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Ever wonder how Bitcoin (and other cryptocurrencies) actually work?

75999 ratings | 2381934 views
Bitcoin explained from the viewpoint of inventing your own cryptocurrency. Videos like these made possible by patreon: https://patreon.com/3blue1brown Protocol Labs: https://protocol.ai/ Interested in contributing? https://protocol.ai/join/ Special thanks to the following patrons: http://3b1b.co/btc-thanks Some people have asked if this channel accepts contributions in cryptocurrency form as an alternative to Patreon. As you might guess, the answer is yes :). Here are the relevant addresses: ETH: 0x88Fd7a2e9e0E616a5610B8BE5d5090DC6Bd55c25 BTC: 1DV4dhXEVhGELmDnRppADyMcyZgGHnCNJ BCH: qrr82t07zzq5uqgek422s8wwf953jj25c53lqctlnw LTC: LNPY2HEWv8igGckwKrYPbh9yD28XH3sm32 Supplement video: https://youtu.be/S9JGmA5_unY Music by Vincent Rubinetti: https://soundcloud.com/vincerubinetti/heartbeat Here are a few other resources I'd recommend: Original Bitcoin paper: https://bitcoin.org/bitcoin.pdf Block explorer: https://blockexplorer.com/ Blog post by Michael Nielsen: https://goo.gl/BW1RV3 (This is particularly good for understanding the details of what transactions look like, which is something this video did not cover) Video by CuriousInventor: https://youtu.be/Lx9zgZCMqXE Video by Anders Brownworth: https://youtu.be/_160oMzblY8 Ethereum white paper: https://goo.gl/XXZddT If you want to contribute translated subtitles or to help review those that have already been made by others and need approval, you can click the gear icon in the video and go to subtitles/cc, then "add subtitles/cc". I really appreciate those who do this, as it helps make the lessons accessible to more people. Music by Vince Rubinetti: https://vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown ------------------ 3blue1brown is a channel about animating math, in all senses of the word animate. And you know the drill with YouTube, if you want to stay posted on new videos, subscribe, and click the bell to receive notifications (if you're into that). If you are new to this channel and want to see more, a good place to start is this playlist: http://3b1b.co/recommended Various social media stuffs: Website: https://www.3blue1brown.com Twitter: https://twitter.com/3Blue1Brown Patreon: https://patreon.com/3blue1brown Facebook: https://www.facebook.com/3blue1brown Reddit: https://www.reddit.com/r/3Blue1Brown
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Text Comments (3859)
ulf schack (21 hours ago)
Thank you!
JOe-HOs (1 day ago)
what would happen if miners just stopped
SAL (59 minutes ago)
+JOe-HOs there is no way to see the number of individual miners, however, we do know roughly how much total mining power there is. Many miners team up together into mining pools - just googling "bitcoin mining pools" should show the big pools out there.
JOe-HOs (9 hours ago)
SAL thanks, is there a way to see how many miners are currently working
SAL (10 hours ago)
Then transactions would stop getting included in the blockchain. But it would also mean it tons of profit being left up for grabs, which would lead to many people (my self included) to jump into the mining game to get some easy money, and thus mining would resume.
Charles Farrell (1 day ago)
Very informative! Many thanks!
Yusuk [Zebs] (2 days ago)
I'm actually sad that I just found this channel instead of way sooner.
Pranit Bhisade (2 days ago)
Is it possible that you are satoshi nakamoto and you don't want to reveal it..thanks
Yusril Atfan (3 days ago)
QuantumCoin. wow.
rocel Aidoma (6 days ago)
Great video. :)
Elfcheg (9 days ago)
6:09 OBJECTION! 2^256 roughly equals to 10^78. Which is not very much, because our Universe consists of 10^80 elementary particles. And if you want to measure the volume of a Universe in PLank volumes, you will get something like 10^185. So please, do not judge astronomy ;)
Ya Moya (5 days ago)
This is the best video I’ve seen in 2019 so far about what market and BTC price is doing https://youtu.be/oIO13Z0db_M
Pat Black (11 days ago)
Fuck yes, I’m so happy I found this. You gave the best breakdown of a block chain.
