Competitive Exam Master Guide — Cybersecurity & Technology
Blockchain Technology
Complete Study Resource
Covers all exam-relevant concepts — How blockchain works, Consensus Mechanisms, Types, Smart Contracts, CBDC, Digital Rupee, Indian initiatives & 65+ Interactive MCQs for Banking, UPSC, SSC, Railways & all Govt Exams
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Blockchain Technology Explained – Competitive Exam Guide
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📋 Table of Contents
- What is Blockchain? — Simple Definition
- Key Features of Blockchain
- How a Blockchain Works — Structure of Blocks
- Types of Blockchain — Public, Private, Consortium, Hybrid
- Consensus Mechanisms — PoW, PoS, PoA & More
- Smart Contracts — Definition & Uses
- Cryptocurrency — Bitcoin, Ethereum & Altcoins
- CBDC & Digital Rupee (e₹) — India Context
- Applications in Banking & Finance
- Indian Government Initiatives & Regulations
- Blockchain vs Traditional Database
- Advantages, Disadvantages & Challenges
- Quick Revision Sheet
- Interactive MCQ Practice Bank (65+ Questions)
Section 01
01What is Blockchain?
Core Definition
Blockchain is a distributed digital ledger (record book) that stores data in blocks which are linked together in a chain. Each block is secured using cryptography. The ledger is maintained across many computers simultaneously — so no single person or organisation controls it, and data recorded cannot be easily altered.
Simple Formula to Remember
Blockchain = Distributed Ledger + Linked Blocks + Cryptography + Immutability + No Central Authority
📖
Digital Ledger
Like an accounting book — but digital. Records every transaction or event in a permanent, verifiable way.
🌐
Distributed
The same ledger is stored on thousands of computers (nodes) worldwide — no single point of failure.
🔒
Tamper-Proof
Once data is added to a block and confirmed, altering it breaks the cryptographic link — making tampering instantly detectable.
👥
Decentralized
No bank, government, or single company controls blockchain. All participants jointly maintain the record.
🔍
Transparent
In public blockchains, any participant can verify any transaction — creating an open audit trail.
🤝
Trustless
Parties can transact without needing to trust each other — the protocol and math ensure trust automatically.
⚠️ Exam Alert — Most Frequently Tested
Blockchain was invented by Satoshi Nakamoto (pseudonym) in 2008 as the technology behind Bitcoin. Bitcoin’s blockchain is the world’s first and largest public blockchain. Blockchain ≠ Bitcoin — blockchain is the underlying technology.
Section 02
02Key Features of Blockchain
| Feature | Simple Meaning | Exam Relevance |
|---|---|---|
| Decentralized | No single central authority — all nodes jointly control the ledger | High |
| Distributed Ledger | Identical copy of the ledger stored across many computers/nodes simultaneously | High |
| Immutability | Data once written and confirmed cannot be changed or deleted without detection | High |
| Transparency | All participants can verify transactions (especially in public blockchains) | Medium |
| Cryptographic Security | Uses SHA-256 hashing and public-private key cryptography to secure data | High |
| Consensus Mechanism | All (or majority of) participants must agree before a block is added | High |
| Peer-to-Peer (P2P) | Transactions happen directly between parties — no intermediary needed | Medium |
| Smart Contracts | Self-executing code with predefined conditions — automates agreements | High |
| Pseudonymity | Participants use wallet addresses, not real names — partial privacy | Low–Med |
| Permissioned / Permissionless | Public blockchains = permissionless (anyone joins); Private = permissioned (approved only) | Medium |
Memory Trick — DDTIS-C
Decentralized · Distributed · Transparent · Immutable · Secure (cryptography) · Consensus-based
Section 03
03How a Blockchain Works — Structure of Blocks
What Each Block Contains:
| Component | What It Is | Why Important |
|---|---|---|
| Block Number / Index | Sequential number identifying the block’s position in the chain | Identifies block order |
| Transaction Data | The actual records stored — e.g., payment details, contract terms | Core content of the block |
| Timestamp | Date and time when the block was created | Proves when data was recorded |
| Hash (Current Block) | Unique digital fingerprint of this block’s contents — generated by SHA-256 | Ensures data integrity |
| Previous Block Hash | Hash of the block immediately before — creates the chain link | Makes tampering detectable |
| Nonce | A random number miners adjust to find a valid hash (used in Proof of Work) | Proof of computation in PoW mining |
| Merkle Root | A single hash summarising all transactions in the block using a Merkle Tree | Efficient verification of all transactions |
How Blocks Link Together:
Genesis Block
Block #0
Prev Hash0000…000
Hasha1b2c3…
DataFirst block
→
Block #1
Prev Hasha1b2c3…
Hashd4e5f6…
DataTx: A→B ₹500
→
Block #2
Prev Hashd4e5f6…
Hashg7h8i9…
DataTx: C→D ₹200
→
Block #3
Prev Hashg7h8i9…
Hashj0k1l2…
DataTx: E→F ₹800
Why Tampering is Impossible
If someone tries to alter Block #1, its hash changes → Block #2’s “Previous Hash” becomes invalid → every block after breaks → all nodes on the network reject it. Changing even one block would require re-computing every subsequent block AND outpacing the entire network — computationally impossible.
⚠️ Exam Alert — Key Terms
Genesis Block = First block in any blockchain (no previous hash — set to all zeros)Hash = Unique digital fingerprint of data (Bitcoin uses SHA-256)
Nonce = Number used Once — miners adjust this to find a valid hash
Merkle Tree / Merkle Root = Tree structure that summarises all transactions in a block for fast verification
Section 04
04Types of Blockchain Most Asked
Public Blockchain
Access: Anyone can join, read & write
Control: Fully decentralized — no owner
Consensus: PoW or PoS
Transparency: Fully public
Speed: Slower (many validators)
Examples: Bitcoin, Ethereum
Best for: Cryptocurrencies, DeFi
Private Blockchain
Access: Only invited/approved participants
Control: Single organization controls it
Consensus: PoA or custom
Transparency: Only for members
Speed: Faster (fewer validators)
Examples: Hyperledger Fabric, Corda
Best for: Enterprise, internal banking
Consortium Blockchain
Access: Group of pre-selected organizations
Control: Multiple organizations together
Consensus: PoA / BFT variants
Transparency: Semi-transparent
Speed: Fast
Examples: R3 Corda, Quorum
Best for: Inter-bank settlements, trade finance
| Type | Permission | Who Controls | Key Feature | Example Use in India |
|---|---|---|---|---|
| Public | Permissionless | No one / Everyone | Max decentralization & transparency | Cryptocurrency trading on exchanges |
| Private | Permissioned | Single organization | Fast, controlled, private | Internal bank ledger, corporate records |
| Consortium | Permissioned | Group of organizations | Shared control among trusted parties | Banking consortium for KYC / trade finance |
| Hybrid | Mixed | Organization + public rules | Choose what’s public vs private | Govt supply chain + private participant data |
Memory Trick — PPCH
Public · Private · Consortium · Hybrid — the four types of blockchain. Banks typically use Private or Consortium blockchains for enterprise applications.
Section 05
05Consensus Mechanisms Hot MCQ
What is a Consensus Mechanism?
