Merkle Tree-Based Transaction Verification BDC Practice Questions (Page 7)

Questions 31–35

1. 31expert · hard

   A developer is implementing a Merkle tree for a block with 3 transactions. The developer wants to ensure that the tree is balanced and follows standard practice. What is the correct root derivation?

   • AHash the first two leaves, then hash that result with the hash of the third leaf duplicated
   • BHash all three leaves together in a single operation
   • CUse the hash of the third leaf as the root
   • DHash the first leaf with the second, and the second with the third, then hash the two results
   Reveal Solution Discussion Select an answer first
2. 32foundation · easy

   Why are transactions hashed individually before being placed into a Merkle tree?

   • ATo compress the transactions so that the block size is reduced.
   • BTo sort the transactions in a deterministic order.
   • CTo create fixed-size representations of transactions that can be combined to form the tree.
   • DTo encrypt the transactions so that only authorized parties can read them.
   Reveal Solution Discussion Select an answer first
4. 33application · medium

   A light client receives a Merkle proof for transaction T. The proof contains the transaction hash and the following sibling hashes: S1 (the sibling of T's leaf), S2 (the sibling of the parent node), and S3 (the sibling of the grandparent node). The client also knows the Merkle root from the block header. What is the correct sequence of operations to verify the proof?

   • AHash S1 with S2, then hash the result with S3, then hash that with T, and compare to the root
   • BHash T with S1, then hash the result with S2, then hash that result with S3, and compare the final hash to the root
   • CHash all four hashes together and compare to the root
   • DCompare T directly to the root
   Reveal Solution Discussion Select an answer first
5. 34foundation · easy

   What is a Merkle path (or authentication path) for a specific transaction?

   • AThe sequence of hashes from the root to the leaf, including the leaf itself.
   • BThe list of all transaction hashes in the block.
   • CThe hash of the transaction itself.
   • DThe list of sibling hashes needed to recompute the root from the transaction's leaf hash.
   Reveal Solution Discussion Select an answer first
6. 35expert · medium

   A blockchain network is considering replacing the Merkle tree with a simple concatenation of all transaction hashes stored in the block header. Which property would be lost?

   • AThe ability to detect tampering of any transaction.
   • BThe ability to verify a single transaction without downloading the entire block.
   • CThe ability to prove the block's proof-of-work.
   • DThe ability to store the block header in a fixed size.
   Reveal Solution Discussion Select an answer first