Ravish Mahajan (11 days ago)
The best video on blockchain on internet so far
Rodolfo Assereto (12 days ago)
At 19:56, if I were Alice, I would broadcast to everyone the information that Bob payed ME. How do they know I'm lying? Thanks for helping guys
Royal Pro YT (12 days ago)
50 BTC enough to be rich
Semih Özel (16 days ago)
The only thing that i know, is that i know nothing. Thanks 3Blue1Brown
Edo Peter (17 days ago)
Obviously this monetary system is not for rural populace. They would rather stick with the status quo which is void of the necessity to understand all these complexities.
Choco_Jack (17 days ago)
3blue 1crown
Ariyan Ansari (17 days ago)
is it possible to use Fourier transform to seprate the frequencies base on their nodes?
arno cea (19 days ago)
In the spirit of your 2^256 cryptography security video, could you do a follow up on the ecological impact of cryptocurrencies ? My understanding is that all these protocols require an insane amount of energy, and that therefore if we all relied on cryptocurrencies, our impact in term of energy consumption would be colossal.
이홍재 (19 days ago)
i really wonder how do we put money into the pot to prevent someone take it  ??????. Anyway it's so amazing video!!!!!
Joel Barker (20 days ago)
Wouldn't quantum computing, which greatly reduces the work required for procedural attempts, require programs reliant on SHA-256 to find a new method of encryption?
victor dave (21 days ago)
Trade instruments such as 100x perpetuals on a platform built by HFT and Exchange engineers (ex-Nasdaq, ex-NYSE) https://bit.ly/2R6Edu8
LivingBlast, LLC (22 days ago)
3:08 uh... what?
Phoenixツ (22 days ago)
How did I not know about this channel before
Shrike DeCil (23 days ago)
The only question I have is: Why on Earth was the underlying core computation (SHA256) used instead of some provably NP(Hard) computation? That is, we -think- reversing SHA(256) is NP(Hard), but as you stated in the video, it's really "Well, we don't know a way to reverse this."
Victor Popov (23 days ago)
Explain how a DAG works and how it is superior then a block chain. Would like to see Nano mentioned for example and how it achieves instant and no fee transactions.
SAL (23 days ago)
It is extremely unlikely a DAG can be more secure than the Bitcoin blockchain.
leslie sylvan (23 days ago)
Next to quantum physics, crypto-currencies are the most elusive of concepts to fully grasp ;)
64standardtrickyness (24 days ago)
Sorry I find your example at 21:14 confusing how would bob not know whether or not Alice paid him $100??? my understanding is that there is a large database of "miners" that hear all transactions, and thus their ledgers are always the same
SAL (16 days ago)
+64standardtrickyness By fraudulent transactions (or blocks that contain them), I mean they are transactions that are breaking the network consensus rules. Some obvious examples: a transaction that tries to spend bitcoin without providing a digital signature from the private key (ie. spending bitcoins from an account you don't control) or trying to create a transaction that references an x amount of bitcoin but making the output be greater than x (ie. trying to spend more than you have in your account) - these types of situations are not a concern at all as the network instantly disregards those transactions and blocks that may contain them. The only issue left is double spending (which is what I think you are getting at in your example) - if someone has say 1 bitcoin, then makes 2 different transactions referencing that 1 bitcoin. On the face of it, neither transaction on its own is fraudulent, but both can't be true. If two different miners solve competing blocks, but each includes one of the two contradicting transactions, then both branches at that point are still fair game (there is no false block yet), but one branch is abandoned over time as the majority of mining power will choose one branch to build on (it makes no economic sense for a miner to build on a minority/losing branch). Even if a player with large compute power did go through with trying out your example, they would have very likely lost much more than they would have hoped to gain as they wasted valuable time and electrical resources mining the block or blocks they don't want included in the longest blockchain. What it comes down to is this: if you are receiving a large transaction, don't consider it "finalized" until many subsequent blocks have been built on top of the block that contains the transaction of interest, to ensure that you are not being double spent. For example, if i'm receiving 100 bitcoin, I wouldn't trust it after seeing it in only 1 block (I'm not going to immediately send them whatever they paid for just yet) - I can however be confident it is finalized after waiting 6-10 blocks have been built on top of it - someone trying to double spend that transaction to me at that point would not only need to redo that block, but they would also need to solve all the subsequent blocks as well, which would at that point have cost them much more than 100 bitcoin in electrical power to pull off. Miners make money by playing by the rules and building on the longest chain, not by wasting resources on blocks that don't get included in the longest blockchain.
