Blockchain Technology Exam Paper 1

Here is the detailed solution for the Pune University CS-3511: Blockchain Technology exam paper.

Q1) Attempt any Eight of the following (out of Ten):

a) What is a hash function?

A hash function is a mathematical function that converts an input (or message) into a fixed-length string of characters, typically a hash value or digest. In blockchain, cryptographic hash functions (e.g., SHA-256) are used to ensure data integrity, security, and immutability.

b) Define PoW.

Proof of Work (PoW) is a consensus mechanism used in blockchain networks like Bitcoin. It requires participants (miners) to solve complex mathematical problems to validate transactions and add new blocks to the blockchain. PoW ensures network security but consumes significant computational power.

c) What is a DApp?

A Decentralized Application (DApp) is an application that runs on a blockchain or a peer-to-peer network instead of a centralized server. It operates on smart contracts and provides transparency, security, and censorship resistance.

d) What is consensus?

Consensus is the process through which blockchain participants agree on the validity of transactions and maintain a single version of truth. Popular consensus mechanisms include PoW, Proof of Stake (PoS), and Byzantine Fault Tolerance (BFT).

e) What is a Nonce?

A Nonce (Number Only Used Once) is a random number used in cryptographic operations. In PoW blockchains, miners generate a nonce to find a valid hash that meets the network’s difficulty target.

f) What is Ether?

Ether (ETH) is the native cryptocurrency of the Ethereum blockchain. It is used to pay for transaction fees, deploy smart contracts, and participate in network governance.

g) Give the names of cryptocurrencies where blockchain is used.

Some popular cryptocurrencies that use blockchain technology include:

Bitcoin (BTC)
Ethereum (ETH)
Ripple (XRP)
Litecoin (LTC)
Cardano (ADA)

h) What is DAO?

A Decentralized Autonomous Organization (DAO) is an organization that operates through smart contracts on a blockchain, eliminating centralized control. DAOs use governance tokens for decision-making and voting.

i) What is plain text and cipher text?

Plaintext refers to unencrypted, readable data.
Ciphertext is encrypted data that appears unreadable without decryption using a key.

j) What is a smart contract?

A smart contract is a self-executing program on a blockchain that runs when predefined conditions are met. It automates transactions, reducing the need for intermediaries.

Q2) Attempt any Four of the following (out of Five):

a) What are the advantages of smart contracts?

Automation: Executes agreements without intermediaries.
Security: Immutable and tamper-proof.
Transparency: Publicly verifiable on the blockchain.
Efficiency: Faster execution compared to traditional contracts.

b) What is hard fork and soft fork?

Hard Fork: A permanent split in the blockchain that creates two separate chains, leading to backward incompatibility (e.g., Bitcoin and Bitcoin Cash).
Soft Fork: A backward-compatible upgrade that allows old nodes to recognize new blocks as valid (e.g., SegWit in Bitcoin).

c) What is PoS? Which blockchain uses PoS?

Proof of Stake (PoS) is a consensus mechanism where validators are chosen based on the number of tokens they hold and stake.
Ethereum 2.0, Cardano, and Solana use PoS to secure their networks.

d) Explain symmetric & asymmetric key cryptography.

Symmetric Key Cryptography: Uses a single key for encryption and decryption (e.g., AES).
Asymmetric Key Cryptography: Uses a public-private key pair (e.g., RSA, ECC) for secure communication.

e) Explain the structure of blocks in blockchain.

Each block in a blockchain contains:

Block Header (Hash, Previous Block Hash, Nonce, Timestamp)
Transaction List
Merkle Root (Hash of all transactions)

Q3) Attempt any Two of the following (out of Three):

a) What are the different types of Blockchain?

Public Blockchain: Open to all (e.g., Bitcoin, Ethereum).
Private Blockchain: Restricted access (e.g., Hyperledger).
Consortium Blockchain: Controlled by multiple organizations.
Hybrid Blockchain: Combines public and private blockchain features.

b) What are the challenges of Blockchain?

Scalability Issues
High Energy Consumption (PoW)
Regulatory and Legal Concerns
Lack of Awareness and Adoption

c) Write a short note on ICO.

An Initial Coin Offering (ICO) is a fundraising method where new blockchain projects issue tokens in exchange for cryptocurrencies like Bitcoin or Ether. It is similar to an IPO but for crypto projects.

Q4) Attempt any Two of the following (out of Three):

a) Write a short note on digital signature.

A digital signature is a cryptographic method used to verify the authenticity and integrity of digital messages or documents. It uses public-key cryptography to ensure that data has not been tampered with.

b) Explain the working of mining.

Mining is the process of validating transactions and adding them to a blockchain. Miners compete to solve cryptographic puzzles (PoW), and the first to find a valid hash gets rewarded.

c) Write a short note on Byzantine Fault Tolerance (BFT).

BFT is the ability of a blockchain network to function correctly even if some nodes act maliciously. It ensures that consensus is achieved despite faulty or adversarial nodes.

Q5) Attempt any One of the following (out of Two):

a) Which are the different data types in Solidity?

Solidity supports various data types, including:

Boolean (true or false)
Integer (uint, int)
Address (Ethereum address)
String and Bytes
Array (Fixed and dynamic)
Mapping (Key-value pairs)

b) Differentiate between Blockchain and Database.

Feature	Blockchain	Traditional Database
Structure	Distributed ledger	Centralized storage
Control	Decentralized	Controlled by an entity
Security	Highly secure with cryptographic hashing	Vulnerable to central point attacks
Modification	Immutable	Can be modified or deleted
Transparency	Public verification	Access-controlled

This is a detailed solution for your Blockchain Technology exam paper. Let me know if you need any explanations or modifications.