You must heard of Blockchain technology. Blockchain is basically a technology that underpins digital currency (Bitcoin, Litecoin, Ethereum, and the like). So wanting to become a Blockchain expert, checkout these interview questions.

Q.1 What are blocks in the blockchain technology?
Blockchain primarily gives information about all the financial transactions. We can define block as a list of records, such that when these lists are combined with each other, they are referred as blockchain. For instance an organization has 50 ledger books such that the combination of which is referred as Blockchain and a single ledger would be referred as a block.
Q.2 Can we remove one or more block from the networks, in a Blockchain?
Yes, we can remove one or more block from the networks, in a Blockchain. At times only a specific portion of this online ledger is required to be considered. Therefore with the help of default options and filters, this can done without a lot of efforts.
Q.3 What is your understanding of Blockchain?
Blockchain is a technology that was initially designed for the Bitcoin which later got a lot of appreciation and acceptance due to an array of benefits it brings when it comes to monitoring and recording all the financial transactions made on a network. Blockchain is considered as a trusted methodology being used by a lot of organizations at present since everything is secure, and since it is an open source approach, it can be trusted for long run.
Q.4 How are blocks recognized in the Blockchain approach?
Every block in the online ledger 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.
Q.5 What is security of a block?
As we all may know that a block cannot be modified by all the users on a network. Due to which it offers an excellent level of security. Additionally every block is secured using cryptography that is another vote in this matter. Therefore one needs not to worry about the safety as well as the security of data present in a block.
Q.6 What are the network specific conditions required for using Blockchain technology in an organization?
There are pre-defined condition for using blockchain technology in an organization. However, the network must be a peer-to-peer network under the concerned protocols. This helps to validate the new block easily and also helps organizations to keep pace in this matter without investing further in third-party applications.
Q.7 How can we possibly modify data once it is written in a block?
It is not possible to modify data once it is written in a block. Such that if in case any modification is required, then the organization need to erase the information from all other blocks as well. Due to this reason data must be entered very carefully while using this approach.
Q.8 What kind of records are maintained in Blockchain?
At present there is no restriction on keeping any kind of records in the Blockchain approach. At present a lot of organizations across the world are using the Blockchain approach with records of medical transactions, events related to organizations, management activities, transaction processing, identity management, together with any generic type of records as well. Also remember record keeping is not just limited to these applications only.
Q.9 List the different types of blockchain technology/ledger.
As we may all know Bitcoin is one of the public blockchain which is truly decentralized in nature. The other kind of blockchain/ledger are -
1. Public blockchain
2. Private blockchain
3. Consortium or Federated blockchain
Q.10 What do you understand by public blockchain?
Public blockchain is public in nature which is completely decentralized such that anyone can read, write and join. In public blockchain no central authority controls the blockchain. The data can be validated as data once are written cannot be altered. Some examples of public blockchains are - Bitcoin and Ethereum.
Q.11 What do you understand by Secret Sharing?
We all know that security id one of the biggest concern in digital transactions. The Secret sharing approach is used for the same. Secret Sharing in Blockchain technology is an approach which divides secret or personal information into different units and then sends them to the users on the network. Such that the original information can only be shared when a participant to whom a share of the secret is allocated asks to combine them together with others.
Q.12 List the steps involved in the implementation of Blockchain project?
The process of implementing Blockchain Project involves the following steps -
1. Requirement identification
2. Screen ideas consideration
3. Project development for Blockchain
4. Feasible study on the security
5. Implementation
6. Controlling and monitoring the project
Q.13 What according to you are the benefits of Blockchain technology?
The benefits of blockchain include -
1. Blockchain encourages secure online transactions which is one of its biggest benefits.
2. Blockchain Technology does not permit alteration of records since it a distributed and decentralized ledger that keeps a close eye on all the transaction records . This enhances security.
3. Additionally participants and the business owners can always ensure of IOS cost auditing at the end.
Every block or unit can be transferred only once which eliminates the double spending problem.
Q.14 What are the types of records present in the blockchain database?