64standardtrickyness (17 days ago)
@SAL by fraudulent block, do you mean the transactions are not verified or something else? My question was in the absence of any central processing system or omnicient miners supposing there was a period of time which an adversary attempting to cheat would have more computing power during that time send someone else 100 bitcoins and then attempt to make a block hiding that transaction (or stating that no such transaction occured I'm not sure if the blocks represent transactions or time but it shouldn't matter) and using their superior computing power at a particular time, quickly output a block hiding their transaction and find the key for that block making their (false) block temporarily the longest and then the other miners come back, see that this person has the longest block and works on this (false ) block
SAL (17 days ago)
+64standardtrickyness if it is indeed a fraudulent block/chain (with an invalid transaction), it simply will not be accepted by the network as they check it in real time (nothing to worry about). However, if it is a competing chain with double spent coins ( coins being spent to 2 different addresses), then all you have to do is sit back and wait for a few more blocks to see which branch the majority of miners are building on (that becomes the true blockchain, since it will gather the most proof of work). That is why it is good practice to wait for 3-6 blocks to be built on any particular block that has a transaction of interest to you. It doesn't matter if a miner gets "lucky" for a few blocks, it is not something that can be kept up continuously.
64standardtrickyness (22 days ago)
but that doesn't fundamentally solve the issue of getting lucky (or putting in power during some downtime) at some point and being able to output the most mining power by one block (by outputting one fradulent block on top of the output previously with most computing power) wouldn't all miners then start working on this fradulent branch hence perpetualting the wrong branch?
SAL (22 days ago)
+64standardtrickyness  To determine which branch is the valid/true blockchain, it is the one with the most mining power put into it. Imagine that you are a miner and you see a completing branch that has less mining power behind it - it would not make sense to go mine on it because the rest of the network won't acknowledge it as valid. Alice in this situation is doomed to lose as the rest of the miners have more mining power than Alice.
a logical human (26 days ago)
But then how will bank charge transaction tax ? Exchange rate will difficult to control if not Impossible . Then if someone government (major power colluding )have super computer which can peta flop computing having larger block can controll all transactions ? Also if you are generating money without any physical work how it will be valued ? How to prevent hawala , money laundering , tax evasion?
SAL (23 days ago)
The idea with Bitcoin is to completely bypass any bank or government control. Exchange rate and value is determined by the free market. If mining is compromised, then the users will upgrade to fix it. You don't need a physical object to value, the Bitcoin blockchain can be run and examined by anyone. You can't stop black market transactions from happening - which now means governments will have to do actual detective work to go after criminals.
J.R. W (26 days ago)
What if Alice says "Bob paid me 100 LD" and broadcast that to everyone? Wouldn't all new miners unknowingly put that in their blockchain? The only conflicting ledger would be Bob's?
SAL (23 days ago)
The transaction will only be included in the blockchain if it is valid, and it is only valid if the transaction from Bob was digitally signed by Bob's private key. I hope that makes sense. Invalid transactions are ignored by the network, and are not included in the blockchain.
MIguel Lopez (27 days ago)
Yes, very clear. By explaining cryptpcurrency in more detail... Your video helps it all make more sense.
Kyle Church (29 days ago)
"You're a programmer, right? If you agree to program my multi-billion dollar idea, I'll give you 0.5%. Brace yourself: Like Facebook, but with blockchain."
Adshayan Balendra (29 days ago)
@t survey about bitcoin
Adshayan Balendra (29 days ago)
@t survey about bitcoin
Adshayan Balendra (29 days ago)
@t survey about bitcoin
phillip woolf (29 days ago)
I just watched an ad about cryptocurrencies while trying to watch a video about cryptocurrencies. How strange is that.
George Salapa (29 days ago)
One of the best and most intelligible explanations I have seen. Thx.
mustafa azyoksul (30 days ago)
I watched this video twice, 14 months apart. It was very confusing to me at the time but now it helped me understand blockchain and cryptocurrencies much better. Difference is crystal clear. I am sad to see 2.3M views for this tresure.