A set of rules by which all (or a majority of) nodes in a blockchain network agree on the valid state of the ledger before adding a new block. Without consensus, there would be conflicting versions of the chain.
| Mechanism | Full Name | How It Works | Used By | Key Drawback |
|---|---|---|---|---|
| PoW Hot | Proof of Work | Miners compete to solve complex mathematical puzzles. First to solve adds the block and gets reward. | Bitcoin, Litecoin | Very high energy consumption (mining) |
| PoS Hot | Proof of Stake | Validators are chosen based on how many coins they “stake” (lock up as collateral). No mining required. | Ethereum 2.0, Cardano, Solana | Can favour wealthy validators (“rich get richer”) |
| DPoS | Delegated Proof of Stake | Token holders vote for a small group of delegates who validate blocks on their behalf. | EOS, TRON | Slightly more centralized |
| PoA | Proof of Authority | Only pre-approved, trusted validators (identified individuals/organizations) can validate blocks. | Private/enterprise blockchains, Hyperledger | Centralized — validators must be trusted |
| PBFT | Practical Byzantine Fault Tolerance | Works even when some nodes send incorrect/malicious data. Used in permissioned networks. | Hyperledger Fabric, Ripple | Doesn’t scale well with many nodes |
| PoET | Proof of Elapsed Time | Random wait timer given to each validator; the one whose timer expires first gets to add the block. | Hyperledger Sawtooth | Requires trusted hardware |
⛏️
Proof of Work (PoW)
Miners compete using computing power to solve a puzzle. Winner adds the block & gets Bitcoin reward. Secure but wastes energy. Bitcoin uses SHA-256 hashing.
🏦
Proof of Stake (PoS)
No mining — validators lock coins as stake. Chosen randomly (weighted by stake). 99% less energy than PoW. Ethereum switched to PoS in Sept 2022 (“The Merge”).
🏛️
Proof of Authority (PoA)
Only pre-vetted, known validators. Fast & efficient — ideal for banking & enterprise. Less decentralized but more suitable for regulated industries.
⚠️ Exam Traps — Know These Distinctions
PoW = Bitcoin · PoS = Ethereum 2.0 (after “The Merge” September 2022) · PoA = Private/Enterprise blockchains (banks)PoW consumes high energy (major criticism) · PoS uses ~99% less energy than PoW · 51% attack is a threat in PoW networks where one entity gains >50% mining power
Section 06
06Smart Contracts Exam Favourite
Definition
A Smart Contract is a self-executing program stored on a blockchain that automatically carries out predefined actions when specific conditions are met — with no human intervention or intermediary needed.
Simple Analogy
Smart Contract = Vending Machine. You put in money + select item → machine automatically gives you the item. Similarly, smart contracts automatically execute when conditions (like payment confirmation) are met.
| Feature | Detail |
|---|---|
| Invented by | Nick Szabo (concept, 1994) — widely deployed on Ethereum blockchain |
| Language | Written in Solidity (for Ethereum), Chaincode (for Hyperledger) |
| Execution | Runs automatically when coded conditions (If-Then-Else logic) are met |
| Immutable | Once deployed on blockchain, the code cannot be changed |
| Transparent | All parties can see the contract terms — no hidden clauses |
| No Middleman | No lawyer, bank officer, or notary required for execution |
Smart Contract Use Cases in Banking & Finance:
| Area | How Smart Contract Helps |
|---|---|
| Trade Finance (Letter of Credit) | Auto-releases payment when shipping documents are verified on-chain — removes manual processing |
| Loan Processing | Auto-disburses loan funds when KYC, credit score, and collateral conditions are met |
| Insurance Claims | Auto-pays claims when verified event (e.g., flight delay > 3 hours from airline data) is confirmed |
| Bond Coupon Payments | Automatically releases interest payments to bondholders on due dates |
| Real Estate | Transfers property ownership token when buyer’s payment is confirmed on-chain |
| DeFi (Decentralized Finance) | Enables lending, borrowing, and trading without banks — entirely run by smart contracts |
Section 07
07Cryptocurrency — Key Facts for Exams
Critical Distinction — Exam Trap
Blockchain ≠ Cryptocurrency. Blockchain is the underlying technology. Cryptocurrency is one application of blockchain. You can have blockchain without cryptocurrency (e.g., Hyperledger for supply chain). But you cannot have cryptocurrency without blockchain.
| Cryptocurrency | Founded | Key Feature | Consensus | Exam Point |
|---|---|---|---|---|
| Bitcoin (BTC) | 2009 by Satoshi Nakamoto | First cryptocurrency; store of value; limited supply of 21 million coins | Proof of Work (SHA-256) | World’s first & most popular crypto |
| Ethereum (ETH) | 2015 by Vitalik Buterin | Smart contracts platform; “programmable blockchain” | Proof of Stake (since Sept 2022) | Largest smart contract platform |
| Ripple (XRP) | 2012 by Ripple Labs | Cross-border payments for banks; very fast settlement (3–5 seconds) | RPCA (consensus protocol) | Widely used by banks for remittance |
| Litecoin (LTC) | 2011 by Charlie Lee | Faster than Bitcoin; lighter version | Proof of Work (Scrypt) | “Silver to Bitcoin’s Gold” |
| Stablecoins (USDT, USDC) | — | Pegged to stable asset (USD) — no price volatility | Various | Bridge between crypto and traditional finance |
India’s Crypto Tax Policy (Exam Relevant)
As per Union Budget 2022–23: Gains from Virtual Digital Assets (VDA = cryptocurrencies, NFTs) are taxed at flat 30%. TDS of 1% on transactions above ₹10,000. Losses from one VDA cannot be set off against gains from another. No deduction allowed except cost of acquisition.
Section 08
08CBDC & Digital Rupee (e₹) Hot MCQ
Definition — CBDC
CBDC (Central Bank Digital Currency) is a digital form of a country’s sovereign currency issued and regulated by the central bank. It is legal tender — same value as physical cash — but exists only in digital form. Unlike private cryptocurrency, CBDC is government-backed and centrally controlled.
🇮🇳 India’s Digital Rupee (e₹) — RBI CBDC
| Detail | Information |
|---|---|
| Full Name | Digital Rupee (e₹ / eINR) |
| Issued by | Reserve Bank of India (RBI) |
| Legal Tender Status | Yes — same as physical ₹ currency |
| Technology | Permissioned (private/consortium) blockchain — controlled by RBI |
| Pilot Launch (Wholesale) | November 2022 — e₹-W pilot for inter-bank government securities settlement |
| Pilot Launch (Retail) | December 2022 — e₹-R pilot for retail payments (launched in 4 cities initially) |
| Interest Bearing | No — e₹ does not earn interest (unlike bank deposits) |
| Anonymity | Partial — small transactions may be anonymous; large ones are traceable |
| Regulation | RBI Concept Note on CBDC (Oct 2022) provides the framework |
| Type | Full Form | Target Users | Purpose |
|---|---|---|---|
| e₹-W | CBDC-Wholesale | Banks and financial institutions | Large-value inter-bank settlements, government securities transactions |
| e₹-R | CBDC-Retail | General public, merchants | Day-to-day retail payments — P2P (person-to-person) and P2M (person-to-merchant) |
| Feature | Physical Cash (₹) | Digital Rupee (e₹) | Private Cryptocurrency |
|---|---|---|---|
| Issued by | RBI | RBI | No central issuer |
| Legal Tender | Yes | Yes | No (in India) |
| Physical form | Yes | No (digital only) | No |
| Volatility | Stable | Stable | Highly volatile |
| Regulated by RBI | Yes | Yes | No (in India) |
| Traceability | Limited | Partial to full | Pseudonymous |
| Earns Interest | No | No | Some (staking) |
⚠️ Exam Alert — CBDC Global Context
Countries with launched CBDC: Bahamas (Sand Dollar) — world’s first (2020); Nigeria (eNaira); Jamaica (JAM-DEX); China (Digital Yuan / e-CNY) — largest CBDC pilot globally. India (e₹) — pilot since 2022. US Federal Reserve is still researching a digital dollar.
