Blockchain Bootcamp Quiz 01

What is an advantage of a public blockchain?

• It does not use disinterested third parties to secure blocks, as all participants have a vested interest.

• It is more resilient against fraud, because it uses federated nodes to combat fraud.

• It is open to everyone in the world without permission and licensing requirements.

• Its networks are built by for-profit companies and the working of the network is guaranteed.

What is a blockchain?

• A centralized database that holds a subset of all transactions on all nodes.

• A client-server database existing on a limited number of nodes at the same time.

• A distributed database with a record of all transactions on the network.

• A standalone database with history of all transactions on various nodes.

What is a key characteristic of a public blockchain?

• Allowing a user to elect nodes to process transactions

• Allowing anyone to participate in the blockchain network

• Allowing control over who can participate and at what level

• Allowing only trusted parties to operate their blockchain

What is an example of the use of cryptography in a blockchain?

• Accessing private or hybrid blockchains by using a private key

• Creating cryptocurrency as a reward for mining nodes

• Keeping blockchains secure from 51% attacks by corrupt nodes

• Securing transfers of cryptocurrency between recipients

How do blockchains function like ledgers?

• They hold a record of all transactions that have ever occurred on a network.

• They hold vast amounts of transaction data as a centralized database.

• They periodically update all balances of each wallet to the blockchain.

What is the task of miners in a blockchain network?

• Miners act as a single third party to aggregate records and provide trust in the network by the miners’ authority.

• Miners are computers that allow access to the blockchain, ensuring the number of corrupt nodes will stay low.

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

• Miners determine the consensus rules that should be followed and interfere when these rules are broken.

Which description fits only the Proof of Work (PoW) consensus algorithm?

• A collaborative consensus algorithm, where approved accounts do the validation.

• A collaborative consensus algorithm that is facilitated by farmers, who offer leftover memory of theircomputer to make transactions possible.

• A consensus algorithm, where the validation is done for the entire transaction flow, including not only the correctness, but also the sequence of transactions.

• A low-cost and fast algorithm, where a node needs to deposit cryptocurrency to guarantee the transaction.

• An intensive and expensive, competitive algorithm where each mining node on the blockchain is competing to secure blocks.

An attacker tries to corrupt the transaction history of a blockchain to be able to spend a token or a cryptocurrency twice.

What is the most likely thing this attacker did?

• The attacker changed the transaction on his node and propagated it in the network.

• The attacker edited the smart contract and recovered investor’s cryptocurrency.

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

• The attacker hard-forked the network and created a new blockchain network.

Which characteristic of a blockchain network is also its protection?

• The greater the number of full independent nodes, the harder it is to compromise the data in the blockchain.

• The lower the number of miners in the blockchain, the higher the incentive is for securing the network

• The more centralized the control of the blockchain is, the harder it is to secure the data and avoidfraud.

• The more complicated the Proof of Work (PoW) algorithm is, the more rewarding it is to secure the network.

How can information be secured in a blockchain?

• By using a closed peer-to-peer (P2P) network, sharing information across platforms

• By using a distribution of cryptocurrencies over miners through the network

• By using asymmetric cryptography, consisting of a public and private key

• By using distributed ledger technology (DLT), which records transactions at the source