Blockchain Security Training Fundamentals of Blockchain Security 2 — Questions and Answers
Question 1: What is the primary security purpose of a cryptographic hash function in a blockchain?
- To encrypt user wallet passwords
- To produce a fixed-length, tamper-evident fingerprint of block data (Correct answer)
- To compress block data for faster transfer
- To randomly assign mining rewards
Correct answer: To produce a fixed-length, tamper-evident fingerprint of block data
Hash functions create a deterministic, fixed-length fingerprint so any change to block data is immediately detectable.
Question 2: How does each block in a blockchain link to the previous one?
- By storing the previous block's hash in its header (Correct answer)
- By copying the previous block's full transaction list
- By sharing the same timestamp
- By using the same miner's address
Correct answer: By storing the previous block's hash in its header
Each block stores the previous block's hash, creating an immutable chain where altering one block breaks all subsequent links.
Question 3: Which property ensures that a blockchain transaction cannot be denied by its sender?
- Confidentiality
- Non-repudiation via digital signatures (Correct answer)
- Availability
- Anonymity
Correct answer: Non-repudiation via digital signatures
Digital signatures prove the sender authorized the transaction, providing non-repudiation.
Question 4: What does a 51% attack allow a malicious actor to do?
- Steal private keys from any wallet
- Control consensus to double-spend or reorganize the chain (Correct answer)
- Decrypt all on-chain data
- Mint unlimited new tokens from thin air
Correct answer: Control consensus to double-spend or reorganize the chain
Controlling a majority of hashing or staking power lets an attacker rewrite recent history and double-spend.
Question 5: Why is a private key the most critical secret in blockchain security?
- It is needed to view public balances
- It authorizes spending and proves ownership of funds (Correct answer)
- It encrypts the entire blockchain
- It is required to run a full node
Correct answer: It authorizes spending and proves ownership of funds
Whoever holds the private key can sign transactions and control the associated assets.
Question 6: What is the security advantage of decentralization in a blockchain network?
- It eliminates the need for cryptography
- It removes a single point of failure or control (Correct answer)
- It makes transactions reversible
- It hides all transaction amounts
Correct answer: It removes a single point of failure or control
Distributing the ledger across many nodes means no single party can be compromised to control or halt the network.
Question 7: Which statement best describes blockchain immutability?
- Data can never be read once written
- Confirmed records are practically impossible to alter without detection (Correct answer)
- Only administrators can change records
- Records expire after a set time
Correct answer: Confirmed records are practically impossible to alter without detection
Immutability means confirmed entries cannot be changed without redoing all subsequent proof-of-work and being detected.
Blockchain Security Training Fundamentals of Blockchain Security 2
What is the primary security purpose of a cryptographic hash function in a blockchain?