Blockchain Database has two types of records namely - Block records and Transactional records. Such that both these records can easily be accessed and it is possible to integrate them together without following complex algorithms.
Q.15 List the important principles in Blockchain which are used in eliminating the security threats that are required to be followed?
Some of the principles that are required to be followed with reference to time are -
1. Auditing
2. Securing applications
3. Securing testing and similar approaches
4. Database security
5. Continuity planning
6. Digital workforce training

All these principles are helpful in making the transactions records useful.
Q.16 What do you understand by security policy?
Security policy in blockchain describes what exactly is required to be secured on a system. Security policy bounds a network user under some core protocols which all must agree and follow to enhance the overall security. Therefore when it comes to information or financial records of an organization, multiple security policies are implemented.
Q.17 How can we handle risk management in order to secure the transactions records?
Risk management is a process of locating the threats and all the vulnerabilities to the financial records of an organization. One of the best approach is to take the right counter measures against them immediately. Second approach is to pay attention to a back-up plan. Therefore depending on the value of information, more approaches such as buying new risk management software can simply be considered. The prime risk to information is from black-hat hackers.
Q.18 What are the common type of ledgers which are considered by users in Blockchain?
common type of ledgers which are considered by users in Blockchain are -

1. Centralized Ledgers
2. Decentralized Ledgers
3 .Distributed Ledgers
Q.19 What are the points of difference between a blockchain ledger and an ordinary one?
Some of the point of differences are -
1. Prime difference is Blockchain is that it is a digital ledger that can be decentralized very easily which cannot be done in an ordinary ledger.
2. Chances of error in this approach are far less than that in an ordinary ledger.
3. In an ordinary ledger everything is prepared with hands or with human efforts while the Blockchain performs all its tasks automatically. It only required to be configured in a proper manner and by following all the guidelines.
Q.20 Why is blockchain considered a trusted approach?
Some of the reasons to consider Blockchain as a trusted approach are -
1. Its compatibility with other business applications due to its open-source nature.
2. Since all the transactions happen online, the developers have paid special attention to keeping up the pace when it comes to its security.
3. The type of business really doesn’t matter and the type of business someone owns, Blockchain can easily be considered.
Q.21 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.
Q.22 What are blocks in blockchain technology?
A block is part of the bitcoin network. A Block stores the Transactional data permanently. Also, the blocks are always sequential, and new data is added to the latest block. In simple words, it is a record book with a fixed size to it. Once a block is completed, a new block is generated which is then attached to the chain of blocks. This is where the name of “block” chain came from. All the information in the block is encrypted and can only be accessed by the receiver and sender.
Q.23 How blocks are created?
when the block size is reached the Blockchain automatically creates Blocks. As the block is a file, the transactions are kept on the file until it becomes full. They are listed linearly and are connected so that the latest block stays in contact of the previous one. To identify a block, using a mathematical function, a hash value is generated. It also indicates any changes that are made to a block.
Q.24 How are blocks changed together?
A hash value assigned to a block is used to chain them together. If the hash value is changed, this indicates that someone is trying to spoof the data stored in the hash. The blocks are linked by storing the hash value of the previous block.
'For instance:, block 3 will store the hash value of block 2 and so on.'
Q.25 Can blocks be removed from a blockchain?
The removal of blocks from a blockchain entirely based on how it is handled. Though it is not possible to manually remove a block. Nevertheless, if it is lost, then the blockchain generally tries to rebuild the database using other peers. While, once they are verified, to lower the blockchain size they can be deleted as it is not required anyone to do normal operations. It can be re-downloaded again when needed. This process is known as pruning.
Q.26 Can the data stored in a block modified once it is written? If so, why?
The data kept on the blockchain is protected with correct encoding employing a digital signature. This makes the data written in a block as a one-time process only. It cannot be altered by any means.
Q.27 What type of records can be stored in a blockchain?
As the Blockchain acts as a data structure which indicates that it can be used to store any form of data. Industries can make proper use of blockchain record types as they can completely take advantage of what it has to offer. The most common styles of records/data which will be unbroken in blockchain are:
Identity management
Transaction processing
Medical records
Management activities
Business transactions
Q.28 What is block identifiers?
