can be kept in a Blockchain? Is there any restriction on same?

There is no restriction on keeping records of any type in the Blockchain approach. Industries are using Blockchain for securing all types of records.
The common types of records (to name a few) that can be kept on the Blockchains are:
  • Records of medical transactions
  • Identity management
  • Transaction processing
  • Business transactions,
  • Management activities
  • Documentation

Q 20. A distributed digital ledger is used for recording transaction in Blockchain. What does the system rely on?

The system relies on the network servicing protocol and the nodes of the network.

Q 21. Can You explain the components of Blockchain Ecosystem?

Following are the components of blockchain Ecosystem:

Blockchain_components-top blockchain interview questions-edureka

Q 22. State difference between proof-of-work & proof-of-stake?

proofofwork_proofofstake-top blockchain interview questions-edureka
                                                           Proof-of-work vs proof-of-stake

Q 23. Name some popular platforms for developing blockchain applications

After the development of bitcoin, various blockchain platforms started coming up. Ethereum came right after the evolution of Bitcoins, and is one of the popular public platforms for building Blockchain based applications.
Then there is a Hyperledger community for building enterprise-based solutions. Also, Qtum, IOTA, EOS are some of the widely used platforms for building Blockchain.