Blockchain Security Training Fundamentals of Blockchain Security 3 — Questions and Answers
Question 1: In public-key cryptography used by blockchains, which key is shared openly?
- The private key
- The public key (Correct answer)
- The seed phrase
- The signing nonce
Correct answer: The public key
The public key (or derived address) is shared so others can verify signatures and send funds.
Question 2: What is a Sybil attack in a blockchain network?
- Flooding the network with fake identities to gain disproportionate influence (Correct answer)
- Breaking the hash function with quantum computers
- Stealing a private key through phishing
- Overheating mining hardware
Correct answer: Flooding the network with fake identities to gain disproportionate influence
A Sybil attack uses many fake nodes or identities to subvert reputation or consensus systems.
Question 3: How does Proof of Work deter attacks on a blockchain?
- By requiring attackers to expend large computational resources (Correct answer)
- By encrypting all transactions twice
- By hiding miner identities
- By limiting block size to 1 MB
Correct answer: By requiring attackers to expend large computational resources
PoW makes attacks economically costly because rewriting history requires enormous computing power.
Question 4: What is the main security trade-off of storing assets in a hot wallet?
- It cannot sign transactions
- It is internet-connected and more exposed to remote attacks (Correct answer)
- It loses funds after 30 days
- It requires no private key
Correct answer: It is internet-connected and more exposed to remote attacks
Hot wallets stay online for convenience but their connectivity increases exposure to hacking.
Question 5: Which of the following is a key benefit of a cold storage wallet?
- Faster transaction confirmation
- Private keys kept offline, away from network attacks (Correct answer)
- No need for a private key at all
- Automatic recovery of lost funds
Correct answer: Private keys kept offline, away from network attacks
Cold storage keeps keys offline, drastically reducing the attack surface for remote theft.
Question 6: What does a digital signature verify about a blockchain transaction?
- The transaction fee is correct
- The sender authorized it and the message was not altered (Correct answer)
- The block timestamp is accurate
- The recipient is online
Correct answer: The sender authorized it and the message was not altered
A signature confirms both authenticity of the sender and integrity of the signed data.
Question 7: Why are seed phrases considered highly sensitive in wallet security?
- They only display balances
- They can regenerate all private keys and restore full wallet access (Correct answer)
- They are required to broadcast blocks
- They expire and must be renewed
Correct answer: They can regenerate all private keys and restore full wallet access
A seed phrase deterministically recreates every private key in a wallet, so anyone with it controls the funds.
Blockchain Security Training Fundamentals of Blockchain Security 3
In public-key cryptography used by blockchains, which key is shared openly?