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Exam Preparation
Question 1. Which component of the Ethereum architecture is responsible for executing smart contract bytecode? A) Ethereum Consensus Layer B) Ethereum Virtual Machine C) Peer-to-Peer Network Layer D) Transaction Pool Answer: B Explanation: The Ethereum Virtual Machine (EVM) interprets and runs the compiled bytecode of smart contracts, providing a sandboxed execution environment. **Question 2. In the context of the blockchain trilemma, which combination is most often sacrificed to achieve high throughput in a permissioned network like Quorum? ** A) Security and Decentralization B) Scalability and Security C) Decentralization and Scalability D) All three are equally preserved Answer: A Explanation: Permissioned networks trade some decentralization (fewer, known validators) to gain security and scalability, enabling higher transaction rates. Question 3. What cryptographic hash function does Ethereum use for generating addresses and transaction hashes? A) SHA- 256 B) RIPEMD- 160
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C) Keccak- 256 D) Blake2b Answer: C Explanation: Ethereum employs Keccak-256 (the pre-standardized version of SHA-3) for hashing data such as transaction contents and contract code. Question 4. Which type of Ethereum account can hold code and maintain its own storage? A) Externally Owned Account (EOA) B) Contract Account C) Validator Account D) Miner Account Answer: B Explanation: Contract Accounts store compiled bytecode and a persistent state, whereas EOAs are simple key-pair holders without code. Question 5. In Quorum, what is the primary purpose of the Tessera (formerly Constellation) component? A) Mining new blocks using PoW B) Managing private transaction payloads and encryption C) Providing a public JSON-RPC endpoint D) Synchronizing node clocks Answer: B
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A) Transactions are rejected by the network. B) Nodes must still pay fees in Ether. C) Transactions incur no cost, as gas is not charged in permissioned settings. D) Gas is automatically doubled to compensate. Answer: C Explanation: In permissioned Quorum networks, gas fees are often disabled or set to zero because participants are known and the network does not rely on fee incentives. Question 9. Which file in a Quorum node configuration defines the list of nodes that are allowed to connect to the network? A) genesis.json B) permissioned-nodes.json C) static-nodes.json D) network-id Answer: B Explanation: permissioned-nodes.json contains the enode URLs of authorized peers, enforcing node-level permissioning. Question 10. In IBFT, what is the purpose of the “prepare” phase? A) Leader proposes a block hash. B) Validators broadcast their signatures on the proposed block. C) Validators verify that they have received the same block and send a prepare message. D) Final commitment of the block to the chain.
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Answer: C Explanation: During the prepare phase, each validator confirms receipt of the same block and broadcasts a prepare message, moving toward consensus. Question 11. Which Solidity pragma version is recommended for maximum compatibility with the latest Quorum releases? A) pragma solidity ^0.4.24; B) pragma solidity ^0.5.0; C) pragma solidity ^0.6.12; D) pragma solidity ^0.8.0; Answer: D Explanation: Quorum’s underlying EVM supports Solidity 0.8.x, offering safety features like overflow checks while remaining fully compatible. Question 12. When deploying a private smart contract on Quorum, which additional parameter must be supplied to the deployment transaction? A) gasLimit B) privateFor C) value D) chainId Answer: B Explanation: The privateFor parameter specifies the recipient nodes that should receive the private contract’s code, ensuring confidentiality.
