Blockchain:PYQ's

- Who published a white paper proposing Ethereum in 2013?
Ethereum was proposed by Vitalik Buterin. He published the white paper in late 2013.

- What is EVM?
EVM is the runtime environment for smart contracts in Ethereum.

-What happens if someone loses the private key of his wallet?
If someone loses the private key of their wallet, they lose access to the associated funds permanently. Recovery is usually impossible, emphasizing the importance of securely storing and backing up private keys.

- Which institute standardized AES algorithm?
The Advanced Encryption Standard (AES) algorithm was standardized by the National Institute of Standards and Technology (NIST).

 -What is Nonce?
In blockchain, a nonce is a number that is used only once. It is often employed in the mining process to vary the output of hash functions.

- What is Non-repudiation?
Non-repudiation refers to the assurance that a party involved in a communication cannot deny the authenticity or origin of a message or transaction.

- What is ICO?
ICO is a fundraising method in which new cryptocurrency projects sell their underlying crypto tokens to early investors. It is a way to raise capital for a new blockchain-based project.

 -Who owns the Blockchain?
No single entity owns the entire blockchain. It is a decentralized and distributed ledger maintained by a network of nodes.

 -What is Gas & Gas limit?
Gas is the unit used to measure the computational effort required to execute operations or contracts on the Ethereum network. Gas limit is the maximum amount of gas a user is willing to pay for a transaction or contract execution.

-What are the advantages of smart contract? Explain any four.

Advantages of Smart Contracts:

Trust: Smart contracts execute automatically based on predefined rules, eliminating the need for trust in a third party. The decentralized and transparent nature of blockchain builds trust.

Efficiency: Automation reduces the time and costs associated with traditional contract execution, as there's no need for intermediaries or manual verification.

Accuracy: Since smart contracts operate on code, the execution is precise, minimizing errors and misunderstandings that can arise in traditional contracts.

Security: Smart contracts are secured by blockchain's cryptographic features. Once deployed, they cannot be altered, providing a high level of security.

- What are the layers of blockchain?

Network Layer: Manages network communication, peer discovery, and data synchronization among nodes.

Consensus Layer: Determines how nodes agree on the state of the blockchain. It includes algorithms like Proof-of-Work (PoW) or Proof-of-Stake (PoS).

Smart Contract Layer: Facilitates the creation, execution, and enforcement of smart contracts. Ethereum is a prominent example with its EVM (Ethereum Virtual Machine).

Application Layer: Houses decentralized applications (DApps) that utilize the underlying blockchain infrastructure.

-What is the formula to calculate transaction fee in Etheream?

Transaction Fee = Gas Used (units) * Gas Price (wei per unit)

Gas represents computational effort, and the fee is calculated based on the amount of gas consumed and the gas price set by the user.

-What is plain text and cipher text?

Plain Text: The original, readable data before any encryption is applied.

Cipher Text: The encrypted data that results from applying an encryption algorithm to the plain text. It appears as random and unreadable without the decryption key.

- What is FPGA?

FPGA is a hardware device with reconfigurable logic gates and circuits.

Unlike ASICs, FPGAs can be programmed and reprogrammed, making them versatile for different applications, including cryptocurrency mining.

 -What is smart contract?

A self-executing contract with the terms directly written into code.

Smart contracts automatically enforce and execute the terms when predefined conditions are met, without the need for intermediaries.

-What is the size of encryption key in DES?
DES (Data Encryption Standard) uses a 56-bit key. The key length influences the security of the encryption.

 What is ASIC?

ASIC is a hardware designed for a specific task or application, such as cryptocurrency mining.

It offers high performance for a specific function but lacks flexibility compared to general-purpose processors.

- Which algorithm is used by Bitcoin to verify transactions?
Bitcoin uses the SHA-256 hashing algorithm to verify transactions. Miners must find a nonce that, when hashed with the transaction data, produces a hash with a specific pattern.

- Which is a unique PoS cryptocurrency that is aimed at delivering ateroperability among other blockchains

Unique PoS Cryptocurrency for Interoperability:

Cardano (ADA) is known for its Proof-of-Stake consensus algorithm and focuses on providing interoperability and scalability in the blockchain space.

What is DAPP?

A DApp operates on a decentralized network and is built on blockchain technology.

DApps use smart contracts to automate processes, ensuring transparency and security.

-What is the difference between public and private blockchains?

Public Blockchain: Open to anyone, decentralized, and transparent (e.g., Bitcoin, Ethereum).

Private Blockchain: Restricted access, often controlled by a single entity for specific purposes like business applications.

-What is P2P сrypto Exchange?

A Peer-to-Peer (P2P) crypto exchange allows users to trade directly with each other without intermediaries.

It provides more control and ownership over assets compared to centralized exchanges.

Whis is 'BFT?

BFT (Byzantine Fault Tolerance):

BFT is a consensus algorithm that ensures the integrity of a distributed system, even when some nodes fail or act maliciously.

It's crucial for maintaining the reliability and security of blockchain networks.

-What is Hybrid Blockchain?

Combines features of both public and private blockchains.

