Andrew's Exercise Solutions: BitCoin

Showing posts with label BitCoin. Show all posts

Thursday, January 14, 2016

Bitcoin and Cryptocurrency Technologies Index

Friday, October 23, 2015

Bitcoin and Cryptocurrency Technologies - Quiz 11 Problem 4

According to the lecture, what are some issues with using cryptography to enforce contracts? (check all that apply)

Losing a device containing your private keys could result in the inability to use your smart property	Correct
It is problematic if the state does not recognize a block chain based notion of property because the state will always be the final arbiter	Correct
Cryptographic security lacks the corrective controls of real-world security such as prosecution of criminals	Correct
The technology behind smart contracts is not powerful enough to express the logic needed for real-world contracts like derivatives	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 11 Problem 3

Data feeds.... (check all that apply)

can be decentralized to a degree using multisignatures	Correct
are useful for implementing decentralized prediction markets	Correct
allow arbiters to assert facts about the world into the block chain	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 11 Problem 2

Which of these are potential ways to improve security when using Bitcoin as a platform for decentralized commerce? (check all that apply)

Escrow and dispute mediation	Correct
Warranties	Wrong
Atomic exchange	Correct
Reputation	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 11 Problem 1

In the smart property scenario presented, where Alice sells her car to Bob via an atomic transaction:

Requires modifications to Bitcoin because there is no way for two different people who don't trust each other to securely sign the same transaction	Wrong
Alice and Bob must be physically near the car for the transfer of control to take effect	Wrong
Bob must make sure that Alice deletes her private key so that she does not retain the ability to activate the car	Wrong
The protocol doesn't prove to Bob, before the sale, that the transaction output that Alice wants to sell him actually corresponds to the car he wants to buy	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 10 Problem 3

Here are several ways in which new coins in an altcoin can be allocated to users. Which of these require changes to Bitcoin?

Altcoin allocation is "grandfathered" from Bitcoin - every owner of bitcoins becomes the owner of a certain number of altcoins (in a fixed proportion of bitcoins to altcoins)	Wrong
All coins in the altcoin are generated through (merge) mining and are allocated to miners	Wrong
Bitcoin is used as a "reserve currency" for the altcoin - a unit of the altcoin can be created by putting 1 BTC into escrow; the bitcoin can be released by provably destroying one altcoin unit	Correct
A unit of the altcoin is created by provably destroying one bitcoin	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 10 Problem 2

In a merge-mined altcoin scenario:

Bitcoin blocks include transactions from the altcoin	Wrong
Bitcoin block headers include the merkle root of transactions for an altcoin block	Correct
Altcoin block headers include a hash pointer to a Bitcoin block	Wrong
The altcoin has the same hash target as Bitcoin at all times	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 10 Problem 1

Which of these statements about altcoins are true? (check all that apply)

Bitcoin is the most widely forked cryptocurrency	Wrong
Bitcoin has a higher "market capitalization" than all altcoins combined	Correct
Namecoin supports additional functionality such as domain-name registration that is not found in Bitcoin	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 9 Problem 5

In a prediction market where shares pay out if and only if a potential future event happens: (check all that apply)

The average price of all shares traded as a fraction of the payout is an estimate of the event's likelihood	Wrong
A trader who is able to control or influence the outcome of the event will likely be able to make a profit	Correct
The current price of shares as a fraction of the payout is an estimate of the event's likelihood	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 9 Problem 4

Which of these are advantages of using the Bitcoin blockchain to generate a cryptographic beacon? (check all that apply)

The beacon outputs random bits at frequent intervals	Correct
No central authority is needed	Correct
Fresh random bits can be obtained at any desired future time	Wrong
The cost to an attacker to manipulate the beacon's output is quantifiable	Correct
Manipulating the beacon output requires 51% mining power	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 9 Problem 3

Which of the following features does the Bitcoin secure multi-party lottery system presented depend on? (check all that apply)

Multisignatures	Correct
Colored coins	Wrong
Time-locked transactions	Correct
Hash commitments	Correct
Micropayments	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 9 Problem 2

The OpenAssets protocol works by

Forking Bitcoin to allow many different types of "colored" coins	Wrong
Enabling conversion between Bitcoin and a new type of coin	Wrong
Associating extra metadata with bitcoins	Correct
Exploiting non-fungibility of bitcoins to impose a blacklist	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 9 Problem 1

In which of these situations could secure timestamping be useful? Assume that there is no way to prove that you didn’t timestamp multiple values

Proving possession of a document at a specific time	Correct
Proving that you can predict the winner of the 2016 US presidential election	Wrong
Securely saving a document at a specific time	Wrong
Proving that you don't know something at a specific time	Wrong

Monday, October 5, 2015

Bitcoin and Cryptocurrency Technologies - Quiz 8 Problem 4

Which of these is true of virtual mining? (check all that apply)

Virtual mining does away with most of the power requirements of proof-of-work systems	Correct
Several variations of virtual mining have been proposed	Correct
A proof-of-stake system makes 51% attacks impossible	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 8 Problem 3

In a vigilante attack against a mining pool, the attacker...

discards both shares and blocks that he finds	Wrong
submits shares but discards blocks	Correct
discards shares while submitting blocks to a different mining pool	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 8 Problem 2

Proof-of-useful-work cryptocurrency designs... (check all that apply)

differ from traditional volunteer distributed computing projects because cryptocurrencies cannot rely on a trusted administrator to select and distribute the problems to be solved	Correct
should preferably be based on problems whose solution benefits the public, rather than the solver, to avoid skewing the incentives of miners	Correct
have been successfully used to solve computational problems such as protein folding	Wrong

Bitcoin and Cryptocurrency Technologies - Quiz 8 Problem 1

ASIC resistance... (check all that apply)

is a response to the centralization of Bitcoin mining	Correct
has been successfully achieved in practice using the scrypt memory-hard hash function	Wrong
seeks to make it more appealing to mine with regular consumer devices than it is today	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 7 Problem 6

Which of these are signs that there might be a market failure? (check all that apply)

Customers are unable to tell the difference between high-quality and low-quality products	Correct
Sellers agree with each other to raise prices	Correct
The market is completely unregulated	Wrong
Sellers agree not to compete with each other and offer a reduced selection of products	Correct

In fact, unregulated market means market success, it can manage itself!

Bitcoin and Cryptocurrency Technologies - Quiz 7 Problem 5

A reputation-based approach to fixing a lemons market might not work: (check all that apply)

When consumers don't do repeat business with the same entity	Correct
When sellers don't provide warranties for products	Wrong
At the end of a sellers presence in the market	Correct
At the beginning of a sellers presence in the market	Correct

Bitcoin and Cryptocurrency Technologies - Quiz 7 Problem 4

According to the lecture, what steps do governments take to prevent money laundering? (check all that apply)

Require a variety of companies to file reports describing any large transactions they are a party to	Correct
Constantly monitor the Bitcoin network and block chain	Wrong
Limit the maximum size of financial transactions	Wrong
Require some businesses that handle money to know their customers identities	Correct