1. What is a permissioned blockchain?
a) A blockchain where anyone can join and participate
b) A blockchain where access and participation are restricted to authorized entities
c) A blockchain without any consensus mechanism
d) A blockchain only accessible to government authorities
Answer: b) A blockchain where access and participation are restricted to authorized entities
Explanation: In a permissioned blockchain, access and participation are restricted to certain entities or individuals, typically chosen by the governing authority or consortium.
2. What are some common use cases for permissioned blockchains?
a) Supply chain management
b) Healthcare records management
c) Financial transactions between banks
d) All of the above
Answer: d) All of the above
Explanation: Permissioned blockchains are often utilized in various industries including supply chain management, healthcare, and finance due to their ability to maintain privacy, control, and compliance.
3. Which of the following is NOT a design issue for permissioned blockchains?
a) Scalability
b) Security
c) Anonymity
d) Governance
Answer: c) Anonymity
Explanation: Anonymity is typically not a design issue for permissioned blockchains since participants are usually identified and authenticated.
4. How are contracts executed in permissioned blockchains?
a) Automatically by the network
b) Manually by participants
c) Through smart contracts
d) By the central authority
Answer: c) Through smart contracts
Explanation: Smart contracts are self-executing contracts with the terms of the agreement directly written into code. They automatically execute and enforce the terms upon the occurrence of predefined conditions.
5. What is state machine replication in permissioned blockchains?
a) The process of synchronizing the state of multiple nodes in the network
b) Replicating the entire blockchain ledger on every node
c) Replicating the state of only certain nodes
d) None of the above
Answer: a) The process of synchronizing the state of multiple nodes in the network
Explanation: State machine replication ensures that all nodes in a permissioned blockchain network reach the same state, ensuring consistency and reliability.
6. Which consensus model is commonly used in permissioned blockchains for distributed consensus in a closed environment?
a) Proof of Work (PoW)
b) Proof of Stake (PoS)
c) Paxos
d) Byzantine Generals Problem
Answer: c) Paxos
Explanation: Paxos is a commonly used consensus model in permissioned blockchains for achieving distributed consensus in a closed environment.
7. What is the primary goal of the Paxos consensus algorithm?
a) Achieving scalability
b) Achieving high energy efficiency
c) Achieving fault tolerance
d) Achieving anonymity
Answer: c) Achieving fault tolerance
Explanation: The primary goal of the Paxos consensus algorithm is to achieve fault tolerance, ensuring the system can continue to operate correctly even if some nodes fail or act maliciously.
8. Which consensus model focuses on electing a leader among nodes to propose the next block in the blockchain?
a) RAFT Consensus
b) Byzantine Generals Problem
c) Lamport-Shostak-Pease BFT Algorithm
d) BFT over Asynchronous systems
Answer: a) RAFT Consensus
Explanation: RAFT Consensus focuses on electing a leader among nodes to propose the next block in the blockchain, simplifying the process compared to the traditional Byzantine fault tolerance models.
9. What is the Byzantine Generals Problem in the context of distributed systems?
a) The problem of achieving consensus among a group of unreliable nodes
b) The problem of achieving scalability in blockchain networks
c) The problem of securing communication between nodes
d) The problem of achieving anonymity in blockchain transactions
Answer: a) The problem of achieving consensus among a group of unreliable nodes
Explanation: The Byzantine Generals Problem refers to the challenge of achieving consensus among a group of distributed and potentially faulty nodes, where some nodes may act maliciously or fail to deliver messages.
10. What does BFT stand for in the context of consensus algorithms?
a) Blockchain Fault Tolerance
b) Byzantine Fault Tolerance
c) Blockchain Friendly Transactions
d) Byzantine Friendly Transactions
Answer: b) Byzantine Fault Tolerance
Explanation: BFT stands for Byzantine Fault Tolerance, which refers to the ability of a distributed system to operate correctly and reach consensus even if some nodes fail or act maliciously.