Section 09
09Applications of Blockchain in Banking & Finance
| Application Area | How Blockchain Helps | Exam Relevance |
|---|---|---|
| Cross-border Payments / Remittance | Direct P2P transfer — no correspondent banks; faster (seconds vs days); lower fees; 24×7 availability | High |
| KYC (Know Your Customer) | Customer verifies once → KYC data stored on blockchain → shared across banks (with consent) → no repeated KYC | High |
| AML (Anti-Money Laundering) | Immutable transaction trail makes it easier to detect suspicious patterns; shared ledger enables cross-bank monitoring | Medium |
| Trade Finance | Smart contracts automate Letter of Credit (LC) workflow; reduces paperwork, forgery risk, and processing time from days to hours | High |
| Securities Settlement | T+0 or near-instant settlement vs traditional T+2 (two-day settlement); reduces counterparty risk | Medium |
| Fraud Detection | Immutable records make retroactive fraud harder; shared ledger detects duplicate transactions across institutions | High |
| Tokenization of Assets | Real estate, bonds, gold represented as digital tokens → easier fractional ownership and trading | Medium |
| CBDC / Digital Currency | Central bank-issued digital money on permissioned blockchain — Digital Rupee (e₹) in India | High |
| Supply Chain Finance | All parties see same trusted record of goods movement → auto-financing against verified invoices | Low–Med |
| Digital Bonds / Green Bonds | Bond issuance, tracking, and coupon payment automated via smart contracts; World Bank, SEBI exploring | Low–Med |
| Insurance | Parametric insurance — smart contracts auto-pay claims based on verified real-world data (e.g., rainfall sensors for crop insurance) | Medium |
India-Specific Blockchain in Finance
IDRBT (Institute for Development & Research in Banking Technology) has been piloting blockchain for trade finance and KYC in India. State Bank of India uses blockchain for Smart Contracts in trade finance. SEBI has been exploring blockchain for securities settlement. NSDL is using blockchain for land records and commodity tracking.
Section 10
10Indian Govt Initiatives & Regulations
🇮🇳 India & Blockchain — Policy Landscape
| Initiative / Law | Details | Exam Relevance |
|---|---|---|
| Digital Rupee (e₹) | RBI launched CBDC pilots in Nov 2022 (wholesale) & Dec 2022 (retail). Legal framework under amended RBI Act. | Very High |
| RBI Concept Note on CBDC | Released October 2022 — outlines India’s approach to CBDC, design choices, risks, and benefits | High |
| Crypto Tax (Budget 2022-23) | 30% tax on VDA gains; 1% TDS; no loss set-off; defines Virtual Digital Assets legally for the first time | Very High |
| National Blockchain Strategy | MeitY released a draft framework for blockchain adoption in government services (land records, certificates, supply chain) | Medium |
| Blockchain in Land Records | Andhra Pradesh, Telangana, and Maharashtra piloting blockchain for land registration to reduce fraud | Medium |
| NIC Blockchain Platform | National Informatics Centre (NIC) developed a blockchain platform for e-governance — used for certificate verification | Medium |
| PMLA + FIU-IND | Crypto exchanges must register with FIU-IND (Financial Intelligence Unit – India) under PMLA; report suspicious crypto transactions | High |
| SEBI & Blockchain | SEBI exploring Distributed Ledger Technology (DLT) for mutual fund record-keeping and bond settlements | Medium |
| Cryptocurrency Regulation | India has NOT banned crypto — but has NOT given it legal tender status. It is treated as a speculative asset taxed as VDA. No comprehensive crypto law yet (as of 2025). | Very High |
| IDRBT Blockchain Labs | RBI’s research arm IDRBT actively researches blockchain for banking — published reports on DLT applications in Indian banking | Low–Med |
⚠️ Exam Alert — Crypto Status in India
India has NOT banned cryptocurrency. It is legal to hold/trade but is NOT legal tender. Gains taxed at 30% + 1% TDS. Crypto exchanges must register with FIU-IND under PMLA. The government has been considering a comprehensive crypto regulation bill but it has not been passed yet (as of 2025). The only government-issued digital currency is e₹ (Digital Rupee) by RBI.
Section 11
11Blockchain vs Traditional Database
| Parameter | Blockchain | Traditional Database (e.g., SQL) |
|---|---|---|
| Control | Decentralized — no single owner | Centralized — administrator controls |
| Data Modification | Immutable — cannot change confirmed data | CRUD (Create, Read, Update, Delete) freely |
| Transparency | All nodes see same data (in public blockchains) | Only authorized users see data |
| Trust | Trustless — math/cryptography ensures trust | Trust in the administrator/organization |
| Speed | Slower (consensus required for each block) | Faster (single admin, no consensus) |
| Cost | Higher (computing for consensus) | Lower for simple applications |
| Single Point of Failure | None — distributed across many nodes | Yes — if central server fails, all data at risk |
| Best for | Multi-party, no-trust scenarios needing immutable record | Single-organization, high-speed, mutable data |
Section 12
12Advantages, Disadvantages & Challenges
✅
Advantages
✓ Tamper-proof immutable records
✓ No single point of failure
✓ Reduces fraud & data manipulation
✓ Faster cross-border settlements
✓ Eliminates middlemen — lower costs
✓ Transparent audit trail
✓ Enables smart contracts & automation
✓ Strong cryptographic security
✓ No single point of failure
✓ Reduces fraud & data manipulation
✓ Faster cross-border settlements
✓ Eliminates middlemen — lower costs
✓ Transparent audit trail
✓ Enables smart contracts & automation
✓ Strong cryptographic security
❌
Disadvantages
✗ High energy use (especially PoW)
✗ Slower than traditional databases
✗ Scalability issues — limited TPS
✗ Complex technology — hard to implement
✗ Data once added cannot be deleted (GDPR conflict)
✗ 51% attack risk in public chains
✗ No regulatory certainty in many countries
✗ High initial implementation cost
✗ Slower than traditional databases
✗ Scalability issues — limited TPS
✗ Complex technology — hard to implement
✗ Data once added cannot be deleted (GDPR conflict)
✗ 51% attack risk in public chains
✗ No regulatory certainty in many countries
✗ High initial implementation cost
⚠️
Challenges in India
⚡ No comprehensive crypto law yet
⚡ Regulatory uncertainty for fintechs
⚡ Privacy vs transparency conflict (DPDP Act)
⚡ Integration with legacy banking systems
⚡ Lack of awareness & skilled workforce
⚡ Risk of misuse in illegal transactions
⚡ Interoperability between different blockchains
⚡ Regulatory uncertainty for fintechs
⚡ Privacy vs transparency conflict (DPDP Act)
⚡ Integration with legacy banking systems
⚡ Lack of awareness & skilled workforce
⚡ Risk of misuse in illegal transactions
⚡ Interoperability between different blockchains
⚡ Quick Revision Sheet — Read Before Your Exam
What is Blockchain?
