13. Blockchain

Question 1

What is blockchain technology?

Answer 1

A decentralized digital ledger that stores records transparently, immutably, and securely.

Question 2

What is the main purpose of blockchain?

Answer 2

To enable secure transactions without a central authority.

Question 3

What does decentralization mean in blockchain?

Answer 3

No single entity controls the network.

Question 4

What problem does decentralization solve?

Answer 4

Single point of failure.

Question 5

What is transparency in blockchain?

Answer 5

All transactions are visible to participants.

Question 6

What is pseudonymity?

Answer 6

Using public keys instead of real identities.

Question 7

What is immutability?

Answer 7

Transactions cannot be changed after being added.

Question 8

How is immutability achieved?

Answer 8

Through cryptographic hashing.

Question 9

How does blockchain ensure integrity?

Answer 9

By linking blocks with hashes.

Question 10

How does blockchain support availability?

Answer 10

Through distributed nodes.

Question 11

What is a distributed ledger?

Answer 11

A ledger replicated across many nodes.

Question 12

What is fault tolerance?

Answer 12

System continues despite node failures.

Question 13

What is censorship resistance?

Answer 13

No single entity can block transactions.

Question 14

What is a block?

Answer 14

A container of transactions.

Question 15

What are the two main parts of a block?

Answer 15

Header and body.

Question 16

What is stored in a block header?

Answer 16

Previous hash, timestamp, Merkle root, nonce.

Question 17

What is the purpose of previous block hash?

Answer 17

Links blocks and ensures integrity.

Question 18

What is a Merkle root?

Answer 18

Hash of all transactions in a block.

Question 19

What is a Merkle tree?

Answer 19

Binary tree of hashes.

Question 20

Why are Merkle trees used?

Answer 20

Efficient verification of transactions.

Question 21

What is a nonce?

Answer 21

A number used once in mining.

Question 22

What is stored in block body?

Answer 22

List of transactions.

Question 23

What information does a transaction contain?

Answer 23

Sender, receiver, amount, signature.

Question 24

What provides authenticity in transactions?

Answer 24

Digital signatures.

Question 25

What is transaction initiation?

Answer 25

Broadcasting a signed transaction.

Question 26

What do nodes verify?

Answer 26

Signature and balance.

Question 27

What is a mempool?

Answer 27

Pool of pending transactions.

Question 28

What is block creation?

Answer 28

Grouping transactions into a block.

Question 29

Who creates blocks?

Answer 29

Miners or validators.

Question 30

What is a consensus mechanism?

Answer 30

Protocol for agreeing on ledger state.

Question 31

Why is consensus needed?

Answer 31

No central authority.

Question 32

What does consensus ensure?

Answer 32

Integrity, trust, security.

Question 33

What is Proof of Work (PoW)?

Answer 33

Consensus using computational puzzles.

Question 34

What is required in PoW?

Answer 34

Finding a nonce with low hash.

Question 35

Why is PoW secure?

Answer 35

Attacks are expensive.

Question 36

What is a drawback of PoW?

Answer 36

High energy use.

Question 37

What is centralization risk in PoW?

Answer 37

Mining pools dominate.

Question 38

What is Proof of Stake (PoS)?

Answer 38

Consensus based on staked currency.

Question 39

How are validators chosen in PoS?

Answer 39

Based on stake size.

Question 40

Why is PoS energy-efficient?

Answer 40

No heavy computation.

Question 41

What is a drawback of PoS?

Answer 41

Wealth concentration.

Question 42

Name other consensus mechanisms.

Answer 42

DPoS, PoA, PBFT, PoC, PoB, PoET.

Question 43

What happens after consensus?

Answer 43

Block is added to chain.

Question 44

What happens after block addition?

Answer 44

Ledger is updated.

Question 45

When is a transaction confirmed?

Answer 45

After block inclusion.

Question 46

What is a smart contract?

Answer 46

Self-executing code on blockchain.

Question 47

What triggers smart contracts?

Answer 47

Predefined events.

Question 48

What is automation in smart contracts?

Answer 48

Automatic execution.

Question 49

Why are smart contracts irreversible?

Answer 49

They are immutable.

Question 50

What language is used for Ethereum contracts?

Answer 50

Solidity.

Question 51

What is scalability problem?

Answer 51

Low transaction throughput.

Question 52

Why is blockchain slow?

Answer 52

All nodes validate transactions.

Question 53

How many TPS does Bitcoin handle?

Answer 53

About 7 TPS.

Question 54

What causes energy concerns?

Answer 54

Proof of Work mining.

Question 55

Why is immutability a challenge?

Answer 55

Bugs cannot be fixed easily.

Question 56

What is lack of standardization?

Answer 56

Different incompatible platforms.

Question 57

What is regulatory uncertainty?

Answer 57

Unclear legal rules.

Question 58

What is privacy concern?

Answer 58

Public transaction visibility.

Question 59

What is a 51% attack?

Answer 59

Control of majority network power.

Question 60

What can a 51% attacker do?

Answer 60

Rewrite transaction history.

Question 61

How does 51% attack enable double spending?

Answer 61

Creates longer fraudulent chain.

Question 62

What industries use blockchain?

Answer 62

Finance, supply chain, healthcare, government.

Question 63

What is a dApp?

Answer 63

Decentralized application.

Question 64

What is CBDC?

Answer 64

Central Bank Digital Currency.

Question 65

What is the main strength of blockchain?

Answer 65

Decentralized trust.

Question 66

What is the main weakness of blockchain?

Answer 66

Scalability and energy use.

Question 67

What is the future challenge for blockchain?

Answer 67

Overcoming limitations.

Question 68

What is the main exam lesson of blockchain?

Answer 68

Security through decentralization and cryptography.