Free Certified Blockchain Professional (CBCP) Questions and Answers — Questions and Answers

Question 1: What benefit does a public blockchain offer?

Its networks are built by for-profit companies and the working of the network is guaranteed.
It is open to everyone in the world without permission and licensing requirements. (Correct answer)
It is more resilient against fraud, because it uses federated nodes to combat fraud.
It does not use disinterested third parties to secure blocks, as all participants have a vested interest.

Correct answer: It is open to everyone in the world without permission and licensing requirements.

A public blockchain is characterized by its permissionless nature, meaning anyone can join the network, participate in transactions, and validate blocks without needing special authorization or licenses. This openness fosters transparency, decentralization, and broad participation, making it highly resilient to censorship and control by any single entity.

Question 2: What exactly is a blockchain?

A standalone database with history of all transactions on various nodes.
A distributed database with a record of all transactions on the network. (Correct answer)
A client-server database existing on a limited number of nodes at the same time.
A centralized database that holds a subset of all transactions on all nodes.

Correct answer: A distributed database with a record of all transactions on the network.

A blockchain is fundamentally a distributed ledger technology (DLT) that functions as a decentralized database. It maintains a continuously growing list of records, called blocks, which are linked and secured using cryptography. Each block contains a timestamp and transaction data, and once recorded, the data in any given block cannot be altered retroactively without alteration of all subsequent blocks, making it a secure and immutable record of all network transactions.

Question 3: What role does a lightweight node play in a blockchain network?

It verifies transactions by piggybacking on the work of full nodes. (Correct answer)
It stores purchased cryptocurrency for users of a blockchain network.
It stores a complete history of every transaction on the network.
None of the above

Correct answer: It verifies transactions by piggybacking on the work of full nodes.

A lightweight node, also known as a Simple Payment Verification (SPV) client, does not store the entire blockchain history. Instead, it relies on full nodes to provide proof of transactions by downloading only block headers and Merkle proofs. This allows lightweight nodes to verify the validity of transactions with minimal storage and computational resources, making them suitable for mobile devices or users who don't need to run a full node.

Question 4: What does not classify a node?

Miner node
Merkle node (Correct answer)
Lightweight node
Full node

Correct answer: Merkle node

In blockchain terminology, nodes are typically classified by their function, such as 'Full nodes' (which store the entire blockchain), 'Lightweight nodes' (which store only block headers), and 'Miner nodes' (which create new blocks). A 'Merkle node' is not a classification of a node type; rather, a Merkle tree is a data structure used within blocks to efficiently summarize and verify transaction data.

Question 5: A bearer instrument that can be used to transfer value between two parties over a blockchain network. What exactly is this instrument?

A token (Correct answer)
A DApp
A hash
A node

Correct answer: A token

A 'token' on a blockchain is a digital asset that represents a unit of value or utility and can be transferred between parties on the network. Unlike cryptocurrencies which often have their own native blockchain, tokens are typically built on existing blockchain platforms (like Ethereum) and can represent anything from digital currency to ownership of real-world assets or access rights to a service.

Question 6: What distinguishing feature distinguishes a public blockchain?

Allowing anyone to participate in the blockchain network (Correct answer)
Allowing a user to elect nodes to process transactions
Allowing only trusted parties to operate their blockchain
Allowing control over who can participate and at what level

Correct answer: Allowing anyone to participate in the blockchain network

Public blockchains are fundamentally open and permissionless networks, meaning anyone can join, participate in consensus, and validate transactions without needing specific authorization. This inclusive nature is their defining characteristic, fostering decentralization and transparency. It contrasts sharply with private or hybrid blockchains that restrict participation to known or trusted entities.

Question 7: What is an illustration of cryptography being used in a blockchain?

Securing transfers of cryptocurrency between recipients (Correct answer)
Keeping blockchains secure from 51% attacks by corrupt nodes
Creating cryptocurrency as a reward for mining nodes
Accessing private or hybrid blockchains by using a private key

Correct answer: Securing transfers of cryptocurrency between recipients

Cryptography is essential for securing transactions on a blockchain, particularly through the use of public-key cryptography. It ensures that only the legitimate owner of a private key can authorize the transfer of their cryptocurrency. This cryptographic security guarantees the integrity, authenticity, and immutability of every transaction, making trustless transfers of digital assets possible.

Question 8: How do blockchains employ private and public-key cryptography?

Symmetric encryption allows a sender to transfer cryptocurrency to another user. The recipient can then access their funds when the sender grants access to their private key.
The algorithm in the blockchain encrypts and stores private and public keys to all user's wallets. The user then accesses their funds through their twenty-word passphrase key.
In public-key cryptography, one key is used to encrypt and decrypt transaction. The sender uses this key to send cryptocurrency and the recipient’s wallet holds it after decryption.
Asymmetric encryption allows a sender to transfer cryptocurrency to a public key. The recipient can then access these funds with their private key and hold it in their wallet. (Correct answer)

Correct answer: Asymmetric encryption allows a sender to transfer cryptocurrency to a public key. The recipient can then access these funds with their private key and hold it in their wallet.

Blockchains utilize asymmetric (public-key) encryption, where each user has a pair of keys: a public key and a private key. When a sender wants to transfer cryptocurrency, they use the recipient's public key to 'lock' the transaction. The recipient then uses their unique private key to 'unlock' and access these funds, proving ownership without ever exposing the private key itself.

Question 9: How do hybrid blockchain networks defend against 51% attacks?