Offers flexibility, allowing certain data to be private while utilizing the security and transparency of a public blockchain.

-Write a short note on life cycle of smart contract 

Creation: Developers write the code for the smart contract.

Execution: The smart contract is deployed on the blockchain and operates based on predefined conditions.

Termination: The smart contract completes its tasks, and outcomes are recorded on the blockchain.

-What is HArd & Soft forks?

Hard Fork: Involves a fundamental change that is not backward-compatible. All nodes must upgrade to continue participating.

Soft Fork: Involves a backward-compatible change, allowing non-upgraded nodes to still participate in the network.

-What is POW?

POW (Proof-of-Work):

POW is a consensus algorithm where participants (miners) solve complex mathematical problems to validate transactions and create new blocks.

It's resource-intensive and helps secure the network against attacks.

-Write a short note on challenges of blockchain

Challenges of Blockchain:

Challenges include scalability issues, interoperability concerns between different blockchains, regulatory uncertainties, and the environmental impact of energy-intensive consensus mechanisms like PoW.

 -Write a short note on ICO?

ICO (Initial Coin Offering):

ICO is a fundraising method where new cryptocurrency tokens are sold to investors before being listed on exchanges.

It allows projects to raise capital by selling a portion of their cryptocurrency.

-Which are the different value data types in solidity?

Solidity, the programming language for Ethereum smart contracts, includes data types like uint (unsigned integer), int (signed integer), address, bool, string, and more.

- Describe EVM with the help of neat diagram.

Stream Cipher and Block Cipher:

Stream Cipher: Operates on individual bits or bytes of data, encrypting or decrypting one at a time. It is often used for real-time communication and is more efficient for streaming data.

Block Cipher: Operates on fixed-size blocks of data, encrypting or decrypting the entire block at once. It is commonly used for securing stored data and messages.

 -Define transaction and explain its structure.

- What are the uses of SHA algorithm?

The Secure Hash Algorithm (SHA) family of cryptographic hash functions, designed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST), has several important uses:

Data Integrity: SHA algorithms generate fixed-size hash values (digests) that uniquely represent input data. By comparing hash values, one can verify the integrity of the original data. Any change to the data will result in a different hash value.

Digital Signatures: SHA is commonly used in combination with asymmetric encryption algorithms to create digital signatures. These signatures provide authentication and verify the origin and integrity of digital messages.

Password Hashing: SHA algorithms are employed to securely hash passwords. Storing hashed passwords instead of plaintext enhances security, as it makes it more challenging for attackers to reverse-engineer passwords.

Blockchain Technology: In blockchain, SHA algorithms are used to create cryptographic hashes for blocks and transactions. For example, Bitcoin's PoW consensus relies on SHA-256 to generate a hash that meets specific criteria, contributing to the security of the network.

 -What is Public & Private blockchain?

Public Blockchain:

Accessibility: Open to anyone; anyone can join the network, participate in transactions, and validate blocks.

Decentralization: Multiple nodes (computers) maintain the network, and no single entity controls it.

Transparency: All transactions are visible to all participants, enhancing transparency and accountability.

Examples: Bitcoin and Ethereum are examples of public blockchains.

Private Blockchain:

Accessibility: Restricted to a specific group of participants, usually within a single organization or consortium.

Decentralization: Controlled by a centralized entity or a limited number of nodes.

Privacy: Access to data and transactions is restricted, providing privacy among participants.

Examples: Hyperledger Fabric and R3 Corda are examples of private blockchains.

- Write a short note on crypto wallet.

A crypto wallet is a digital tool that allows users to securely store and manage their cryptocurrency assets.

It consists of a public key (for receiving funds) and a private key (for authorizing transactions).

Wallets can be software-based (online, desktop, or mobile) or hardware-based (physical devices).

Wallets enable users to send, receive, and monitor their cryptocurrency balances.

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 -What are the tasks of miners?

Tasks of Miners:

Transaction Verification: Miners verify transactions by solving complex mathematical problems using computational power.

Block Creation: Verified transactions are grouped into blocks, and miners compete to solve the proof-of-work problem to create a new block.

Consensus: Miners participate in the consensus mechanism (e.g., Proof-of-Work) to agree on the state of the blockchain.

Incentive: Miners are rewarded with newly created cryptocurrency and transaction fees for their efforts.

 -Which are the components of blockchain?

Blocks: Containers for transaction data and other information.

Transactions: Records of data exchanges between participants.

Chain: The linkage of blocks through cryptographic hashes, forming a secure and chronological sequence.

Consensus Mechanism: Rules or algorithms that facilitate agreement on the state of the blockchain.

Decentralized Network: Nodes that maintain copies of the entire blockchain, ensuring redundancy and security.

- Write a short note on DES.

DES (Data Encryption Standard):

DES is a symmetric-key block cipher used for encryption and decryption of electronic data.

Developed by IBM in the 1970s, it became a widely adopted encryption standard.

DES uses a 56-bit key, and its 64-bit block size encrypts data in 64-bit chunks.

Over time, DES became vulnerable to brute-force attacks due to its small key size, leading to the development of more secure encryption algorithms.