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This quiz will check your understanding of Lecture 2.

In accordance with the Coursera Honor Code, I (Anonymous Student) certify that the answers here are my own work.

Question 1

Which of these factors make distributed consensus hard? (check all that apply)

Nodes may crash

Nodes may be taken over by malware

Encrypted messages may be intercepted and decrypted

There is latency on the network

Question 2

Why is Bitcoin able to reach consensus in practice despite this being a generally difficult problem? (check all that apply)

Financial incentives cause participants to work together

Only small groups of nodes have to reach consensus rather than the network having to globally reach consensus

The order of blocks doesn’t matter for consensus

Consensus only has to be reached over long time scales

Question 3

What can a malicious node do? (check all that apply)

Prevent a valid transaction from getting any confirmations

Ignore the longest valid branch rule when proposing a new block

Create valid transactions originating from someone else’s address

Question 4

Proof of work is a way to: (check all that apply)

Let nodes compete for the “right” to create blocks

Make it impossible for one miner to act like many different miners

Select nodes in proportion to computing power

Question 5

A block in the block chain was found at time t. What is the probability that the next block was found at or before time t + 10 minutes? Assume that the total hash power of the network stays constant. (select all that apply)

More than 50%

Less than 50%

Exactly 50%

Question 6

A 51% attacker can potentially

Steal coins from an existing address

Make it unprofitable for other miners to mine

Change the block reward

Suppress transactions from the block chain

Question 7

Which of the following are true?

51% attacks are difficult because an adversary would need to control more than half of the nodes on the Bitcoin network

Proof-of-work is essential for preventing sybil attacks on the Bitcoin blockchain

As a transaction gets buried deeper in the blockchain, it becomes less and less likely that it will ever be undone because the work required to make a longer alternate branch becomes more and more difficult

In accordance with the Coursera Honor Code, I (Anonymous Student) certify that the answers here are my own work.

You cannot submit your work until you agree to the Honor Code. Thanks!

Bitcoin and Cryptocurrency Technologies

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Bitcoin and Cryptocurrency Technologies

Bitcoin and Cryptocurrency Technologiesby Arvind Narayanan

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Bitcoin and Cryptocurrency Technologies
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