Blockchain Test 1 — Questions and Answers
Question 1: Which of the following are real-world Blockchain applications?
- A video sharing website
- Voting
- Identity management
- All of the above (Correct answer)
Correct answer: All of the above
Explanation: <br> The blockchain is a logical technological advancement that is also philosophically progressive, as it transfers power and control of essential information from CEO boards to the general public. If blockchain technology can be developed and expanded to the required degree, it has the potential to eliminate corporate fraud and abuse of power.
Question 2: On a public Blockchain, who can read the records?
- No one
- Everyone on the Blockchain (Correct answer)
- The users with access permissions
- Only the creator
Correct answer: Everyone on the Blockchain
Explanation: <br> On a public blockchain network, anyone can read, write, and see data. It is impossible to change or delete an entry once it has been confirmed in a public blockchain. Permissioned blockchains are private blockchains.
Question 3: A block header is made up of which item(s)?
- The hash of the previous block (Correct answer)
- The time stamp of the block and the genesis block hash
- The hash of every transaction in a specific block and the next block
- The hash of the Merkle root and the header of the previous block
Correct answer: The hash of the previous block
The correct answer: <br> The hash of the previous block
Question 4: What happens if two blocks are confirmed simultaneously?
- Both chains are removed from the pool, and the unconfirmed transactions are re-added.
- The Orderer Block verifies which block has the most transactions confirmed.
- The blocks are broken up into two chains. Each chain is then extended by adding blocks until it reaches its maximum length. The Blockchain is therefore defined as the longest chain.
- Which block is added to the Blockchain is decided by the nodes. (Correct answer)
Correct answer: Which block is added to the Blockchain is decided by the nodes.
Explanation: <br> The chain will split if more than one block is validated at the same time. In other words, each node in a blockchain keeps a copy of the database. Let's pretend that two blocks, A and B, were certified at the same moment. After both blocks have been validated, some nodes will receive A first, while others will receive B first.
Question 5: For cryptocurrencies, which of the following challenges did Blockchain solve?
- Double Spending
- Destination of currencies
- Anonymity (Correct answer)
- None of the above
Correct answer: Anonymity
Explanation: <br> The fundamental difficulty is that the anonymity-provisioning mechanism must allow other members to verify updates to the blockchain. Most blockchain-based e-cash protocols' pseudonymous feature is insufficient for users to achieve identification and transaction privacy.
Question 6: Which of the following attacks requires only a single account and only uses standard blockchain operations?
- 51% Attack
- Replay Attack (Correct answer)
- Eclipse Attack
- Routing Attack
Correct answer: Replay Attack
Explanation: <br> A replay attack can only make an identical transaction in the old blockchain by copying an existing transaction from the new forked blockchain (or the other way around). Remember that transactions received without sufficient replay protection can be replayed months or even years later.
Question 7: Which of the following methods for generating pseudo-random numbers for smart contracts is recommended?
- Block hashes
- Private variables
- External oracle (Correct answer)
- Private functions
Correct answer: External oracle
The correct answer: <br> External oracle
Question 8: Which of the following biockchains has an architectural design that is channel-focused?
- Ethereum
- Hyperledger (Correct answer)
- Corda
- None of the above
Correct answer: Hyperledger
Explanation: <br> Hyperledger is an open source collaborative initiative aimed at advancing blockchain technologies across industries. The Linux Foundation hosts a global partnership that includes professionals in finance, banking, the Internet of Things, supply chains, manufacturing, and technology.
Question 9: What is one typical way for "chaining" pieces of data together in sequence in a blockchain design?
- Writing each block into a separate file on the hard disk of the node
- Store the hash of the previous block within the current block (Correct answer)
- Assigning an order number to each block so they can be sorted when requested
- Having the genesis node store an ordered, mutable array of block hashes
Correct answer: Store the hash of the previous block within the current block
The correct answer: <br> Store the hash of the previous block within the current block
Blockchain Test 1
Which of the following are real-world Blockchain applications?