Fundamental Concepts and Working Principles of Blockchain Technology BBLC Practice Questions (Page 4)

Questions 16–20

1. 16foundation · easy

   What is the primary purpose of a consensus mechanism in a blockchain?

   • ATo allow participants to agree on the valid state of the ledger.
   • BTo encrypt all transactions in the network.
   • CTo store transaction data in a centralized database.
   • DTo provide a user interface for managing blockchain nodes.
   Reveal Solution Discussion Select an answer first
2. 17application · medium

   A developer is explaining to a client how a blockchain ensures that a transaction recorded in block 100 cannot be silently changed without detection. Which explanation is most accurate?

   • ABlock 100 contains a timestamp that is verified by a trusted third party, so any change would be detected.
   • BBlock 101 contains the hash of block 100's header, so any change to block 100 would cause a mismatch when block 101 is validated.
   • CBlock 100 is encrypted with a key that only the original miner possesses, so no one else can modify it.
   • DBlock 100 is stored on a read-only medium, such as a CD-ROM, so it cannot be altered.
   Reveal Solution Discussion Select an answer first
4. 18expert · hard

   A government agency is implementing a blockchain for citizen identity management. They need to balance transparency for audit purposes with privacy for citizens. They also need to ensure that only authorized government entities can issue identity credentials. Which design best achieves this balance?

   • AA consortium blockchain where multiple private companies also have write access, to increase decentralization.
   • BA public blockchain where all identity data is visible to everyone, ensuring maximum transparency.
   • CA permissioned blockchain where authorized government entities can issue credentials, and identity data is stored as hashes or encrypted, with decryption keys held by the citizen and granted to auditors only with consent.
   • DA private blockchain where only the government agency has write access, and all data is visible only to that agency.
   Reveal Solution Discussion Select an answer first
5. 19application · medium

   A supply-chain consortium records shipment events on a private blockchain. An auditor wants to verify that a specific pallet's temperature readings have not been altered since they were recorded. Which property of the blockchain directly enables this verification?

   • AEach block contains a cryptographic hash of the previous block, forming an unbroken chain.
   • BThe blockchain uses a permissioned network where only authorized members can submit transactions.
   • CEach participant maintains a full copy of the ledger, ensuring redundancy of the data.
   • DAll nodes in the consortium must approve every transaction before it is added to the ledger.
   Reveal Solution Discussion Select an answer first
6. 20expert · hard

   A global supply chain consortium is designing a blockchain network. They have three requirements: (1) transactions must finalize in under 2 seconds, (2) the network must remain operational even if up to 3 of the 10 member organizations' nodes fail or act maliciously, and (3) the network should not rely on a single organization for governance. Which consensus mechanism and network type best satisfies all three requirements?

   • AProof of Stake (PoS) on a public blockchain, because it is energy-efficient and allows all stakeholders to participate.
   • BDelegated Proof of Stake (DPoS) on a private blockchain, with a single delegate responsible for block production.
   • CPractical Byzantine Fault Tolerance (PBFT) on a permissioned consortium blockchain, with a validator set of 10 nodes (one per member).
   • DProof of Work (PoW) on a public blockchain, because it provides the highest level of decentralization and security.
   Reveal Solution Discussion Select an answer first