Through Merkle tree roots, that allow the network to restore itself to its last valid block (Correct answer)
Through incentivization, where miners receive currency for securing the network
Through a Proof of Work (PoW) algorithm, which allows miners to secure the network
Through a central controller ensuring the security of each node in the network

Correct answer: Through Merkle tree roots, that allow the network to restore itself to its last valid block

Hybrid blockchains can defend against 51% attacks by leveraging cryptographic structures like Merkle trees. Each block's transactions are summarized into a single Merkle root hash, which is included in the block header. If an attacker attempts to alter past transactions, the Merkle root would change, allowing the network to detect the inconsistency and revert to the last valid, uncompromised block, thus restoring integrity.

Question 10: How do blockchains work like ledgers?

They periodically update all balances of each wallet to the blockchain.
They hold vast amounts of transaction data as a centralized database.
They hold a record of all transactions that have ever occurred on a network. (Correct answer)
None of the above

Correct answer: They hold a record of all transactions that have ever occurred on a network.

Blockchains function as distributed digital ledgers by maintaining an immutable and chronological record of every transaction that has ever occurred on the network. Each 'block' contains a batch of verified transactions, and these blocks are cryptographically linked together to form a continuous chain. This creates a transparent and tamper-proof history of all activities, accessible to all participants.

Question 11: What are miners' duties in a blockchain network?

Miners compete for a reward by trying to calculate the nonce.
Miners determine the consensus rules that should be followed and interfere when these rules are broken.
Miners act as a single third party to aggregate records and provide trust in the network by the miners’ authority.
Miners are nodes that compete for a reward by calculating the correct nonce to make a transaction possible. (Correct answer)
Miners are computers that allow access to the blockchain, ensuring the number of corrupt nodes will stay low.

Correct answer: Miners are nodes that compete for a reward by calculating the correct nonce to make a transaction possible.

In a Proof of Work (PoW) blockchain, miners are specialized nodes that compete to validate transactions and add new blocks to the chain. Their primary duty involves solving a complex computational puzzle by calculating the correct 'nonce' value. The first miner to successfully find this nonce earns a reward in cryptocurrency and transaction fees, incentivizing them to secure the network.

Question 12: What consensus algorithm is this?

Proof of Burn
Delegated Proof of Stake (DPoS)
Proof of Work (PoW)
Proof of Stake (PoS) (Correct answer)

Correct answer: Proof of Stake (PoS)

Proof of Stake (PoS) is a consensus algorithm where validators are chosen to create new blocks based on the amount of cryptocurrency they 'stake' as collateral. Instead of expending computational power like in Proof of Work, PoS incentivizes honest behavior by requiring participants to lock up their assets. This mechanism secures the network by making it economically unfeasible for malicious actors to attack the chain, as they would risk losing their staked funds.

Question 13: Which consensus algorithm uses the least energy?

Proof of Work (PoW) (Correct answer)
Proof of Space (PoSpace)
Proof of Authority (PoA)
Delegated Proof of Stake (DPoS)

Correct answer: Proof of Work (PoW)

Proof of Work (PoW) is a consensus algorithm that secures the blockchain by requiring miners to expend significant computational effort to solve a cryptographic puzzle. While PoW is fundamental to the security of many robust, decentralized networks, it is widely recognized as the most energy-intensive among common consensus mechanisms. Other algorithms like Proof of Stake (PoS) and Proof of Authority (PoA) are generally designed to be far more energy-efficient.

Question 14: What benefit does Proof of Elapsed Time (PoET) offer over Proof of Work (PoW) as the consensus algorithm?

PoET is usually faster than PoW, because fewer nodes compete for validation than in PoW, since PoET randomly selects the nodes. (Correct answer)
PoET is much more secure than PoW, because PoET supports the trusted execution environment (TEE) by time-stamping the transactions.
PoET has generally lower transaction costs than PoW, because the hardware needed is more generic than the hardware needed for PoW.
PoET can often be used in a permissionless blockchain more easily than PoW, because PoET’s lottery system for node selection is secure.

Correct answer: PoET is usually faster than PoW, because fewer nodes compete for validation than in PoW, since PoET randomly selects the nodes.

Proof of Elapsed Time (PoET) offers a benefit over Proof of Work (PoW) by using a trusted execution environment (TEE) to randomly select a validator after a verifiable waiting period. This eliminates the intense computational competition inherent in PoW, leading to significantly lower energy consumption. Consequently, PoET can achieve faster block finality and higher transaction throughput because fewer nodes are competing for validation.

Question 15: To be able to spend a token or cryptocurrency twice, an attacker tries to alter the blockchain's transaction history. What action by this attacker is most likely to have been taken?

The attacker hard-forked the network and created a new blockchain network.
The attacker gained control of more than 51% of the network’s computing power. (Correct answer)
The attacker edited the smart contract and recovered investor’s cryptocurrency.
The attacker changed the transaction on his node and propagated it in the network.

Correct answer: The attacker gained control of more than 51% of the network’s computing power.

To double-spend a token or cryptocurrency, an attacker must gain control of more than 51% of the network's computing power, known as a 51% attack. With this majority control, the attacker can effectively manipulate the order of transactions and reverse their own confirmed transactions. This allows them to spend the same funds twice by rewriting the blockchain's history to their advantage.

Question 16: Blockchain networks are susceptible to 51% attacks. Which network would provide the greatest incentive for hackers to compromise the system?

Ripple
Bitcoin (Correct answer)
Fabric
None of the above

Correct answer: Bitcoin

Bitcoin, as the largest and most valuable cryptocurrency network, presents the greatest financial incentive for hackers to attempt a 51% attack. The immense value of the network means that successfully double-spending or disrupting transactions could yield substantial profits for an attacker. While achieving 51% control requires significant resources, the potential rewards in Bitcoin's ecosystem are commensurately high.

Free Certified Blockchain Professional (CBCP) Questions and Answers

What benefit does a public blockchain offer?