On a blockchain every block has a unique identifier is. It is the hash value that acts as a unique identifier. This means that no two blocks identifiers will be identical.
Q.29 What do you understand by ICO?
ICO stands for Initial Coin Offering. It is similar in concept with an IPO(Initial Public Offering). ICO is used by start-ups or companies to raise capital for their product. It can be a direct blockchain product or a product utilizing benefits of the blockchain. To raise the money they sell their platform or service tokens.
Q.30 Is there a need to understand ICO in order to get a complete picture of blockchain technology?
ICO is one of the imperative parts of the blockchain ecosystem. This doesn’t mean that you need to learn about ICO and how they are implemented. But, it is always good to possess an understanding of ICO in the current market. ICO is one of the best use-cases of blockchain technology.
Q.31 Name the Popular platforms for developing blockchain applications?
The most popular platforms for developing blockchain applications include Ripple, R3 Cords, Hyperledger Fabric, Ethereum, and Quoru.
Q.32 What is Hyperledger?
Hyperledger is an open source collaborative effort to improve blockchain. It offers an enterprise-grade framework. These tools will help to strengthen blockchain implementation across multiple sectors including manufacturing, supply chains, finance, etc. The Linux Foundation manages it.
Q.33 What is a smart contract?
A smart contract is best defined as a computer code that lets you enforce rules and regulations between two parties that are going to interact to carry out a deal. The agreement once is written can be executed automatically for any number of times. Smart contracts is a legal agreement that is written with the help of code. It is widely used in blockchain to automate tasks and also bring transparency to a particular system. For example, smart contracts can be used to sell or own real-world assets.
Q.34 What is dApp?
dApp also stands for “decentralized application” that runs on a blockchain. Smart contracts are used to automate different functionality of the dApp. As it is an application, more than one peer can participate and is not controlled by a single entity. dApps generally follow a protocol or algorithm and also require an incentive attached to its functionality. Lastly, it is a completely open source.
Q.35 How is dApp different from an app?
dApps run on a decentralized network or system whereas apps, in general, are not designed to work in a decentralized ecosystem. dApps are the next generation apps that take advantage of blockchain and runs on it. NEO and Ethereum are included in the Popular blockchain solutions that support dApps.
Q.36 How are dApp different from a smart contract?
dApps are the decentralized app that fulfills a particular action or feature on the blockchain. It is maintained by an organization so that they can effectively automate some or complete processes. Smart contracts, on the other hand, are made to act as two peers under pre-defined rules using code. Unlike smart contracts, dApps can be accessed by multiple peers at any given time.
Q.37 What is Solidity?
Solidity is a high-level programming language that offers contract-based programming. It is used to enhance the functionality of Ethereum Virtual Machine and is also actively used to program Ethereum smart contracts. It is similar to JavaScript when it comes to syntax and esy to access.
Q.38 What is Metamask?
Metamask is a web app that lets you connect with Ethereum dApps directly from your browser. This means that you don’t need to have a full Ethereum node to access dApps and its functionalities.
Q.39 What is the lightning network?
To improve the working of bitcoin the lightning network is an off-chain and scalable solution. It will bring instant transactions at low or no cost associated with it. Moreover, it will make bitcoin more scalable by taking the majority of the hard work off-chain. The lightning network is in active development and is already being used by many vendors.
Q.40 What is atomic swap?
Atomic swap enables faster transfers thanks to the use of smart contracts. It is a revolutionary technology that allows peers to exchange one cryptocurrency to another without any intermediary exchange. It is done off-chain and between two different blockchains.
Q.41 What is a private key?
A private key is an alphanumeric phrase that is used in pair with a public key to provide encryption and decryption. It is a part of cryptographic algorithms that are used in blockchain security. The key is assigned to the key generator and should stay with him only. If he fails to do so, anyone can access the details or data located within the wallet or the address for which the private key is assigned.
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