11. Which algorithm is commonly associated with achieving Byzantine fault tolerance in distributed systems?
a) Paxos
b) Proof of Work
c) Lamport-Shostak-Pease BFT Algorithm
d) Proof of Authority
Answer: c) Lamport-Shostak-Pease BFT Algorithm
Explanation: The Lamport-Shostak-Pease BFT Algorithm is a well-known algorithm for achieving Byzantine fault tolerance in distributed systems, ensuring the system can operate correctly despite the presence of faulty nodes.
12. What is the primary challenge addressed by BFT over Asynchronous systems?
a) Achieving scalability in large-scale networks
b) Achieving consensus in networks with unpredictable message delays
c) Achieving energy efficiency in blockchain networks
d) Achieving anonymity in blockchain transactions
Answer: b) Achieving consensus in networks with unpredictable message delays
Explanation: BFT over Asynchronous systems focuses on achieving consensus in networks where message delivery times can vary unpredictably, addressing the challenge of achieving reliable consensus despite such uncertainties.
13. In a permissioned blockchain, who has control over determining which entities can participate in the network?
a) Central authority
b) Random selection
c) Proof of Work miners
d) All nodes in the network
Answer: a) Central authority
Explanation: In a permissioned blockchain, access control is typically managed by a central authority or governing body, which decides which entities are allowed to participate in the network.
14. Which of the following is NOT a characteristic of permissioned blockchains?
a) Open participation
b) Restricted access
c) Greater scalability
d) Higher throughput
Answer: a) Open participation
Explanation: Permissioned blockchains are characterized by restricted access, typically managed by a central authority or governing body, unlike permissionless blockchains where participation is open to anyone.
15. What is the primary advantage of using a permissioned blockchain over a permissionless one?
a) Higher security
b) Greater decentralization
c) Improved scalability
d) Enhanced control and privacy
Answer: d) Enhanced control and privacy
Explanation: The primary advantage of using a permissioned blockchain is the enhanced control and privacy it offers, as access is restricted to authorized entities, providing greater control over the network’s operations and data privacy.
16. Which consensus model is known for its simplicity and ease of implementation in permissioned blockchains?
a) Proof of Work (PoW)
b) Proof of Stake (PoS)
c) Paxos
d) RAFT Consensus
Answer: d) RAFT Consensus
Explanation: RAFT Consensus is known for its simplicity and ease of implementation, making it suitable for permissioned blockchains where network participants are known and trusted.
17. In permissioned blockchains, what role does the central authority typically play?
a) Mining new blocks
b) Validating transactions
c) Managing access control
d) Consensus mechanism
Answer: c) Managing access control
Explanation: In permissioned blockchains, the central authority typically manages access control, deciding which entities are allowed to participate in the network and under what conditions.
18. Which consensus model is based on the principle of achieving agreement through repeated rounds of communication and negotiation?
a) Paxos
b) Byzantine Generals Problem
c) Lamport-Shostak-Pease BFT Algorithm
d) RAFT Consensus
Answer: a) Paxos
Explanation: Paxos consensus is based on the principle of achieving agreement through repeated rounds of communication and negotiation among network nodes, ultimately reaching a consensus on the next block to be added to the blockchain.
19. What distinguishes Byzantine fault tolerance from other consensus mechanisms?
a) It relies on computational puzzles for block validation.
b) It can tolerate a certain number of faulty or malicious nodes.
c) It requires permission from a central authority to participate.
d) It guarantees complete anonymity of participants.
Answer: b) It can tolerate a certain number of faulty or malicious nodes.
Explanation: Byzantine fault tolerance allows a distributed system to tolerate a certain number of faulty or malicious nodes while still maintaining consensus and correct operation.
20. What is the primary drawback of using permissioned blockchains compared to permissionless ones?
a) Lower security
b) Limited scalability
c) Higher costs
d) Reduced decentralization
Answer: d) Reduced decentralization
Explanation: The primary drawback of using permissioned blockchains is the reduced decentralization compared to permissionless ones, as access control is typically managed by a central authority rather than distributed among all participants.