Blockchain CBSA Practice Test - Questions Answers, Page 6
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Question 51

The block creation time is set to how many minutes in Bitcoin?
Explanation:
Remember, that the block creation time is set to 10 minutes and this can never change. So after a fixed time of approximately 2 weeks or exactly 2016 blocks the difficulty is re-adjusted. Increase in difficulty means target decreases.
Reference: https://medium.com/all-things-ledger/decoding-the-enigma-of-bitcoin-mining-f8b2697bc4e2
Question 52

In Hyperledger Fabric chaincode runs in a secured Docker container isolated from the endorsing peer process?
Explanation:
Reference: http://hyperledger-fabric.readthedocs.io/en/release-1.1/chaincode.html
Question 53

You would like to run Ethereum DApps in a browser without a node. (No need to download blockchain.) What could you use locally in your Chrome browser?
Explanation:
Metamask is essentially a bridge.
Question 54

You would like to start your Gethin Fast Sync Mode.
What is the command for this?
Explanation:
Reference: https://datawookie.netlify.com/blog/2018/01/ethereum-running-a-node/
Question 55

Which of the following is not considered an Ethereum testnet?
Question 56

Looking the graph below, what type of an attack is this likely?
Explanation:
A proof of work system is vulnerable to a particular type of attack called the "P+ epsilon attack". In order to understand how this attack works we must define some terms before hand. Un-Coordinated Choice Model: An uncoordinated choice model is a model where all the participants don't have the incentive to work with one another. The participants may form groups but at no time is the group big enough to become a majority.
Reference: https://blockgeeks.com/guides/hypothetical-attacks-on-cryptocurrencies/
Question 57

What does the 20 in ERC20 mean or relate to?
Explanation:
ERC stands for Ethereum Request for Comments. This is an official protocol for proposing improvements to the Ethereum network. '20' is the unique proposal ID number.
Reference: https://support.exodus.io/article/108-what-is-an-erc20-token-and-does-exodus-support-it
Question 58

You are considering writing a smart contract for Ethereum and would like to use a robust programming language. Which programming language is considered the most flexible and robust for Ethereum?
Explanation:
To write smart contracts there are a few different languages: Solidity, which is like JavaScript and has .sol as a file extension, Serpent, Python-like with extension .se, and a 3rd, LLL, based on Lisp. Serpent was popular a while back but Solidity is the most popular right now and more robust, so just use Solidity. You prefer Python? Use Solidity.
Reference: https://medium.com/@ConsenSys/a-101-noob-intro-to-programming-smart-contracts-on-ethereum-695d15c1dab4
Question 59

How many peers in the network need to endorse a transaction in a Hyperledger Fabric blockchain?
Explanation:
The number of peers required to endorse a transaction is driven by the endorsement policy that is specified at chaincode deployment time.
Reference: http://hyperledger-fabric.readthedocs.io/en/release-1.1/Fabric-FAQ.html#endorsement
Question 60

Every node needs to keep track of time AND it needs to be in synch with its other peer nodes on the blockchain. In Bitcoin for example the current median for time is around?
Explanation:
The median time differs by more than 70 mins from its system time
Reference: https://blockgeeks.com/guides/hypothetical-attacks-on-cryptocurrencies/
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