Vorname Nachname (1 month ago)
2:43 I see inappropriate Symbols! XD
dal9 (1 month ago)
Best youtube channel, no cap
Nemo D123 (1 month ago)
In reality Santa's little helpers do all the calculations. They are so busy doing it, that no one will get Xmas presents this year. Also Santa wasted all his money on this years bad trades.
OthmanEmpire (1 month ago)
Thanks for the video =)
John yepthomi (1 month ago)
Bang on. We don't mind you Going into the details at all... Keep it up!! Clear and concise!
Erich Kaltenbrunner (1 month ago)
You can bye a bitcoin miner box that consumes 2 kilowatt of power for about 3000€ and spoons the cream of the milk. Bye bitcoins and loose your money. Or bye one Maschine after the other and a bit more money will get out of it then you have to invest in power bill an hardware. It has already been done. This is a criminal bitcoin commercial.
Sophia Loren (26 days ago)
Electric Scam!
Erich Kaltenbrunner (1 month ago)
Virtual money already did virtually disappear in the billions. Money for idiots and criminals.
Lucas S. Lovén (1 month ago)
Also my first time to finally start understanding how this works. Thank you!
amgee007 (1 month ago)
I love the content and the graphics of all of the 3B1B videos, but something about his voice and the background music lulls me to sleep within a few minutes. It takes several iterations to make it through a video. I appreciate the effort, I just don't know why I can't stay awake.
Shibasis Patel (1 month ago)
I truly can't explain the amount of respect I have for you! I am maintaining a list of incredible persons who helped me in some point of my life for free and you are on the top of that list. I will surely contribute some amount, once I start earning. God bless you! Keep making awesome videos! Love from India.
Toni Kaiser (1 month ago)
Why always Alice and Bob? In every video about cryptovurrencys these names are used, is this an insider?
Toni Kaiser (30 days ago)
+SAL Ok makes sense thank you I have often heart it from Charles Hoskinson. I take this is the same like "hallo world" in every programming language.
SAL (30 days ago)
"Alice and Bob" is the go to example that has been used in computer science for many decades. Kind of like how in algebra is is usually "find X".
Toni Kaiser (1 month ago)
Endlich mal einer der das ganze wirklich grundlegend erkärt und auf die Technologie dahinter eingeht und nicht nur Bitcoin to the Moon, investiert alles rein herumbrüllt...
3bodyZZ (1 month ago)
Proof of work is shit. we need a new better algorithm
SAL (25 days ago)
+Sophia Loren it's worth it.
Sophia Loren (26 days ago)
Carbon Footprint is Insane.
SAL (1 month ago)
All the other 'better' algorithms out there are much less secure.
Mayank sharma (1 month ago)
The blocks which are rejected makes their computational work a waste? And the bitcoins obtained too..?
SAL (1 month ago)
Correct, rejected blocks are totally disregarded.
Stephen dela Cruz (1 month ago)
5:27 Could you please explain how this function Verify(Message, Signature, pk) approximately works? How is it possible to verify whether the appropriate secret key was used using the public key?
miss elfy (1 month ago)
I'm a cryptography student and I think that It's a very complicated concept,I can't believe that this was created by humans.
miss elfy (1 month ago)
Very good video, I admire your channel.I come here everytime I want to understand a topic.Thank you.
GGShinobi77 (1 month ago)
great video! Thank you! And the animated Pi's are super cute! ^^
Tareq Rahman (1 month ago)
this was useful . thanks #3Blue1Brown @3Blue1Brown
Danny Meeks (1 month ago)
What if Alice was a state actor with the state-of-the-art not yet even commercialized algorithmic hashing technology? Maybe not today, but eventually third world dictators are going to have a collection of well-educated computer engineers and software cryptographic engineers who might be capable of designing systems to outpace the current collective of miners.
John (1 month ago)
crypto has been very good to me. - the guy on youtube ' celente branson ' has been deadly accuate with crypto.
Jithin K.S. (1 month ago)
I really appreciate the way how you take a topic that is so complex and break it down as much as possible to make it comprehensible to anyone who has no prior knowledge about the topic...Really appreciate it...