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C) All pending transactions are discarded. D) The network switches to IBFT automatically. Answer: B Explanation: Raft includes a leader election mechanism; when the current leader fails, followers trigger an election to choose a new leader. Question 16. Which of the following is NOT a responsibility of the Tessera enclave? A) Generating asymmetric key pairs for encryption. B) Storing encrypted transaction payloads. C) Validating consensus algorithm votes. D) Managing secure communication between nodes. Answer: C Explanation: Consensus validation is handled by the consensus engine (Raft or IBFT), not by Tessera, which focuses on privacy and encryption. Question 17. How does Quorum achieve high transaction throughput compared to public Ethereum? A) By increasing block size to 10 MB. B) By eliminating the need for gas and using faster consensus algorithms. C) By running on a proof-of-stake network. D) By using a sharding mechanism. Answer: B
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Explanation: Quorum removes gas fees and adopts efficient consensus (Raft/IBFT), reducing latency and enabling higher TPS. Question 18. Which command-line flag enables a Quorum node to run with the IBFT consensus engine? A) --raft B) --ibft C) --consensus ibft2 D) --dev Answer: C Explanation: The flag --consensus ibft2 tells the client to start the Istanbul BFT consensus algorithm. Question 19. In the context of account permissioning, what does the term “whitelisting” refer to? A) Blocking all incoming connections. B) Allowing only pre-approved accounts to send transactions. C) Giving all accounts unrestricted access. D) Automatically approving any transaction from unknown accounts. Answer: B Explanation: Whitelisting restricts transaction creation to a set of approved accounts, enhancing security in permissioned networks. Question 20. Which tool can be used to quickly spin up a multi-node Quorum network with Docker containers?
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Answer: C Explanation: Quorum adds a privateStateRoot to the block header, representing the private state trie for parties involved in private transactions. Question 23. What is the default block time for a Raft-based Quorum network? A) 1 second B) 5 seconds C) 15 seconds D) Variable, based on leader heartbeat Answer: D Explanation: Raft’s block time is driven by the leader’s heartbeat interval and can be tuned; there is no fixed default like in PoW networks. Question 24. Which of the following best describes “on-chain permissioning” in Quorum? A) Permission checks performed by an external firewall. B) Storing whitelist/blacklist data in a smart contract that enforces access rules. C) Using a centralized database for node authentication. D) Relying solely on TLS certificates. Answer: B Explanation: On-chain permissioning uses smart contracts to store and enforce rules about which accounts or nodes may interact with the network.
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Question 25. In a Quorum network using IBFT, how many faulty nodes can the system tolerate while still reaching consensus in a network of 7 validators? A) 1 B) 2 C) 3 D) 4 Answer: B Explanation: IBFT tolerates f = (n-1)/3 Byzantine faults. For n = 7, f = 2, meaning up to two malicious validators can be tolerated. Question 26. Which of the following is a primary benefit of using Docker Compose with Quorum Wizard? A) Automatic generation of Solidity source code. B) Simplified orchestration of multiple nodes, Tessera instances, and networking. C) Real-time gas price monitoring. D) Integration with public Ethereum mainnet. Answer: B Explanation: Docker Compose defines services for each node and its Tessera enclave, allowing coordinated startup and teardown. Question 27. What does the privacyGroupId field represent in a Quorum private transaction? A) The hash of the transaction receipt. B) An identifier for a set of participants that share a private state. C. The public address of the sender.
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Explanation: Hardhat’s network config can include a privateFor array specifying recipient public keys, enabling deployment of private contracts. Question 30. Which monitoring tool is commonly paired with Prometheus to visualize Quorum node metrics? A) Kibana B) Grafana C) Splunk D) Nagios Answer: B Explanation: Grafana reads metrics from Prometheus and provides dashboards for visualizing node performance, block rates, and consensus health. Question 31. In Quorum, what is the purpose of the txPool? A) Storing encrypted private payloads. B) Managing pending public transactions before they are included in a block. C) Holding the list of validator nodes. D) Generating cryptographic keys for accounts. Answer: B Explanation: The transaction pool (txPool) queues public transactions awaiting inclusion in the next block; private payloads are handled separately by Tessera. Question 32. Which of the following best describes “crash-fault tolerance” (CFT) as provided by Raft? A) The ability to tolerate malicious nodes that send conflicting messages.
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B) The ability to continue operating despite a subset of nodes unexpectedly stopping. C) The ability to prevent double-spending attacks. D) The ability to process transactions without any latency. Answer: B Explanation: CFT ensures the system remains functional when some nodes crash or become unreachable, assuming they do not act maliciously. Question 33. Which Solidity modifier is recommended to restrict a function to only authorized accounts in a permissioned Quorum network? A) onlyOwner from OpenZeppelin B) payable C) view D) pure Answer: A Explanation: onlyOwner (or a custom access-control modifier) enforces that only designated accounts can invoke sensitive functions, aligning with permissioned requirements. Question 34. In the context of Quorum, what does the term “public transaction” refer to? A) A transaction whose payload is encrypted. B) A transaction that is visible to all nodes and stored in the public state. C) A transaction that requires a gas fee. D) A transaction that can only be executed by validators.