Distributed digital ledger · Blocks linked by cryptographic hashes · Immutable · Decentralized · Consensus-basedInvented By / When
Satoshi Nakamoto (pseudonym) · 2008 paper · First implemented as Bitcoin (2009)Block Contains
Block number · Data · Timestamp · Current Hash · Previous Hash · Nonce · Merkle RootGenesis Block
First block in any blockchain · No previous hash · Starting point of chain4 Types
Public (Bitcoin, Ethereum) · Private (Hyperledger) · Consortium (R3, Quorum) · HybridConsensus
PoW = Bitcoin (energy-heavy) · PoS = Ethereum 2.0 (energy-efficient) · PoA = Banks/enterprise · PBFT = Hyperledger51% Attack
Single entity controls >50% mining power → can double-spend or censor transactions. Major PoW risk.Smart Contract
Self-executing code · No middleman · Invented by Nick Szabo · Popularised by Ethereum · Written in SolidityBlockchain ≠ Crypto
Blockchain = technology platform · Cryptocurrency = ONE application of blockchainCBDC — e₹
RBI’s Digital Rupee · Legal tender · Permissioned blockchain · e₹-W (banks) + e₹-R (retail) · Pilot 2022India Crypto Tax
30% tax on VDA gains · 1% TDS above ₹10K · No loss set-off · Budget 2022–23Banking Uses
Cross-border payments · KYC sharing · Trade finance · Fraud detection · Securities settlement · CBDCFirst World CBDC
Bahamas — Sand Dollar (2020). China’s e-CNY = largest pilot. India’s e₹ pilot = 2022.Crypto + PMLA India
Crypto exchanges must register with FIU-IND · Report suspicious transactions under PMLA (since 2023)Ethereum “The Merge”
Sept 2022 — Ethereum switched from PoW to PoS · 99% less energy · Major blockchain milestoneKey Hashing Algorithm
Bitcoin uses SHA-256 · Produces 256-bit unique hash · One-way function · Collision resistant🧠
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📘 Chapter 1 — Basics & Core Concepts (Q1–Q15)
★ HOT
Q1. Blockchain is best described as a:
Answer: B — Distributed, shared, and immutable digital ledger secured by cryptography.
Blockchain stores identical copies of records at many nodes (computers), forming a shared ledger. Data once recorded cannot be easily changed.
Blockchain stores identical copies of records at many nodes (computers), forming a shared ledger. Data once recorded cannot be easily changed.
★ HOT
Q2. Who invented Bitcoin and the concept of blockchain?
Answer: C — Satoshi Nakamoto.
Satoshi Nakamoto is a pseudonym (real identity unknown) who published the Bitcoin whitepaper in 2008 and launched the Bitcoin network in January 2009.
Satoshi Nakamoto is a pseudonym (real identity unknown) who published the Bitcoin whitepaper in 2008 and launched the Bitcoin network in January 2009.
★ HOT
Q3. In blockchain, data is stored in units called:
Answer: C — Blocks.
Each block contains transaction data, a timestamp, the hash of the current block, and the hash of the previous block — creating the “chain” in blockchain.
Each block contains transaction data, a timestamp, the hash of the current block, and the hash of the previous block — creating the “chain” in blockchain.
★ HOT
Q4. The FIRST block in any blockchain is called:
Answer: B — Genesis Block.
The Genesis Block is Block #0 — the starting point of any blockchain. It has no “previous hash” (set to all zeros) since there is no block before it.
The Genesis Block is Block #0 — the starting point of any blockchain. It has no “previous hash” (set to all zeros) since there is no block before it.
★ HOT
Q5. What makes blockchain data tamper-proof?
Answer: B — Hash chain linking.
Each block contains the hash of the previous block. Changing Block #2’s data changes its hash → Block #3’s “Previous Hash” becomes invalid → every block after is broken → all nodes reject it.
Each block contains the hash of the previous block. Changing Block #2’s data changes its hash → Block #3’s “Previous Hash” becomes invalid → every block after is broken → all nodes reject it.
Q6
Q6. “Decentralization” in blockchain means:
Answer: B — No single central authority.
Thousands of computers (nodes) worldwide maintain identical copies of the blockchain. No single node has complete control — this eliminates single points of failure or control.
Thousands of computers (nodes) worldwide maintain identical copies of the blockchain. No single node has complete control — this eliminates single points of failure or control.
Q7
Q7. Which technology is fundamental to securing blockchain data?
Answer: B — Cryptography.
Blockchain uses cryptographic hash functions (SHA-256 for Bitcoin) and public-private key pairs to secure data, link blocks, and authenticate transactions without a central authority.
Blockchain uses cryptographic hash functions (SHA-256 for Bitcoin) and public-private key pairs to secure data, link blocks, and authenticate transactions without a central authority.
★ HOT
Q8. The “double-spending problem” in digital money refers to:
Answer: B — Double-spending of digital currency.
Unlike physical cash, digital files can be copied. Without blockchain, a digital coin could be spent twice. Blockchain’s consensus mechanism ensures each coin can only be spent once, globally.
Unlike physical cash, digital files can be copied. Without blockchain, a digital coin could be spent twice. Blockchain’s consensus mechanism ensures each coin can only be spent once, globally.
Q9
Q9. “Immutability” in blockchain means:
Answer: C — Cannot be altered or deleted.
Immutability is one of blockchain’s defining features. This property makes it ideal for financial records, audit trails, and any application where permanent, tamper-proof records are required.
Immutability is one of blockchain’s defining features. This property makes it ideal for financial records, audit trails, and any application where permanent, tamper-proof records are required.
Q10
Q10. Which of these is NOT a core feature of blockchain?
Answer: B — Single centralized control.
The defining feature of blockchain is decentralization — no single entity controls it. Central control is exactly what blockchain eliminates.
The defining feature of blockchain is decentralization — no single entity controls it. Central control is exactly what blockchain eliminates.
Q11
Q11. Hashing algorithm used by Bitcoin blockchain is:
Answer: B — SHA-256.
Bitcoin uses SHA-256 (Secure Hash Algorithm 256-bit) to generate hashes for blocks. It produces a unique 256-bit (64 hexadecimal character) fingerprint for any input data.
Bitcoin uses SHA-256 (Secure Hash Algorithm 256-bit) to generate hashes for blocks. It produces a unique 256-bit (64 hexadecimal character) fingerprint for any input data.
Q12
Q12. A “Merkle Root” in a blockchain block is:
Answer: B — A single hash summarizing all transactions.
Merkle Tree is a binary hash tree where each transaction is hashed, hashes are paired and re-hashed up to the root. The Merkle Root allows efficient verification that a specific transaction is in the block.
Merkle Tree is a binary hash tree where each transaction is hashed, hashes are paired and re-hashed up to the root. The Merkle Root allows efficient verification that a specific transaction is in the block.
Q13
Q13. “Nonce” in blockchain (Proof of Work) refers to:
Answer: B — A number miners adjust to solve the PoW puzzle.
Nonce = Number Used Once. Miners try billions of nonce values until the block’s hash starts with enough zeros (difficulty target) — proving computational work was done.
Nonce = Number Used Once. Miners try billions of nonce values until the block’s hash starts with enough zeros (difficulty target) — proving computational work was done.
Q14
Q14. A “node” in a blockchain network is:
Answer: B — Any participating computer maintaining the ledger.
Nodes are participants in the blockchain network. Full nodes store the entire blockchain, validate transactions, and help maintain decentralization. Anyone can run a node on public blockchains like Bitcoin.
Nodes are participants in the blockchain network. Full nodes store the entire blockchain, validate transactions, and help maintain decentralization. Anyone can run a node on public blockchains like Bitcoin.
Q15
Q15. A “51% attack” on a public blockchain occurs when:
Answer: B — Majority mining power control enabling double-spending.
In PoW blockchains, whoever controls >50% computing power can rewrite transaction history, reverse transactions, and double-spend coins. This is a theoretical threat that makes large blockchains like Bitcoin very secure (too costly to attack).
In PoW blockchains, whoever controls >50% computing power can rewrite transaction history, reverse transactions, and double-spend coins. This is a theoretical threat that makes large blockchains like Bitcoin very secure (too costly to attack).
📗 Chapter 2 — Types of Blockchain & Consensus (Q16–Q30)
★ HOT
Q16. A public blockchain is best defined as:
Answer: B — Open, permissionless network.
