Ibm Blockchain Interview Questions Pdf

1. What are the blockchain requirements?
Answer: Blockchain is a truly disruptive technology that can transform business networks. We also believe that this innovation has to happen in the open, collaborating with other technology companies and industries. To this end, IBM continues to contribute code to the Hyperledger Project.

From IBM’s perspective, industrial-grade blockchain technologies have the following characteristics:

A shared, permissioned ledger is the append-only system of record (SOR) and a single source of truth. It is visible to all participating members of the business network.
A consensus protocol agreed to by all participating members of the business network ensures that the ledger is updated only with network-verified transactions.
Cryptography ensures tamper-proof security, authentication, and integrity of transactions.
Smart contracts encapsulate participant terms of agreements for the business that takes place on the network; they are stored on the validating nodes in the blockchain and triggered by transactions.

2. Is it possible to switch the data once it’s written in an exceeding block?
No, it’s impossible to do so. Just in case any modification is needed, the organization merely has to erase the knowledge from all different blocks too. Because of as a result of no different reason than this, knowledge must be given the acute care of while mistreatment this approach. (E learning Portal)

3. What are the Merkle trees? How vital are Merkle trees in Blockchains?
Merkle Tree additionally called ‘hash tree’ is a data structure in cryptography during which every leaf node could be a hash of a block of knowledge, and every non-leaf node could be a hash of its kid nodes.

if somebody has to verify the existence of selected dealing in an exceedingly block, then he doesn’t need to transfer the complete block. Downloading a collection of a branch of this tree that contains these dealings is enough. We tend to check the hashes we are simply rising the branch (relevant to my transaction). If these hashes consider sensible, then we all know that these specific dealings exist during this block.

4. Name some widespread platforms for developing blockchain applications?
After the event of bitcoin, numerous blockchain platforms started arising. Ethereum came right once the evolution of Bitcoins and is one in all the favored public platforms for building Blockchain primarily based applications.

Then there’s a Hyperledger community for building enterprise-based solutions. Also, Qtum, IOTA, EOS are a number of the widely used platforms for building Blockchain.

5. What is Geth’s “fast” sync, and why is it faster?
Instead of processing the entire blockchain one link at a time and replay all transactions that ever happened, fast sync downloads transaction receipts along with the blocks and pulls an entire recent state database.

6. What is Remix?
An online tool for developing, testing and deploying contracts. It’s great for quickly building and testing lightweight contracts but not for more complex ones.

7. What is a chain fork?
Blocks in the ledger are included in such a way as to build the longest chain, i.e., the chain with the greatest cumulative difficulty. Forking is a situation where two candidate blocks are competing to form the longest blockchain and two miners discover a solution to the proof-of-work problem within a short period from each other. The network is then divided because some nodes get blocks from miner #1 and some from miner #2. 

A fork usually gets resolved in one block, because the probability that this situation happens again gets extremely lower with the next blocks that arise, so soon there is a new longest chain that will be considered as main.

8. How is a block recognized within the Blockchain approach?
Every block during this online ledger essentially consists of a hash pointer that acts as a link to the block that is before it, transaction knowledge and a stamp of time.

9. Name the common sort of ledgers which will be thought of by users in Blockchain?

These are:

  • Centralized Distribution
  • Decentralized distribution
  • Distributed network
  • Follow the link to know more about Ledger

10. Example of a Smart Contract use case?
A popular Seller-Buyer scenario where a Buyer deposits money in the smart contracts, Seller sees the deposit and sends the goods, Buyer receives the goods and releases the payment.

11. Does gas price determine when a transaction is processed?
Yes and no. The higher the gas price, the more likely your transaction will be mined. Despite, gas price is not a guarantee for faster transaction processing. 

12. What is the very first thing you must specify in a Solidity file?
The version of the Solidity compiler, which is specified as ^0.4.8. It is necessary because it prevents incompatibility errors which can be introduced when compiling with another version.

13. How DApps are different from Smart Contracts?
Apps are a ‘blockchain enabled’ website, where the Smart Contract is what allows it to connect to the blockchain. The easiest way to understand this is to understand how traditional websites operate. 

