Blockchain Developer Core Blockchain Data Structures Questions and Answers

Question 1

What is the primary advantage of organizing transactions within a block into a Merkle tree instead of a simple list?

Accepted Answer

It enables efficient and secure verification of a transaction's inclusion without needing the entire block's transaction data.

Answer

It determines the chronological order in which transactions are executed by the virtual machine.

Answer

It allows for the encryption of sensitive transaction data before it is added to the block.

Answer

It significantly reduces the on-chain storage size of the transactions themselves.

Question 2

A block header in a blockchain contains several key pieces of data to summarize the block. Which of the following is typically found in the block's *body* rather than its header?

Accepted Answer

The complete list of individual transactions

Answer

The hash of the previous block's header

Answer

The nonce used in the mining process

Answer

The Merkle root of the block's transactions

Question 3

An attacker attempts to alter the amount of a single transaction within a previously confirmed block (e.g., Block #500) on a public blockchain. What is the most direct and immediate cryptographic consequence of this action?

Accepted Answer

The Merkle root stored in the header of Block #500 will no longer be valid.

Answer

The timestamp of the next block (Block #501) will be automatically invalidated by all nodes.

Answer

The private keys of the transaction's original participants are immediately compromised.

Answer

The nonce of Block #500 will need to be recalculated by the network.

Question 4

In an account-based blockchain like Ethereum, what is the primary purpose of the 'State Trie' (also known as the World State Trie)?

Accepted Answer

To provide a data structure that maps every account address to its corresponding state, including its balance, nonce, and storage.

Answer

To store the complete history of every transaction ever executed on the network.

Answer

To exclusively track the total supply and issuance schedule of the native cryptocurrency.

Answer

To organize all transaction receipts for a given block in a verifiable manner.

Question 5

The integrity of the chain of blocks relies on cryptographic hash functions. Which property of these functions is most critical for preventing an attacker from finding two different sets of block data that result in the exact same block hash?

Accepted Answer

Collision Resistance

Answer

Determinism

Answer

Pre-image Resistance

Answer

Fast Computation

Question 6

Which of the following statements best describes the relationship between transactions, the Merkle root, and the block header?

Accepted Answer

Individual transactions are hashed to form a Merkle tree, and the root hash of this tree is included in the block header.

Answer

The Merkle root is a hash of the previous block's header and is stored within each transaction.

Answer

Each transaction contains the Merkle root, which is then hashed along with the previous block's header.

Answer

The block header contains all individual transactions, which are then used to calculate the Merkle root.