Blockchain Developer Core Blockchain Data Structures 2

Question 1

In a Merkle tree, what is stored at each leaf node?

Accepted Answer

The hash of an individual transaction

Answer

Leaf nodes contain the hashes of individual transactions, which are then combined upward to form the Merkle root.

Question 2

What property of cryptographic hash functions ensures a tiny input change produces a completely different output?

Accepted Answer

The avalanche effect

Answer

The avalanche effect means a single-bit input change cascades into a drastically different hash output.

Question 3

How does a block reference the block before it in the chain?

Accepted Answer

By including the previous block's hash in its header

Answer

Each block header contains the hash of the previous block, creating an immutable cryptographic link.

Question 4

What is the primary benefit of a Merkle tree for lightweight (SPV) clients?

Accepted Answer

They can verify a transaction's inclusion without downloading the full block

Answer

Merkle proofs let SPV clients confirm a transaction belongs to a block using only a small branch of hashes.

Question 5

If a Merkle tree has an odd number of leaf nodes, how is this commonly handled in Bitcoin?

Accepted Answer

The last hash is duplicated to make a pair

Answer

Bitcoin duplicates the final hash when a level has an odd count so it can be paired and hashed.

Blockchain Practice Test