The traditional web application uses HTML, CSS, and Javascript to render a page. It will also need to grab details from a database utilizing an API. When you go onto Facebook, the page will call an API to grab your data and display them on the page. Traditional websites:  Front End → API → Database
dApps are similar to a conventional web application. The front end uses the same technology to render the page. The one critical difference is that instead of an API connecting to a Database, you have a Smart Contract connecting to a blockchain. dApp enabled website:  Front End → Smart Contract → Blockchain
As opposed to traditional, centralized applications, where the backend code is running on centralized servers, dApps have their backend code running on a decentralized P2P network. Decentralized applications consist of the whole package, from the backend to the frontend. The smart contract is only one part of the app:

Frontend (what you can see), and
Backend (the logic in the background).
A smart contract, on the other hand, consists only of the backend, and often only a small part of the whole dApp. That means if you want to create a decentralized application on a smart contract system, you have to combine several smart contracts.

14. How do verifiers check if a block is valid?
Every full node on the network does block verification. When a new block is announced, every node that receives it does a list of checks. The two most important checks are of proof of work (if a block provides enough work to be included in the chain) and of the validity of all transactions

15. Explain the principle of Blockchain Technology?
The basic principle of Blockchain technology is that it permits the information to be dispersed in the users while not being monitored.

16. What are the methods that are used in attacking the RSA algorithm?

The methods that are used in assaultive the RSA algorithms are:

Mathematical attacks: In this attack, we tend to square measure mistreatment different methods, that is similar in the effort to issue the merchandise of 2 primes
Brute force: It includes all potential secret keys (Company)

17. What are the key components of a blockchain ecosystem?

Following are the key components of a blockchain ecosystem:

1. Node application: Every computer that is part of a blockchain ecosystem must install and run an application. For example, in the Bitcoin network, every computer must install and run the Bitcoin wallet application.

2. Shared ledger: the Shared ledger is the data structure (Blockchain) that is distributed across all the nodes of a blockchain network. The shared ledger can be managed and viewed through the node application that runs on every computer in the network.

3. Consensus algorithm: Consensus algorithm is an algorithm implemented as part of the node application which provides the rules on how the blockchain network arrives at a single view of the shared ledger.

4. Virtual machine: Virtual machine is a logical part of the node application. The virtual machine understands a wide range of instructions, manages the state of digital contracts and enforces the terms of the contract.

18. Where have you seen the greatest success in how blockchain has impacted the food industry so far? Are there any case study examples you can share?
Blockchain has empowered industry leaders to imagine new possibilities when it comes to the way they run their businesses and operate their supply chains. It has also brought competitors to the same table to agree to collaborate along with the same networks and work together to move the industry forward towards transparency and greater information flow.

One of the first use cases that IBM and Walmart piloted was tracing back a pack of sliced mangoes from a Walmart store shelf to its source. Using their existing traceability solutions, it took Walmart’s food safety team 6 days, 18 hours, and 26 minutes to get back to source information. The same use case on IBM blockchain technology took 2.2 seconds. 

19. Is it possible in Blockchain to remove one or more blocks 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 effort.

20. 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. 

21. hat are the benefits of Blockchain that you know?
It encourages secure online transactions which is one of its biggest benefits. Being a distributed and decentralized ledger that keeps a close eye on all the transaction records, it doesn’t let the record to be altered by anyone. This enhances security. In addition to this, participants and business owners can always make sure of Los cost auditing at the end. One thing that can always be assured with blockchain is every block or unit can be transferred only once which simply eliminates the double-spending problem.

22. What challenges information leak can impose on an organization?
Information leaks can cut down the reputation of an organization up to an excellent extent. In addition to this, it can be the reason for an organization bearing huge losses. Many organizations that fail to implement security protocols to keep their data secure have already lost the trust of their customers and are struggling very hard to get the same reputation again. The overall profits of any organization can reduce up to 80% if no attention is paid to the online transaction security.

