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Lecture 21: Bitcoin

预习

Bitcoin: A Peer-to-Peer Electronic Cash Syste

FAQ

  1. I don't understand why the blockchain is so important. Isn't the requirement for the owner's signature on each transaction enough to prevent bitcoins from being stolen?
  2. Why does Bitcoin need to define a new currency? Wouldn't it be more convenient to use an existing currency like dollars?
  3. Why is the purpose of proof-of-work?
  4. Could a Bitcoin-like system use something less wasteful than proof-of-work?
  5. Can Alice spend the same coin twice by sending "pay Bob" and "pay Charlie" to different subsets of miners?
  6. It takes an average of 10 minutes for a Bitcoin block to be validated. Does this mean that the parties involved aren't sure if the transaction really happened until 10 minutes later?
  7. What can be done to speed up transactions on the blockchain?
  8. The entire blockchain needs to be downloaded before a node can participate in the network. Won't that take an impractically long time as the blockchain grows?
  9. Is it feasible for an attacker to gain a majority of the computing power among peers?
  10. Are there any ways for Bitcoin mining to do useful work, beyond simply brute-force calculating SHA-256 hashes?
  11. There is hardware specifically designed to mine Bitcoin. How does this type of hardware differ from the type of hardware in a laptop?
  12. The paper estimates that the disk space required to store the block chain will by 4.2 megabytes per year. That seems very low!
  13. Would the advent of quantum computing break the bitcoin system?
  14. Bitcoin uses the hash of the transaction record to identify the transaction, so it can be named in future transactions. Is this guaranteed to lead to unique IDs?
  15. It sounds like anyone can create new Bitcoins. Why is that OK? Won't it lead to forgery or inflation?
  16. The paper mentions that some amount of fraud is admissible; where does this fraud come from?
  17. Has there been fraudulent use of Bitcoin?
  18. Satoshi's paper mentions that each transaction has its own transaction fees that are given to whoever mined the block. Why would a miner not simply try to mine blocks with transactions with the highest transaction fees?
  19. Why would a miner bother including transactions that yield no fee?
  20. How are transaction fees determined/advertised?
  21. What are some techniques for storing my personal bitcoins, in particular the private keys needed to spend my bitcoins? I've heard of people printing out the keys, replicating them on USB, etc. Does a secure online repository exist?
  22. What other kinds of virtual currency were there before and after Bitcoin (I know the paper mentioned hashcash)? What was different about Bitcoin that led it to have more success than its predecessors?
  23. What happens when more (or fewer) people mine Bitcoin?
  24. Is there any way to make Bitcoin completely anonymous?
  25. If I lose the private key(s) associated with the bitcoins I own, how can I get my money back?
  26. What do people buy and sell with bitcoins?
  27. Why is bitcoin illegal in some countries?
  28. Why do bitcoins have any value at all? Why do people accept it as money?
  29. How is the price of Bitcoin determined?
  30. Why is the price of bitcoin so volatile?

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FAQ 答案

[作业](6.824 Spring 2018 Paper Questions.html)