I’ll solve the first paper in detail. If you need solutions for the others, let me know.
Solution for Blockchain Technology (CS-3511) Exam Paper
Q1) Attempt any Eight of the following (out of Ten):
(8 × 1 = 8)
(a) What is a hash function?
A hash function is a cryptographic function that converts input data into a fixed-length string (hash value). It is a one-way function, meaning it cannot be reversed. Hash functions ensure data integrity and security in blockchain technology. Example: SHA-256 in Bitcoin.
(b) Define PoW.
Proof of Work (PoW) is a consensus mechanism used in blockchain networks, where miners solve complex mathematical puzzles to validate transactions and create new blocks. It ensures network security by making attacks computationally expensive.
(c) What is a DApp?
A Decentralized Application (DApp) is a software application that runs on a blockchain instead of a centralized server. It operates autonomously, uses smart contracts, and is open-source.
(d) What is consensus?
Consensus is the process used by blockchain networks to agree on the validity of transactions and blocks. Common consensus mechanisms include Proof of Work (PoW) and Proof of Stake (PoS).
(e) What is a nonce?
A nonce (number used once) is a random or sequential number added to a block header in PoW mining. Miners adjust the nonce to find a valid hash that meets the required difficulty level.
(f) What is Ether?
Ether (ETH) is the native cryptocurrency of the Ethereum blockchain. It is used to pay for transaction fees and computational services on the Ethereum network.
(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 governed by smart contracts on a blockchain, without centralized control. Decisions are made through voting by token holders.
(i) What is plain text and cipher text?
- Plain Text: Readable data before encryption.
- Cipher Text: Encrypted data that is unreadable without a decryption key.
(j) What is a smart contract?
A smart contract is a self-executing contract with predefined rules written in code. It automatically enforces agreements without intermediaries when conditions are met.
Q2) Attempt any Four of the following (out of Five):
(4 × 2 = 8)
(a) What are the advantages of smart contracts?
- Automation: Transactions execute automatically without intermediaries.
- Security: Uses cryptographic techniques, reducing fraud risks.
- Transparency: All contract details are visible on the blockchain.
- Cost Savings: Eliminates the need for third parties like banks or lawyers.
- Speed: Transactions are completed faster than traditional processes.
(b) What is a hard fork and soft fork?
- Hard Fork: A permanent change to the blockchain protocol that is not backward-compatible (e.g., Bitcoin Cash fork from Bitcoin).
- Soft Fork: A protocol upgrade that is backward-compatible, allowing old nodes to accept new rules (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 coins they hold and stake. It is energy-efficient compared to PoW.
Examples of blockchains using PoS: Ethereum 2.0, Cardano, Solana, Polkadot.
(d) Explain symmetric & asymmetric key cryptography.
- Symmetric Key Cryptography: Uses the same key for encryption and decryption (e.g., AES, DES).
- Asymmetric Key Cryptography: Uses a public key for encryption and a private key for decryption (e.g., RSA, ECC). It is commonly used in blockchain transactions.
(e) Explain the structure of blocks in Blockchain.
A blockchain block consists of:
- Block Header: Contains metadata like block number, timestamp, previous block hash, and nonce.
- Transaction List: Stores validated transactions.
- Merkle Root: A cryptographic summary of all transactions in the block.
- Hash Pointer: Links the block to the previous block, forming a chain.
Q3) Attempt any Two of the following (out of Three):
(2 × 4 = 8)
(a) What are the different types of Blockchain?
- Public Blockchain: Open to everyone (e.g., Bitcoin, Ethereum).
- Private Blockchain: Restricted access, controlled by an organization (e.g., Hyperledger Fabric).
- Consortium Blockchain: Shared control by multiple organizations (e.g., R3 Corda).
- Hybrid Blockchain: A combination of public and private blockchain features.
(b) What are the challenges of Blockchain?
- Scalability: Limited transaction processing speed.
- Energy Consumption: High energy use in PoW blockchains.
- Regulatory Issues: Lack of clear legal frameworks.
- Security Risks: Smart contract vulnerabilities.
- Interoperability: Difficulty in connecting different blockchains.
(c) Write a short note on ICO.
An Initial Coin Offering (ICO) is a fundraising method where new cryptocurrency tokens are sold to investors. It helps startups raise capital for blockchain projects.
Q4) Attempt any Two of the following (out of Three):
(2 × 4 = 8)
(a) Write a short note on digital signature.
A digital signature is a cryptographic technique used to verify the authenticity of a message or transaction. It ensures integrity, authenticity, and non-repudiation using public-key cryptography.
(b) Explain the working of mining.
- Transaction Collection: Miners collect pending transactions.
- Hash Calculation: Miners solve a cryptographic puzzle by finding a valid nonce.
- Block Validation: Once a valid hash is found, the block is added to the blockchain.
- Reward Distribution: Miners receive rewards (e.g., Bitcoin mining rewards).
(c) Write a short note on Byzantine fault tolerance.
Byzantine Fault Tolerance (BFT) ensures a distributed system can function correctly even if some nodes act maliciously. Examples include Practical Byzantine Fault Tolerance (PBFT) used in Hyperledger Fabric.
Q5) Attempt any One of the following (out of Two):
(1 × 3 = 3)
(a) Which are the different data types in Solidity?
Solidity supports various data types:
- Boolean: True or False.
- Integer: Signed and unsigned integers (uint256, int256).
- Address: Ethereum address type.
- String: Stores text data.
- Array: Fixed or dynamic collection of elements.
- Struct: User-defined data structure.
- Mapping: Key-value storage.
(b) Differentiate between Blockchain and Database.
| Feature | Blockchain | Database |
|---|---|---|
| Structure | Distributed Ledger | Centralized storage |
| Security | Cryptographic hashing | Authentication & authorization |
| Control | Decentralized | Centralized |
| Modification | Immutable | Can be modified |
| Use Cases | Cryptocurrency, Smart Contracts | Banking, E-commerce |
This completes the detailed solutions. Let me know if you need further explanations or additional answers!