23. How you will handle the risk management when it comes to securing the transactions records?
It is a process of finding the threats and all the vulnerabilities to the financial records of an organization. The best thing that can be done against this approach is to take the right countermeasures against them immediately. Another approach is to pay attention to a back-up plan. Based on the value of information, more approaches such as buying new risk management software can simply be considered. The prime risk of information is from black-hat hackers.

24. How does Bitcoin use Blockchain?
A transaction is a transfer of value between Bitcoin wallets that gets included in the blockchain. Bitcoin wallets keep a secret piece of data called a private key or seed, which is used to sign transactions, providing a mathematical proof that they have come from the owner of the wallet.

25. Can you explain the elements of the Blockchain Ecosystem?

There square measure four completely different part of the Blockchain system

  • Shared Ledger
  • Virtual Machine
  • Node application
  • Consensus Algorithm

26. How can you easily see details about transactions and blocks?
Using blockchain explorers like or 

27. What does gas usage in a transaction depend on?

It depends on the amount of storage, and type and number of instructions (opt codes). Each EVM opt code has a fixed amount of gas.

28. What error will I get if I put multiple contract definitions into a single Solidity file?
It is perfectly fine to put multiple contract definitions into a single Solidity file.

29. What variables are stored in the Storage and Memory areas respectively?
State variables and local variables (which are references to the state variables) are stored in Storage. Function arguments are located in the Memory area.

30. What is a D App?
Decentralized applications (dApps) are applications that run on a P2P network of computers rather than a single computer. dApps have existed since the advent of P2P networks. They are a type of software program designed to exist on the Internet in a way that is not controlled by any single entity.

Decentralized applications don’t necessarily need to run on top of a blockchain network. BitTorrent, Popcorn Time, BitMessage, Tor, are all traditional dApps that run on a P2P network, but not on a Blockchain (which is a specific kind of P2P network).
As opposed to simple smart contracts, in the classic sense of Bitcoin, which sends money from A to B, dApps have an unlimited number of participants on all sides of the market. 

31. Give some examples of DApps?
Golem. The Golem project aims to create the first global market for idle computer power. Augur. Augur aims to combine the concept of prediction markets with the power of the decentralized network to create a forecasting tool, for potential trading gains. Aragon Network aims to act as a digital jurisdiction that is extremely convenient for everyone to operate on

32. How are transactions and blocks encrypted in the Bitcoin implementation?
Bitcoin blocks are not encrypted in any way: Every block is public. What prevents modifications and guarantees data integrity is a value called the block hash. Block content is processed using a special hash function—in the case of Bitcoin, it’s SHA256—and the resulting value is included in the blockchain.

33. What do you understand by the security of a block?
Every block in a Blockchain is secured by a strong cryptographic hash algorithm. Each block consists of a unique hash pointer. Any change in the block element will take to the change in the hash identifier of the block. Thus, it provides an optimum level of security. Hence once should not get worried about this protection because this security is a gift in an exceeding block. 

34. What happens if the execution of a Smart Contract costs more than the specified gas?
The user doesn’t get a refund and also the execution halts as soon as all the gas is used up and no changes are made to the contract.

35. What are the benefits of proof of stake as opposed to proof of work?
See A Proof of Stake Design Philosophy for a more long-form argument.

In short:

No need to consume large quantities of electricity in order to secure a blockchain (eg. it’s estimated that both Bitcoin and Ethereum burn over $1 million worth of electricity and hardware costs per day as part of their consensus mechanism).
Because of the lack of high electricity consumption, there is not as much need to issue as many new coins in order to motivate participants to keep participating in the network. It may theoretically even be possible to have negative net issuance, where a portion of transaction fees is “burned” and so the supply goes down over time.
Proof of stake opens the door to a wider array of techniques that use game-theoretic mechanism design in order to better discourage centralized cartels from forming and, if they do form, from acting in ways that are harmful to the network (eg. like selfish mining in proof of work).
Reduced centralization risks, as economies of scale, are much less of an issue. $10 million of coins will get you exactly 10 times higher returns than $1 million of coins, without any additional disproportionate gains because at the higher level you can afford better mass-production equipment.
Ability to use economic penalties to make various forms of 51% attacks vastly more expensive to carry out than proof of work – to paraphrase Vlad Zamfir, “it’s as though your ASIC farm burned down if you participated in a 51% attack”.

