28:43 For those who are not getting the same result when using online sha256 tools, the echo command is adding a newline character to the output, so the text isn't just what is in the quotes. If you write his command using echo -n, you will get the same result as online tools.
I'm wondering the following about "useful proof of work": Isn't the entire point of proof of work to attach an economic cost to mining? Mining costs electricity and the miner is compensated through the coinbase transaction. That makes complying with the network a net positive operation but makes misbehaving very expensive. If proof of work had some secondary use, the miner could "sell" the result of that computation making the mining process less costly which would defeat the purpose. What am I missing?
1:11:35 Did he just compare the energy wastage of bitcoin mining to the colonial exploitation of precious metals like that was a defense??? Am I crazy???
Question: all a 51 percent attacker would need to do would be to do his fraudulent transaction and rewrite the chain for a few blocks. After that all the other nodes would pick up from his longest chains. Correct? Meaning he wouldnt need to have 51 percent of the computing power forever- rather just long enough so that the rest of the network goes with it... is that right?
That's correct, after the fork becomes accepted, you could drop your compute power. There's no need to hold on, unless there's an adversarial party trying to fork you too :) On the notion of "holding on for few blocks": Do note that 51% only makes you marginally faster, and that it is still a stochastic process. Your next malignly placed fork might just happen to be one of those blocks that take an hour to compute while the benign people get a few lucky blocks, then you need to catch up with that with only a marginal speed difference. So there's still a reasonable chance that targeting the replacement of even a recent block requires pushing your own fork alone for many blocks, when the edge over the rest is that small. Of course, an attacked could get lucky too, and with a little more luck, they could succeed at a reorg even at
For 100 blocks. There's a maturity period before a block producer gets paid for their Proof of Work. So they'd have to win 100 more blocks without the network orphaning them.
I'm losing my mind here trying to replicate the hash at 28:59 online with a basic sha256 online tool and getting a completely different hash output... am i missing something?
I love the slides. They are easy to read, no distracting graphics, and the dark background doesn't burn my eyes watching it at night. You can tell he's a programmer with slides like these.
28:43 For those who are not getting the same result when using online sha256 tools, the echo command is adding a newline character to the output, so the text isn't just what is in the quotes. If you write his command using echo -n, you will get the same result as online tools.
I'm wondering the following about "useful proof of work": Isn't the entire point of proof of work to attach an economic cost to mining? Mining costs electricity and the miner is compensated through the coinbase transaction. That makes complying with the network a net positive operation but makes misbehaving very expensive. If proof of work had some secondary use, the miner could "sell" the result of that computation making the mining process less costly which would defeat the purpose. What am I missing?
I think you summarized it right.
Great lecture series so far!
59:00 hello from 2021. not CAN. it DOES affect markets.
Lol. The change in contrast (49:06) when he says "Got the money... got the money. Oh shoot I don't have the money any more"
Haha
This is all equivocation to me!
Why?
Neha is epic! Learned a ton! Thank you :)
1:11:35 Did he just compare the energy wastage of bitcoin mining to the colonial exploitation of precious metals like that was a defense??? Am I crazy???
Great Lecture !!! THANK YOU!
Great lecture thank you for posting !
22:23 A time traveler wearing a mask on the first row in audience 😱
Certain places have had a culture of wearing a mask while sick for some time before covid. Now we've all learned!
@@alexandermurphy60 it's a joke dude, nothing serious !!!
@@alexandermurphy60 lol so stupid
The dramatic zoom at 1:11:21
*chef's kiss*
This course is amazing!
The electricity usage is a pro
Need more technical analysis of cryptocurrency and blockchain technology
Did anyone understand the synchronous and the asynchronous part of the byzantine tolerance system?
[ Doubt asked by a member of the audience ]
14:00
Great explanation!
Can someone better explain to me (or give me a link) why submitting only close hashes but never a good one is a sneaky attack? (1:21:30). Thank you :)
it's called a BWH attack
1:17:00 quoted NBC as having 110 employees in stl. New year's sighing off.
This was pretty good
Hello.... Its great lesson but you didn't discuss from where the zero date get the output cycle to enroll for the first boot class sector..?!!!
Question: all a 51 percent attacker would need to do would be to do his fraudulent transaction and rewrite the chain for a few blocks. After that all the other nodes would pick up from his longest chains. Correct? Meaning he wouldnt need to have 51 percent of the computing power forever- rather just long enough so that the rest of the network goes with it... is that right?
That's correct, after the fork becomes accepted, you could drop your compute power. There's no need to hold on, unless there's an adversarial party trying to fork you too :)
On the notion of "holding on for few blocks": Do note that 51% only makes you marginally faster, and that it is still a stochastic process. Your next malignly placed fork might just happen to be one of those blocks that take an hour to compute while the benign people get a few lucky blocks, then you need to catch up with that with only a marginal speed difference. So there's still a reasonable chance that targeting the replacement of even a recent block requires pushing your own fork alone for many blocks, when the edge over the rest is that small. Of course, an attacked could get lucky too, and with a little more luck, they could succeed at a reorg even at
For 100 blocks. There's a maturity period before a block producer gets paid for their Proof of Work. So they'd have to win 100 more blocks without the network orphaning them.
Does anyone have a video showing how did they do the homework? Seems a bit difficult for me.
28:32 how is 8 zeros 4 bytes. What are the 4 bytes he is referring to?
In hex format, each number represent 4 bits. Starts from 0 and ends with F. Therefore, 8 zeros represent 32 bits = 4 bytes.
awesome
I'm losing my mind here trying to replicate the hash at 28:59 online with a basic sha256 online tool and getting a completely different hash output... am i missing something?
Same issue trying to replicate the examples of first lecture. Don’t match using sha256.
On his mac, it is inserting a newline. If you put -n in the echo command to strip the newline, you will get the same result as online tools.
I wish the lady did the entire lecture, she is much more easy to follow.
Tadge 14:45
Poisson or Exponential?
@@josephvanname3377 Right. The slide said Poisson, however, it gives the average time to produce the next block. 10 min.
not clear
PoW deanonymises nodes on a public network by design
Neha Narula keeps reusing unlicensed imagery 😂
You know MIT is full of precursor when one of the students at the front of the classroom uses a face mask in 2019
1:54 how the hell did that guy in cap wore a mask in Spring 2018 ...when covid outbreak happened in Jan2020 in U.S.
error in the matrix....
Someone reply to this comment in june 2021 and ask me how my life is going.
how life
@@kamashioh4236 I feel like you should probably learn how to tell time before watching a lecture series from MIT on cryptocurrencies.
@@thethreeheadedmonkey ahahhah
@@thethreeheadedmonkey maybe the hash he's using got it all wrong? lol
Since now nothing going good 😞
Its all worthless now.
Awful slides.
I love the slides. They are easy to read, no distracting graphics, and the dark background doesn't burn my eyes watching it at night. You can tell he's a programmer with slides like these.