Bitcoin - Proof of work

An explanation of cryptographic proof-of-work protocols, which are used in various cryptographic applications and in bitcoin mining.

Video by Zulfikar Ramzan. Zulfikar Ramzan is a world-leading expert in computer security and cryptography and is currently the Chief Scientist at Sourcefire. He received his Ph.D. in computer science from MIT.

[zulfikarramzan]

This answer is spot on. Traditional digital cash schemes solved the double spending problem by having a centralized (online) entity that could check for coins being spent repeatedly. Bitcoin provides a nifty solution that works without a centralized entity by leveraging the proof of work. As long as honest nodes control the majority of the collective computing power, it's an uphill battle for a dishonest node to successfully double spend. Instead, they are better off mining themselves.

[Mattc]

This is a very easy to understand video that I will be recommending to people.

[bitcoinbrisbane]

Yep. But there was a good article on read on this. Lets say an avalon miner runs at 60ghs and costs $1, 500. BTC guild which do half of all mining is currently pooled at 35, 757 ghs. So assume total is 2x this. So cost of creating a competing node would be $1, 500x1000 or lets round up to $2m. Current value of BTC is ~$100m. $2m gamble, but do able.

[illyushen]

I didn't understand what problem it solves? apart from having a structured hash output? is it worth spending so much energy just to get the hash of desired pattern? Am I missing something here?

[Sagricon]

Nice...but there are some other explanations needed e.g. who would be creating a challenge for miners to solve the puzzle and then who would be validating the outcome.

[sickle]

In bitcoin, what is the challenge part and who validates it? What prevents a miner from just randomly generating a string with the correct number of zeros?

[main___name___main___name]

It's still possible to hear bits of what is being said. You should speak more softly, or better, mute the microphone to ensure nothing gets through to the audience.

[zulfikarramzan]

The intent was more to provide a detailed explanation of the mechanics of bitcoin since it's a question on many peoples' minds. Whether it's safe to put your money in bitcoins is an entirely different question. There are definitely many risks in doing so!

[patrik]

Volume is crazy low. Maybe increase it a bit?

[docsein]

I have a question. It'd be great if someone can explain.

It seems like this whole process depends on the hash function (both the proof of work, and validation). If an hash function is just an algorithm, or a mathematical formula, then one can work backwards as well as forwards.

What's stopping someone from finding out the hash algorithm and working backwards to find a valid hash code without working through the 1 trillion inputs?

[yandaox]

Easiest video to understand in YouTube for proof of work!

[yellowlght]

God you for this priceless education - without these videos this member of the general public would be completely lost - you should seriously consider putting all of this information into a book format -

[element]

5:20 No need to reiterate portions of what you were building up to say. That confuses a typical person trying to understand every detail. In fact, the video editor should have cut that out, or replaced it -- with you restating a more clear message.

[CRIresearch]

I love this bitcoin series. Very helpful.

[JimSowers]

This video would be a lot more valuable if you walked through an actual example, start to finish. You say 'for example', but then still work on a theoretical level (e.g. first 40 bits are 0). Show an example with actual data as to what it would look like on a website to how the calculations would be done, and how you would pick/create a challenge.

[ftb_official]

Why to use n-number of leading zeros? Why exactly zeros?

[giladbaruchian]

who decides what is the challenge ?
does it change from block to block? how?

thanks

[David-lypr]

Ótimo! Obrigado ao tradutor que traduziu este vídeo para português!

[carlosdebourbondeparme]

how does the "sever" know for certain that there even is a solution for its challenge?

[harshrajjadeja]

one suggestion, get your content on some page before starting the video, because when you take uncertain breaks in speaking, that disturbs the viewers link of understanding