36. What is a hash on the Blockchain?
Signatures are a fundamental part of blockchains. Similar to signing a check, cryptographic signatures determine which transactions are valid. Signatures are generated from a hash of data to be signed, and a private key. Transaction hashes are highly visible in a blockchain.

37. What is the difference between the distributed database and the traditional database?
There are many differences between distributed database and traditional database, they are,

Operations in Distributed Database (Blockchain) and Traditional Database

Blockchain Distributed Database – In the blockchain, we can store data but there is no chance for edit and delete.

Traditional Database – In the traditional database, we can perform CRUD operations.

Replication in Blockchain Vs Traditional Database

Blockchain – There is a full replication of block on every peer of the blockchain.

Traditional – Here we can have master-slave multi-master.

The consensus in Blockchain Vs Traditional Database

Blockchain – In the blockchain, most of the peers agree on the outcome of transactions.

Traditional – Here in the traditional database, distributed transactions can happen.

38. What are the main blockchain features?

Blockchain has a lot of features. The main features are as below.

Security: Blockchain provides unparalleled security

Immutability: Data once are written cannot be changed or altered.

Fast: Blockchain offers quick transactions

Decentralized: Any centralized authority or entity do not control it

Fault-tolerant: Blockchain networks are fault-tolerant.

Low transaction fees: No need for the third party makes it cheaper and more effective

Minting: Provides coin minting by various methods.

39. Discuss the role of encryption in blockchain?
Encryption is an age-old technique to protect data from third parties or leaks. It is the basics of data security in the modern world. Blockchain also utilizes encryption to good effect. The data before it is sent off to the receiver is encrypted. The received will only be able to unlock it as it is only meant for him. Once the receiver receives it, it is unencrypted and can be used as a liked.

Blockchain also uses encryption in other ways. Also, modern blockchain solution tends to improve encryption and provide complete privacy-based experience for users.

40. Why is blockchain more trustworthy?
The blockchain is trustworthy because of many reasons. The first reason is the security that blockchain offers. It is the most secure technology solution right now. Next, it is entirely decentralized. This removes the need for a centralized entity and the risks associated with it.

41. What are the Merkle trees? Are they important?
Merkle trees are a data structure that is used in cryptography. It is also known as the hash tree. Technically, in the tree, every leaf node is designated with the hash of the data block. The non-leaf node on the other hand stores the cryptographic hash of the child nodes. Hash trees are incredibly efficient in terms of performance and can be used to verify large data structures.

For example, it is not required to transfer the whole block to verify a block.

Note: This is an advanced blockchain interview question.

42. What makes RSA a secure cryptographic algorithm?
RSA provides a state of the security algorithm for applications to use. It stands for Rivers, Shamir, and Adelman. They are the developer of this algorithm. RSA offers public-key encryption and hence is applicable in a variety of use-cases including blockchain. It is also the first encryption that is widely used for signing data and encryption. It works by using both private and public keys.

43. Explain the blind signature and how it is useful?
A blind signature is an essential part of cryptography where the information is blinded or encrypted. The information is signed and hence become encrypted. The approach is verified and ensure that privacy protocols are maintained in the network.

44. What are blocks in a blockchain ecosystem?
Blockchain stores transactional data in blocks that are linked together to form a chain. Hence the name ‘Blockchain’.

Each block contains the following.

1. A hash (a digital fingerprint or identifier) that uniquely identifies the block.

2. The hash of the previous block. This links the block to the previous block and hence forms the blockchain. It also prevents any block from being altered or a block being inserted between two existing blocks.

3. Transactions: Each block contains a batch of timestamped transactions.

45. In your opinion, how great is the opportunity for food businesses to make blockchain a central part of their digitalization strategy? What challenges need to be overcome for market-wide adoption?
There is demand among participants in the food industry for a trusted and end-to-end view of their supply chains. There is also a need to see the industry as a whole move toward greater transparency. Suppliers, processors, distributors, retailers, logistics providers, and consumers all benefit from the ability to trace their products across a holistic journey to ensure food safety and respond faster to contaminations.