Public blockchains like Bitcoin and Ethereum allow anyone to join, validate transactions, and view the ledger without permission. They offer maximum decentralization and transparency.
Public blockchains like Bitcoin and Ethereum allow anyone to join, validate transactions, and view the ledger without permission. They offer maximum decentralization and transparency.
★ HOT
Q17. A consortium blockchain is managed by:
Answer: B — A group of pre-selected organizations.
Consortium (federated) blockchains are controlled by multiple organizations together — e.g., multiple banks forming a blockchain for inter-bank KYC or trade finance. Examples: R3 Corda, Quorum.
Consortium (federated) blockchains are controlled by multiple organizations together — e.g., multiple banks forming a blockchain for inter-bank KYC or trade finance. Examples: R3 Corda, Quorum.
Q18
Q18. Which blockchain type is MOST suitable for banking KYC sharing between multiple banks?
Answer: B — Consortium blockchain.
Banks need to share KYC data with each other but NOT with the general public. A consortium blockchain (permissioned, shared among trusted institutions) balances transparency among members with privacy from outsiders.
Banks need to share KYC data with each other but NOT with the general public. A consortium blockchain (permissioned, shared among trusted institutions) balances transparency among members with privacy from outsiders.
★ HOT
Q19. Proof of Work (PoW) consensus requires miners to:
Answer: B — Solve computational puzzles.
In PoW, miners compete to find a nonce that makes the block’s hash meet the difficulty target (e.g., starting with many zeros). The winner adds the block and receives a block reward. Used by Bitcoin.
In PoW, miners compete to find a nonce that makes the block’s hash meet the difficulty target (e.g., starting with many zeros). The winner adds the block and receives a block reward. Used by Bitcoin.
★ HOT
Q20. The MAIN disadvantage of Proof of Work (PoW) is:
Answer: B — Extremely high energy consumption.
PoW’s competitive mining process requires massive computing power running continuously, consuming huge amounts of electricity. This is the primary environmental criticism of Bitcoin and a major reason Ethereum switched to PoS.
PoW’s competitive mining process requires massive computing power running continuously, consuming huge amounts of electricity. This is the primary environmental criticism of Bitcoin and a major reason Ethereum switched to PoS.
★ HOT
Q21. Ethereum switched from Proof of Work to Proof of Stake in:
Answer: B — September 2022 (“The Merge”).
“The Merge” in September 2022 was Ethereum’s transition from energy-intensive PoW to eco-friendly PoS. This reduced Ethereum’s energy consumption by approximately 99.95%.
“The Merge” in September 2022 was Ethereum’s transition from energy-intensive PoW to eco-friendly PoS. This reduced Ethereum’s energy consumption by approximately 99.95%.
Q22
Q22. In Proof of Stake (PoS), validators are chosen based on:
Answer: B — Amount of cryptocurrency staked.
In PoS, validators lock up coins as collateral. They are selected (often randomly but weighted by stake size) to propose and validate blocks. Misbehavior results in losing staked funds (“slashing”).
In PoS, validators lock up coins as collateral. They are selected (often randomly but weighted by stake size) to propose and validate blocks. Misbehavior results in losing staked funds (“slashing”).
Q23
Q23. Proof of Authority (PoA) is most suitable for:
Answer: B — Private and enterprise blockchains.
PoA delegates validation authority to pre-approved, identity-verified validators. It’s fast, energy-efficient, and suitable for banking consortiums and enterprise applications where participants are known.
PoA delegates validation authority to pre-approved, identity-verified validators. It’s fast, energy-efficient, and suitable for banking consortiums and enterprise applications where participants are known.
Q24
Q24. Hyperledger Fabric is an example of which type of blockchain?
Answer: B — Private/permissioned enterprise blockchain.
Hyperledger Fabric (by Linux Foundation, backed by IBM) is a permissioned blockchain framework designed for enterprise use — banks, supply chains, healthcare. It has no native cryptocurrency.
Hyperledger Fabric (by Linux Foundation, backed by IBM) is a permissioned blockchain framework designed for enterprise use — banks, supply chains, healthcare. It has no native cryptocurrency.
★ EXPECTED
Q25. PBFT (Practical Byzantine Fault Tolerance) in blockchain means the network can still function correctly even when:
Answer: B — Tolerates faulty/malicious nodes (up to 1/3).
PBFT allows the network to reach consensus even if some nodes are faulty or malicious — as long as less than 1/3 of nodes behave badly. Used in Hyperledger Fabric and Ripple for fast, finality-guaranteed consensus in permissioned networks.
PBFT allows the network to reach consensus even if some nodes are faulty or malicious — as long as less than 1/3 of nodes behave badly. Used in Hyperledger Fabric and Ripple for fast, finality-guaranteed consensus in permissioned networks.
📙 Chapter 3 — Smart Contracts & Cryptocurrency (Q26–Q40)
★ HOT
Q26. A Smart Contract is BEST defined as:
Answer: B — Self-executing blockchain program.
Smart contracts execute automatically when conditions are met — like a vending machine. No human intermediary (lawyer, bank officer) is needed. First deployed widely on Ethereum. Written in Solidity language.
Smart contracts execute automatically when conditions are met — like a vending machine. No human intermediary (lawyer, bank officer) is needed. First deployed widely on Ethereum. Written in Solidity language.
Q27
Q27. Smart Contracts were conceptually invented by:
Answer: B — Nick Szabo (concept) / Vitalik Buterin (implementation).
Nick Szabo coined the term “Smart Contract” in 1994. Vitalik Buterin created Ethereum (2015) — the first blockchain to widely implement smart contracts using the Solidity programming language.
Nick Szabo coined the term “Smart Contract” in 1994. Vitalik Buterin created Ethereum (2015) — the first blockchain to widely implement smart contracts using the Solidity programming language.
Q28
Q28. In trade finance, smart contracts can automate which process?
Answer: B — Letter of Credit automation.
Traditional LC process takes 5–10 days with physical documents. Smart contracts can verify shipping milestones on-chain and automatically release payment — reducing LC settlement to hours.
Traditional LC process takes 5–10 days with physical documents. Smart contracts can verify shipping milestones on-chain and automatically release payment — reducing LC settlement to hours.
★ HOT
Q29. Which statement is CORRECT about blockchain and cryptocurrency?
Answer: C — Blockchain is the tech; crypto is one use.
Blockchain has countless uses beyond cryptocurrency: KYC, trade finance, supply chain, land records, healthcare, etc. Private/consortium blockchains used by banks don’t even have a cryptocurrency component.
Blockchain has countless uses beyond cryptocurrency: KYC, trade finance, supply chain, land records, healthcare, etc. Private/consortium blockchains used by banks don’t even have a cryptocurrency component.
Q30
Q30. Ethereum was founded by:
Answer: B — Vitalik Buterin, 2015.
Vitalik Buterin, a Canadian-Russian programmer, conceptualized Ethereum in 2013 and launched it in 2015. Ethereum introduced programmable smart contracts to the blockchain world and is now the second-largest cryptocurrency by market cap.
Vitalik Buterin, a Canadian-Russian programmer, conceptualized Ethereum in 2013 and launched it in 2015. Ethereum introduced programmable smart contracts to the blockchain world and is now the second-largest cryptocurrency by market cap.
Q31
Q31. Ripple (XRP) is primarily used for:
Answer: B — Cross-border payments for financial institutions.
Ripple (XRP Ledger) focuses on fast, low-cost international money transfer for banks. Many banks use RippleNet to settle cross-border transactions in seconds vs days for traditional SWIFT transfers.
