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 Non-repudiation?
Non-repudiation is a security property that ensures a party in a communication cannot deny having sent or received a message. In blockchain, digital signatures and cryptographic hashing ensure transaction authenticity and prevent tampering.
b) What is difficulty in a block?
Block difficulty refers to the level of computational effort required to mine a new block in a blockchain. It is dynamically adjusted in Proof of Work (PoW) systems like Bitcoin to maintain a consistent block generation time.
c) In which network, each & every node itself is a client and server?
A peer-to-peer (P2P) network is where each node acts as both a client and a server. This decentralized structure is used in blockchain technology to ensure trustless and distributed consensus.
d) What is Ether?
Ether (ETH) is the native cryptocurrency of the Ethereum blockchain. It is used for transaction fees, executing smart contracts, and participating in Ethereum’s governance.
e) What is consensus?
Consensus is the mechanism through which blockchain participants agree on the validity of transactions and maintain a single version of truth. Examples include Proof of Work (PoW) and Proof of Stake (PoS).
f) What is a full node?
A full node is a computer that fully validates and stores the blockchain ledger. It maintains the entire blockchain history, verifies transactions, and helps secure the network.
g) What is Remix?
Remix is an open-source web-based IDE for writing, testing, and deploying Solidity smart contracts on Ethereum. It provides debugging tools and real-time code execution.
h) What is an immutable ledger?
An immutable ledger is a database that cannot be altered or deleted. In blockchain, once a transaction is recorded, it becomes permanent and tamper-proof due to cryptographic hashing.
i) Define genesis block.
The genesis block is the first block in a blockchain. It serves as the foundation of the chain and has no previous block reference. For example, Bitcoin’s genesis block was mined by Satoshi Nakamoto in 2009.
j) What is EVM?
The Ethereum Virtual Machine (EVM) is a decentralized runtime environment for executing smart contracts on the Ethereum blockchain. It enables developers to deploy decentralized applications (DApps) securely.
Q2) Attempt any FOUR of the following (out of FIVE):
a) Define Symmetric and Asymmetric Key Cryptography.
- Symmetric Key Cryptography: Uses a single key for both encryption and decryption (e.g., AES, DES).
- Asymmetric Key Cryptography: Uses a pair of keys (public and private) for encryption and decryption (e.g., RSA, ECC).
b) What is a stream cipher & block cipher?
- Stream Cipher: Encrypts data bit by bit (e.g., RC4).
- Block Cipher: Encrypts fixed-size blocks of data (e.g., AES, DES).
c) List the applications of hash function.
- Data integrity verification
- Digital signatures
- Password hashing
- Proof of Work in mining
- Merkle trees in blockchain
d) What is Gas and Gas Limit?
- Gas: The unit of computational work needed to execute transactions on Ethereum.
- Gas Limit: The maximum amount of gas a user is willing to spend for a transaction.
e) What is the purpose of a test network? List Ethereum testnets.
Test networks (testnets) allow developers to test smart contracts without using real cryptocurrency. Ethereum testnets:
- Ropsten
- Rinkeby
- Goerli
- Sepolia
Q3) Attempt any TWO of the following (out of THREE):
a) Compare client-server & peer-to-peer architecture.
| Feature | Client-Server | Peer-to-Peer (P2P) |
|---|---|---|
| Structure | Centralized | Decentralized |
| Control | Controlled by a single entity | No central authority |
| Security | Prone to single points of failure | More secure and resilient |
| Examples | Web applications | Blockchain, Torrent networks |
b) Explain the contents of a block of a blockchain.
A blockchain block contains:
- Block Header (Previous Block Hash, Merkle Root, Nonce, Timestamp)
- Transactions (A list of valid transactions)
- Merkle Root (Hash of all transactions)
c) Explain Ethereum architecture with a neat diagram.
Ethereum architecture consists of:
- Ethereum Virtual Machine (EVM)
- Smart Contracts
- Decentralized Applications (DApps)
- Consensus Mechanism (PoW → PoS in Ethereum 2.0)
Q4) Attempt any TWO of the following (out of THREE):
a) Enumerate and explain 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 features.
b) 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.
c) Explain forking with types.
- Hard Fork: Permanent split creating two separate blockchains (e.g., Bitcoin Cash).
- Soft Fork: A backward-compatible upgrade where old nodes still accept new transactions (e.g., SegWit in Bitcoin).
Q5) Attempt any ONE of the following (out of TWO):
a) Explain the uses of the SHA-256 algorithm.
SHA-256 (Secure Hash Algorithm 256-bit) is used for:
- Mining in Bitcoin
- Digital signatures
- Password security
- Data integrity checks
b) What are the tasks of miners?
Miners perform the following tasks:
- Transaction validation
- Solving cryptographic puzzles (PoW)
- Adding new blocks to the blockchain
- Ensuring network security
- Earning block rewards and transaction fees
This is a detailed solution for your Blockchain Technology exam paper. Let me know if you need further explanations!