With the IBM Food Trust solution, suppliers and retailers have the capability to quickly and efficiently trace and recall products. The solution provides participants with a permissioned, shared view of food industry information. With blockchain as a central part of the digitalization strategy, the food industry has the opportunity to respond quickly, effectively, and precisely to health risks.

Challenges to overcome for market-wide adoption include:
Getting the data onto the network.
Through working with our early adopters we’ve come a long way towards identifying what information needs to go on to the blockchain, in what formats, for what types of food products, etc. We are also working on making it even easier for any organization – a small farmer or producer to a large retailer – to get data onto the blockchain.

A solution for the industry must leverage existing standards in that industry.
Data must be exchanged between parties on a blockchain network using standard formats to ensure effective data sharing between partners. The IBM Food Trust solution uses GS1 standards, which is used by the industry so that companies can talk to each other in a language everyone understands.

46. What have you liked or what has surprised you about the technology?
The fabric has done a fantastic job combining distributed ledger technology in a way that can be used to meet the needs of businesses. The focus on security and privacy combined with modularity means that some of the hard questions that get asked now have answers.

47. What do you do, and what is your professional background?

I focus my time and resources on using technology to help humanity become more conscious, happy and prosperous.

I am a conscious technologist, a conscious capitalist, and a serial entrepreneur who has launched several startups in many sectors across the globe. As such, I have been honored with eleven different innovation awards that are a result of my purpose to create new ways for communities to become better versions of themselves, from a social and/or financial standpoint.

48. Why does blockchain technology excite you?
Up to date, the structure we have used for business, managing our communities, and so on, has been based on a linear and centralized approach which is very much dependent on a mental framework that is not viable anymore. As technology’s pace accelerates, as the challenges we face become more and more daunting, we have no other choice than to trust ourselves and our communities to collectively take the right decisions … together.

This is one of the reasons why blockchain is so amazing as it is very much aligned with these new ways of living. With the new era, we will experience for the next millennium or so; acquiring the properties of multi-faceted growth (compared to linear/revenue only growth) is important for both companies and communities.

49. What are your biggest hopes and fears regarding the future of this technology?
I believe that our future as a whole is based on the adoption of the blockchain. I believe it holds the keys to humanity’s next level of evolution. Obviously, it will entail many transformations at all level of our societies, the main one being that certitudes and tangibility will become fading concepts as the blockchain, together with its content, smart contracts, etc., will auto-adjust itself dynamically as a function of its environment, just like our DNA.

50. Name the two types of records that are present in the blockchain database?
These records are block records and transactional records. Both these records can easily be accessed and the best thing is it is possible to integrate them with each other without following the complex algorithms. 

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

These are:

  • Centralized Ledgers
  • Decentralized Ledgers
  • Distributed Ledgers

52. Name the 2 kinds of records that are present within the Blockchain Database?
These records are block records and transactional records. Each of these records will simply be accessed, and also the neatest thing is, it’s doable to integrate them with one another while not following the complicated algorithms.

53. State difference between proof of stake and proof of work?

Proof of Work

  • The possibility of Mining a Block depends upon the amount of work a miner does
  • Takes more energy than a proof of stake

Proof of Stake

  • Stakeholder Validate new block by but utilizing their share of coin on the network
  • The first example of proof of stake is Peercoin

54. What does gas usage in a transaction depend on?
It depends on the amount of storage, and type and number of instructions (opt codes). Each EVM opt code has a fixed amount of gas

55. Explain why a blockchain needs tokens to operate?
Coins/tokens are used to implement changes between states. When somebody does a transaction, this is a change of state, and coins are moved from one address to another. Apart from that, transactions can contain additional data, and a change of state is used to mutate data—the only way to do this in an immutable-by-definition blockchain. Technically, a blockchain doesn’t need coins for its essential operations, but without them, some other way needs to be introduced to manage states of the chain and to verify transactions.

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