Ripple (XRP Ledger) focuses on fast, low-cost international money transfer for banks. Many banks use RippleNet to settle cross-border transactions in seconds vs days for traditional SWIFT transfers.
Q32
Q32. Bitcoin has a maximum supply limit of:
Answer: B — 21 million Bitcoin.
Bitcoin’s maximum supply is hardcoded at 21 million coins — making it a deflationary asset (unlike fiat currencies which can be printed infinitely). This scarcity is one reason why Bitcoin is called “digital gold.”
Bitcoin’s maximum supply is hardcoded at 21 million coins — making it a deflationary asset (unlike fiat currencies which can be printed infinitely). This scarcity is one reason why Bitcoin is called “digital gold.”
★ EXPECTED
Q33. A “stablecoin” in cryptocurrency is:
Answer: B — Crypto pegged to a stable asset.
Stablecoins (USDT, USDC) maintain a 1:1 peg to a stable currency like USD, reducing the wild price swings of Bitcoin/Ethereum. They bridge traditional finance and DeFi, widely used in crypto trading and remittances.
Stablecoins (USDT, USDC) maintain a 1:1 peg to a stable currency like USD, reducing the wild price swings of Bitcoin/Ethereum. They bridge traditional finance and DeFi, widely used in crypto trading and remittances.
Q34
Q34. NFT (Non-Fungible Token) refers to:
Answer: B — Unique digital asset proving digital ownership.
Unlike fungible tokens (1 Bitcoin = 1 Bitcoin), each NFT is unique and non-interchangeable. NFTs prove digital ownership of art, music, game items, domain names, etc. on the blockchain — primarily on Ethereum.
Unlike fungible tokens (1 Bitcoin = 1 Bitcoin), each NFT is unique and non-interchangeable. NFTs prove digital ownership of art, music, game items, domain names, etc. on the blockchain — primarily on Ethereum.
★ EXPECTED
Q35. DeFi (Decentralized Finance) refers to:
Answer: B — Financial services via smart contracts, no banks.
DeFi protocols (Uniswap, Aave, Compound) run entirely on smart contracts. Users can lend, borrow, earn interest, and trade crypto assets without any bank or financial intermediary — 24/7, globally accessible.
DeFi protocols (Uniswap, Aave, Compound) run entirely on smart contracts. Users can lend, borrow, earn interest, and trade crypto assets without any bank or financial intermediary — 24/7, globally accessible.
📕 Chapter 4 — CBDC, Digital Rupee & India Context (Q36–Q50)
★ HOT
Q36. CBDC stands for:
Answer: B — Central Bank Digital Currency.
CBDC is a digital form of a country’s sovereign currency issued and guaranteed by the central bank. Unlike private cryptocurrency, it has legal tender status and is fully regulated.
CBDC is a digital form of a country’s sovereign currency issued and guaranteed by the central bank. Unlike private cryptocurrency, it has legal tender status and is fully regulated.
★ HOT
Q37. India’s Digital Rupee (e₹) is issued by:
Answer: B — Reserve Bank of India (RBI).
The Digital Rupee (e₹) is India’s CBDC issued by RBI. It is legal tender — same value as physical ₹ currency — but exists only in digital form on a permissioned blockchain controlled by RBI.
The Digital Rupee (e₹) is India’s CBDC issued by RBI. It is legal tender — same value as physical ₹ currency — but exists only in digital form on a permissioned blockchain controlled by RBI.
★ HOT
Q38. RBI launched the Digital Rupee Wholesale (e₹-W) pilot in:
Answer: B — November 2022.
RBI launched the e₹-W (Wholesale CBDC) pilot in November 2022 for government securities settlement. The e₹-R (Retail CBDC) pilot followed in December 2022, starting in 4 cities with select banks.
RBI launched the e₹-W (Wholesale CBDC) pilot in November 2022 for government securities settlement. The e₹-R (Retail CBDC) pilot followed in December 2022, starting in 4 cities with select banks.
★ HOT
Q39. e₹-W (Wholesale CBDC) is primarily meant for:
Answer: B — Inter-bank and large-value settlements.
e₹-W is designed for the wholesale segment — banks and financial institutions use it for inter-bank settlement of government securities. e₹-R (retail) is for everyday public use.
e₹-W is designed for the wholesale segment — banks and financial institutions use it for inter-bank settlement of government securities. e₹-R (retail) is for everyday public use.
★ HOT
Q40. How is the Digital Rupee (e₹) DIFFERENT from a private cryptocurrency like Bitcoin?
Answer: B — e₹ is government-backed legal tender; Bitcoin is not.
Key differences: e₹ is centralized (RBI controls), stable value (equals physical ₹), legal tender, regulated. Bitcoin is decentralized, volatile, no central issuer, NOT legal tender in India.
Key differences: e₹ is centralized (RBI controls), stable value (equals physical ₹), legal tender, regulated. Bitcoin is decentralized, volatile, no central issuer, NOT legal tender in India.
Q41
Q41. The world’s FIRST officially launched CBDC was:
Answer: B — Bahamas’ Sand Dollar (2020).
The Bahamas launched the Sand Dollar in October 2020 — making it the world’s first fully operational CBDC. China’s e-CNY is the largest CBDC pilot but was launched as a pilot. The US has not yet launched a digital dollar.
The Bahamas launched the Sand Dollar in October 2020 — making it the world’s first fully operational CBDC. China’s e-CNY is the largest CBDC pilot but was launched as a pilot. The US has not yet launched a digital dollar.
★ HOT
Q42. Under India’s Budget 2022-23, gains from Virtual Digital Assets (cryptocurrency, NFTs) are taxed at:
Answer: B — 30% flat tax.
Budget 2022-23 introduced 30% flat tax on VDA gains (cryptocurrency, NFTs) + 1% TDS on transactions above ₹10,000. Losses from one VDA cannot be set off against gains from another VDA. First time India legally defined Virtual Digital Assets.
Budget 2022-23 introduced 30% flat tax on VDA gains (cryptocurrency, NFTs) + 1% TDS on transactions above ₹10,000. Losses from one VDA cannot be set off against gains from another VDA. First time India legally defined Virtual Digital Assets.
★ HOT
Q43. Cryptocurrency exchanges in India are required to register with which body under PMLA?
Answer: B — FIU-IND under PMLA.
From March 2023, crypto exchanges operating in India must register with FIU-IND (Financial Intelligence Unit – India) as Reporting Entities under PMLA (Prevention of Money Laundering Act). They must report suspicious transactions.
From March 2023, crypto exchanges operating in India must register with FIU-IND (Financial Intelligence Unit – India) as Reporting Entities under PMLA (Prevention of Money Laundering Act). They must report suspicious transactions.
Q44
Q44. India’s legal status of cryptocurrency (as of 2025) is:
Answer: B — Legal but not legal tender; taxed as VDA.
India has NOT banned cryptocurrency. You can buy/sell/hold crypto legally. But it is NOT legal tender — you cannot use Bitcoin to buy groceries. Gains taxed at 30% as Virtual Digital Asset (VDA) under Income Tax Act.
India has NOT banned cryptocurrency. You can buy/sell/hold crypto legally. But it is NOT legal tender — you cannot use Bitcoin to buy groceries. Gains taxed at 30% as Virtual Digital Asset (VDA) under Income Tax Act.
Q45
Q45. Which Indian government body has drafted a National Blockchain Strategy for government services?
Answer: B — MeitY.
MeitY (Ministry of Electronics and IT) released a draft National Blockchain Strategy framework for adopting blockchain in government services including land records, certificates, identity verification, and supply chain.