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Question 37. When deploying a contract to a Quorum network, why might a developer set the gas limit to a very high value? A) To ensure the transaction never runs out of gas because gas is not charged. B) To increase the transaction’s priority over others. C) To trigger a special discount on the network fee. D) To enable the contract to run on the public Ethereum mainnet. Answer: A Explanation: In permissioned Quorum, gas is not deducted, but the EVM still checks that the supplied gas limit is sufficient; setting a high limit prevents out-of-gas errors. Question 38. Which of the following best explains the purpose of the “pre-prepare” phase in IBFT? A) Validators vote on the next leader. B) The proposer broadcasts the block hash and prepares the commit. C) Nodes synchronize their clocks. D) The network finalizes the block without further messages. Answer: B Explanation: In the pre-prepare phase, the proposer (leader) sends the block hash to all validators, initiating the three-phase commit process. Question 39. Which command is used to generate a new Tessera key pair for a node? A) geth account new B) tessera generatekeys
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C) openssl ecparam -genkey D) quorum-node create Answer: B Explanation: Tessera provides a generatekeys utility to create the asymmetric key pair used for encrypting private payloads. Question 40. In Quorum, what does the term “private state” refer to? A) The state of the public blockchain after private transactions are omitted. B) A separate Merkle-Patricia trie that stores contract storage visible only to authorized participants. C) The memory cache of a node’s JVM. D) The list of all private keys stored on a node. Answer: B Explanation: Private state is maintained in a distinct trie whose root is stored in the block header, ensuring confidentiality for private contracts. Question 41. Which of the following is NOT a recommended practice when writing Solidity contracts for Quorum? A) Using require statements for input validation. B) Hard-coding private keys inside the contract. C) Emitting events for important state changes. D) Keeping functions pure or view when no state modification is needed. Answer: B
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A) It specifies the gas price for the transaction. B) It identifies the sender’s Tessera public key, enabling recipients to verify the origin. C) It determines the block number where the transaction will be placed. D) It sets the maximum block size. Answer: B Explanation: privateFrom contains the sender’s Tessera public key, allowing the receiving Tessera nodes to locate and decrypt the payload. Question 45. In a Quorum network, which component is responsible for ordering transactions before they are included in a block? A) Tessera B) Consensus Engine (Raft or IBFT) C) Transaction Pool (txPool) D) Smart Contract VM Answer: B Explanation: The consensus engine determines the order of transactions and assembles them into blocks. Question 46. Which of the following best describes “off-chain permissioning”? A) Storing permission data in a smart contract on the blockchain. B) Managing node and account access through external systems such as LDAP or certificate authorities. C) Using a separate blockchain to handle permissions. D) Relying on miners to enforce rules.
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Answer: B Explanation: Off-chain permissioning uses external identity management tools to control who can join or transact, without storing rules on the ledger. Question 47. What is the purpose of the --rpcapi flag when starting a Quorum node? A) To specify which APIs are exposed over the JSON-RPC interface, such as eth, quorum, and txpool. B) To set the maximum gas limit per block. C) To define the consensus algorithm. D) To enable TLS encryption for RPC calls. Answer: A Explanation: --rpcapi lists the RPC modules the node will expose, allowing clients to interact with the appropriate Quorum-specific endpoints. Question 48. Which of the following is a characteristic of a “privacy group” in Quorum? A) It is automatically created for every public transaction. B) Its membership can be dynamic, allowing nodes to be added or removed via on-chain transactions. C) It requires a minimum of ten participants. D) It only exists in Raft-based networks. Answer: B Explanation: Privacy groups can be managed on-chain, enabling flexible addition or removal of participants while preserving private state.