MeitY (Ministry of Electronics and IT) released a draft National Blockchain Strategy framework for adopting blockchain in government services including land records, certificates, identity verification, and supply chain.
📒 Chapter 5 — Banking Applications & Advanced MCQs (Q46–Q65)
★ HOT
Q46. The main advantage of blockchain for cross-border payments is:
Answer: B — Direct P2P transfer, no intermediaries needed.
Traditional SWIFT cross-border payments involve multiple correspondent banks, take 3–5 business days, and charge high fees. Blockchain-based transfers can settle in minutes/seconds at a fraction of the cost.
Traditional SWIFT cross-border payments involve multiple correspondent banks, take 3–5 business days, and charge high fees. Blockchain-based transfers can settle in minutes/seconds at a fraction of the cost.
★ HOT
Q47. How does blockchain improve KYC (Know Your Customer) in banking?
Answer: B — Shared, verified KYC across institutions with consent.
Currently, banks repeat KYC for each new customer — wasting time and money. Blockchain KYC lets a customer verify once; verified data is stored on-chain and securely shared with other banks (only with customer consent), reducing onboarding time from days to minutes.
Currently, banks repeat KYC for each new customer — wasting time and money. Blockchain KYC lets a customer verify once; verified data is stored on-chain and securely shared with other banks (only with customer consent), reducing onboarding time from days to minutes.
Q48
Q48. “Tokenization of assets” in blockchain means:
Answer: B — Real-world assets as blockchain digital tokens.
Tokenization allows assets like real estate (normally indivisible) to be split into thousands of digital tokens — enabling fractional ownership, 24/7 trading, and instant settlement. E.g., owning ₹1000 worth of a ₹1 crore property.
Tokenization allows assets like real estate (normally indivisible) to be split into thousands of digital tokens — enabling fractional ownership, 24/7 trading, and instant settlement. E.g., owning ₹1000 worth of a ₹1 crore property.
Q49
Q49. In securities settlement, blockchain can reduce settlement time to:
Answer: B — T+0 or near-instant.
Current equity settlement is T+2 (trade + 2 business days) with multiple intermediaries. Blockchain enables near-instant (T+0) settlement, eliminating settlement risk and the capital tied up during the settlement window. SEBI is exploring this for Indian markets.
Current equity settlement is T+2 (trade + 2 business days) with multiple intermediaries. Blockchain enables near-instant (T+0) settlement, eliminating settlement risk and the capital tied up during the settlement window. SEBI is exploring this for Indian markets.
★ EXPECTED
Q50. Distributed Ledger Technology (DLT) is related to blockchain as:
Answer: B — Blockchain is a type of DLT.
DLT (Distributed Ledger Technology) is the umbrella term for any system that distributes records across multiple nodes. Blockchain (with its linked, hashed blocks) is the most famous DLT implementation. Other DLTs like Directed Acyclic Graph (DAG) used by IOTA also exist.
DLT (Distributed Ledger Technology) is the umbrella term for any system that distributes records across multiple nodes. Blockchain (with its linked, hashed blocks) is the most famous DLT implementation. Other DLTs like Directed Acyclic Graph (DAG) used by IOTA also exist.
Q51
Q51. Which Indian institution research blockchain applications for banking?
Answer: B — IDRBT.
IDRBT (Institute for Development and Research in Banking Technology), established by RBI, actively researches blockchain/DLT for banking applications including trade finance, KYC, and payment systems in the Indian context.
IDRBT (Institute for Development and Research in Banking Technology), established by RBI, actively researches blockchain/DLT for banking applications including trade finance, KYC, and payment systems in the Indian context.
Q52
Q52. Parametric crop insurance using blockchain in India can automatically pay farmers when:
Answer: B — Auto-payment via smart contract based on verified data.
Parametric insurance uses real-world data (rainfall sensors, satellite data) fed into smart contracts. If rainfall drops below a preset threshold, the smart contract automatically transfers the claim amount to the farmer’s account — no paperwork, no delays.
Parametric insurance uses real-world data (rainfall sensors, satellite data) fed into smart contracts. If rainfall drops below a preset threshold, the smart contract automatically transfers the claim amount to the farmer’s account — no paperwork, no delays.
Q53
Q53. A major conflict between blockchain’s immutability and data protection law is:
Answer: B — Right to Erasure vs. blockchain immutability conflict.
GDPR’s “Right to be Forgotten” and India’s DPDP Act’s right to erasure require personal data to be deletable. But blockchain data cannot be deleted once confirmed. Solutions include: storing only hashes on-chain (not personal data itself), or using private/permissioned blockchains with governance mechanisms.
GDPR’s “Right to be Forgotten” and India’s DPDP Act’s right to erasure require personal data to be deletable. But blockchain data cannot be deleted once confirmed. Solutions include: storing only hashes on-chain (not personal data itself), or using private/permissioned blockchains with governance mechanisms.
Q54
Q54. Which state in India has piloted blockchain for land record management?
Answer: B — Andhra Pradesh and Telangana.
Andhra Pradesh and Telangana have piloted blockchain for land registration records to reduce fraud, forgery, and disputes. Maharashtra has also worked on similar initiatives. Blockchain creates an immutable record of ownership transfers.
Andhra Pradesh and Telangana have piloted blockchain for land registration records to reduce fraud, forgery, and disputes. Maharashtra has also worked on similar initiatives. Blockchain creates an immutable record of ownership transfers.
★ EXPECTED
Q55. The main scalability challenge of blockchain is that:
Answer: B — Limited transactions per second (TPS).
Bitcoin processes ~7 TPS; Ethereum ~15–30 TPS; Visa processes ~24,000 TPS. This scalability gap is a major challenge for blockchain adoption in high-volume payment systems. Solutions: Layer 2 networks (Lightning Network for Bitcoin), sharding (Ethereum 2.0), Solana (~65,000 TPS).
Bitcoin processes ~7 TPS; Ethereum ~15–30 TPS; Visa processes ~24,000 TPS. This scalability gap is a major challenge for blockchain adoption in high-volume payment systems. Solutions: Layer 2 networks (Lightning Network for Bitcoin), sharding (Ethereum 2.0), Solana (~65,000 TPS).
Q56
Q56. “Mining” in Proof of Work blockchain refers to:
Answer: B — Using computing power to validate blocks and earn crypto rewards.
Miners run specialized hardware (ASICs for Bitcoin) solving SHA-256 puzzles. The winner adds the block and earns block reward (currently 3.125 BTC after April 2024 halving) + transaction fees. This secures the network through computational work.
Miners run specialized hardware (ASICs for Bitcoin) solving SHA-256 puzzles. The winner adds the block and earns block reward (currently 3.125 BTC after April 2024 halving) + transaction fees. This secures the network through computational work.
★ EXPECTED
Q57. “Bitcoin Halving” refers to:
Answer: B — Block reward cuts in half every ~4 years.
Bitcoin halvings occur every 210,000 blocks (~4 years). The most recent halving was April 2024 — reducing the block reward from 6.25 BTC to 3.125 BTC. This controls inflation and enforces Bitcoin’s scarcity (max 21 million BTC). Halvings are associated with price cycles.
Bitcoin halvings occur every 210,000 blocks (~4 years). The most recent halving was April 2024 — reducing the block reward from 6.25 BTC to 3.125 BTC. This controls inflation and enforces Bitcoin’s scarcity (max 21 million BTC). Halvings are associated with price cycles.
Q58
Q58. “Blockchain Interoperability” refers to:
Answer: B — Different blockchains communicating and sharing data.
Today Bitcoin, Ethereum, and Hyperledger are separate systems that can’t natively interact. Interoperability solutions (Polkadot, Cosmos, cross-chain bridges) allow assets and data to move between blockchains — critical for enterprise and banking adoption.
Today Bitcoin, Ethereum, and Hyperledger are separate systems that can’t natively interact. Interoperability solutions (Polkadot, Cosmos, cross-chain bridges) allow assets and data to move between blockchains — critical for enterprise and banking adoption.
Q59
Q59. “Web3” in the context of blockchain refers to:
Answer: B — Decentralized internet on blockchain.
Web1 = Read-only internet. Web2 = Read-write (social media, platforms own your data). Web3 = Read-write-own — users control their own data and digital assets through blockchain, smart contracts, and tokens.
Web1 = Read-only internet. Web2 = Read-write (social media, platforms own your data). Web3 = Read-write-own — users control their own data and digital assets through blockchain, smart contracts, and tokens.
★ HOT
Q60. Which of the following is correct about Ethereum compared to Bitcoin?
Answer: B — Ethereum supports smart contracts; Bitcoin primarily is digital money.
Bitcoin (2009) = Digital currency + store of value. Ethereum (2015) = Programmable blockchain platform supporting smart contracts, DApps, NFTs, DeFi, DAOs. Bitcoin uses PoW; Ethereum uses PoS (since Sept 2022).
Bitcoin (2009) = Digital currency + store of value. Ethereum (2015) = Programmable blockchain platform supporting smart contracts, DApps, NFTs, DeFi, DAOs. Bitcoin uses PoW; Ethereum uses PoS (since Sept 2022).
Q61
Q61. A “wallet” in cryptocurrency refers to:
Answer: B — Software/hardware storing private and public keys.
A crypto wallet doesn’t store cryptocurrency (which lives on the blockchain) — it stores the cryptographic keys that prove ownership and allow transactions. Hot wallets (online) are convenient; cold wallets (hardware, offline) are more secure.
A crypto wallet doesn’t store cryptocurrency (which lives on the blockchain) — it stores the cryptographic keys that prove ownership and allow transactions. Hot wallets (online) are convenient; cold wallets (hardware, offline) are more secure.
Q62
Q62. “Hard Fork” in blockchain means:
Answer: B — Backward-incompatible protocol change creating a chain split.
A Hard Fork results in two separate blockchains when the community disagrees on protocol changes. Famous examples: Bitcoin vs Bitcoin Cash (2017); Ethereum vs Ethereum Classic (2016 after the DAO hack).
A Hard Fork results in two separate blockchains when the community disagrees on protocol changes. Famous examples: Bitcoin vs Bitcoin Cash (2017); Ethereum vs Ethereum Classic (2016 after the DAO hack).
★ EXPECTED
Q63. “DAO” (Decentralized Autonomous Organization) in blockchain context is:
Answer: B — Organization governed by smart contracts and token holder votes.
A DAO has no CEO or traditional hierarchy. Governance decisions (how to spend funds, change rules) are made by token holders voting on-chain. Smart contracts automatically execute approved decisions. MakerDAO (issues DAI stablecoin) is a famous example.
A DAO has no CEO or traditional hierarchy. Governance decisions (how to spend funds, change rules) are made by token holders voting on-chain. Smart contracts automatically execute approved decisions. MakerDAO (issues DAI stablecoin) is a famous example.
Q64
Q64. Which of the following correctly differentiates blockchain from traditional databases for exam purposes?
Answer: B — Core architecture differences.
The key distinction: Blockchain = trustless, immutable, decentralized (ideal for multi-party, no-trust scenarios). Traditional DB = fast, flexible, efficient (ideal for single-organization, high-speed, mutable data needs).
The key distinction: Blockchain = trustless, immutable, decentralized (ideal for multi-party, no-trust scenarios). Traditional DB = fast, flexible, efficient (ideal for single-organization, high-speed, mutable data needs).
★ HOT
Q65. Which is the most comprehensive and accurate statement about blockchain’s role in Indian banking and finance?
Answer: B — Blockchain as a complementary technology with real use-cases and real challenges.
This is the balanced exam-ready answer. Blockchain is not a replacement but a complement to banking infrastructure — offering specific advantages (shared ledger, immutability, smart contracts) while facing genuine challenges (scalability, regulation, integration). India’s Digital Rupee is the most significant blockchain-related development in Indian banking.
This is the balanced exam-ready answer. Blockchain is not a replacement but a complement to banking infrastructure — offering specific advantages (shared ledger, immutability, smart contracts) while facing genuine challenges (scalability, regulation, integration). India’s Digital Rupee is the most significant blockchain-related development in Indian banking.
Master Reference
✓All Key Facts at a Glance
| Topic | Key Fact |
|---|---|
| Blockchain Invented | Satoshi Nakamoto, 2008 (Bitcoin whitepaper) |
| First Blockchain Use | Bitcoin launched January 3, 2009 |
| Genesis Block | First block in any blockchain — no previous hash (set to zeros) |
| Hash Algorithm (Bitcoin) | SHA-256 (256-bit hash) |
| Nonce | Number Used Once — adjusted by miners to find valid hash |
| 4 Types of Blockchain | Public · Private · Consortium (Federated) · Hybrid |
| PoW Used By | Bitcoin — high energy, mining-based consensus |
| PoS Used By | Ethereum 2.0 — since “The Merge” September 2022 |
| PoA Used By | Private/enterprise blockchains — banks, Hyperledger |
| 51% Attack | Single entity controls >50% hashing power → double-spending risk |
| Smart Contract | Nick Szabo (concept 1994) · Ethereum (deployed 2015) · Written in Solidity |
| Ethereum Founder | Vitalik Buterin — launched 2015 |
| Bitcoin Max Supply | 21 million coins — hardcoded limit |
| Bitcoin Halving | Every ~4 years (210,000 blocks) — latest April 2024 (reward: 3.125 BTC) |
| CBDC — India | Digital Rupee (e₹) by RBI · e₹-W pilot Nov 2022 · e₹-R pilot Dec 2022 |
| World’s First CBDC | Bahamas — Sand Dollar (2020) |
| Largest CBDC Pilot | China — Digital Yuan (e-CNY) |
| India Crypto Tax | 30% flat + 1% TDS (above ₹10K) · Budget 2022–23 |
| Crypto + PMLA India | Exchanges must register with FIU-IND (since March 2023) |
| Hyperledger Fabric | Private/permissioned enterprise blockchain · Linux Foundation · No native crypto |
| Ripple (XRP) | Cross-border bank payments · Settles in 3–5 seconds |
| NFT | Non-Fungible Token — unique digital asset proving ownership; primarily on Ethereum |
| DeFi | Decentralized Finance — financial services via smart contracts, no banks |
| Web3 | Decentralized internet on blockchain — users own their data and assets |
| IDRBT | RBI’s banking technology research arm — studies blockchain for Indian banking |
| Ethereum The Merge | September 2022 — Switched from PoW to PoS, 99% energy reduction |
GyanDesk — Competitive Exam Cybersecurity & Technology Study Resource
Covers Blockchain Technology for Banking, UPSC, SSC, Railways, RBI, SEBI & all Government Exams · 65+ Interactive MCQs
⚠️ Always check latest RBI/SEBI/Government notifications before your exam — cryptocurrency and CBDC policies evolve rapidly.
© GyanDesk | Study Smart. Revise Fast. Score High.
Covers Blockchain Technology for Banking, UPSC, SSC, Railways, RBI, SEBI & all Government Exams · 65+ Interactive MCQs
⚠️ Always check latest RBI/SEBI/Government notifications before your exam — cryptocurrency and CBDC policies evolve rapidly.
© GyanDesk | Study Smart. Revise Fast. Score High.