MrBauchnabbel (1 month ago)
"To call it astronomicly large would be giving way too much credit to astonomy." My new favourite quote :)
Rabbit Hole (1 month ago)
I'd love a comment or reply to this comment I am aout to make, because it seems highly relevant to the issue of understanding safety of cryptocurrency's: How about AI? AI could crack any secret code. Any hacker could create a program to hack any attempt at another person's security. In other words, NO crypto currency would or could EVER be safe, as long as AI exists, which it does, and it's not going away either. So. . . . . for that reason alone, this seems entirely implausable, period. In fact, the banks could TOALLY just switch over to this and use AI to manage anyone's currency who does not have access or can use AI to make themselves safe.. . . Seems like they(banks and families in power) could also buy the best hackers alive.
Max G. (1 month ago)
More precisely, you would need to brute force up to: 115792089237316195423570985008687907853269984665640564039457584007913129639936 possible values to crack a sha256 message.
Max G. (1 month ago)
I’m going to assume that you mean a bot instead of AI. If you understand the mathematics behind SHA256, then you would understand why you can’t just “create AI” that cracks a secret code. These aren’t just 4 digit pins on your garage or passwords that people are using to secure the data, having 2^256 possible values is to have more possible values than the number of atoms in the observable universe. It doesn’t matter if you have a bot that can compute millions of codes a second, you cannot feasibly brute force a “secret code” that has 115 quattuorvigintillion possible values (and yes, that is a real number!)
J.J. Shank (1 month ago)
"AI could crack any secret code." Would you please justify that?
SAL (1 month ago)
What makes you think AI can crack any code? maybe you are thinking about quantum computing? but even then, it is well known that there are several types of encryption methods that are immune to quantum computing hacking.
Want (1 month ago)
If you created a cryptocurrency, what would you call it? For me, Wannes.
Socialismo Científico (1 month ago)
Definitely a very clear and didactic explanation. Thanks.
Jas Wanth (1 month ago)
please do more videos on this topic , we need more videos on this blockchain technology?
Chris CR (1 month ago)
Buy Ripple!
Chris CR (1 month ago)
​+Alonzo C exactly!
Alonzo C (1 month ago)
Yes we all should buy one of the most centralised currencies and most easy to take down :)
Jaikrat Singh Tariyal (1 month ago)
Everywhere its the Alice who is the culprit :)
Weihong Li (1 month ago)
Furkan Demir (1 month ago)
Altyazı yarıda bitti aq senin
ahhhwh (1 month ago)
Stouffer (1 month ago)
Very nice, but I’ll stick with paper notes in my wallet.
SAL (1 month ago)
works fine until hyperinflation hits your government currency, then you might die of hunger.
Nicholas C. (1 month ago)
is it just me or does this system sound loopholey, a trust system based on computational power, money that can b created by stacking cpus, it just doesnt sound mature enough to replace the present financial fiat money system, i hope they improve the protocol, normally innovation curves go from old outdated system to new hype system, and swing back to a stable compromise, maybe full decentralization is not the answer, im not stating a fact, i just got a feeling about this man a feeling of immature tech that could be running headfirst into a reality check
J.J. Shank (1 month ago)
The world is too big for a single individual or organization to stack enough CPUs. Some estimates put worldwide computing at around 10^21 flops. Even the most powerful supercomputer, Summit, can only manage 10^17 flops. You would need to run ten thousand Summits to have a reasonable chance of forging blocks. It's just not feasible.
SAL (1 month ago)
Meh, we'll wait and see. As a counterpoint, we already have examples of decentralized/open internet protocols that haven't become outdated.
May Zhou (1 month ago)
20:44 But what if after a while, Alice has more transactions to Bob than the other miners, and then he would accept Alice even if she is trying to fool from Bob? What would happen after all to Bob's transactions?
arsenalacid (1 month ago)
This is literally the best thing on YouTube atm
Wow this really is an informative video. I guess BenePit.io is riding the waves of cryptocurrency also by tokenizing people's phone use.
Matthew (2 months ago)
How could you make a video about Bitcoin and not include an address for tips???
Mohsen Kazemi (2 months ago)
Amazing video. Thanks a lot!
Mohamed Hasan (2 months ago)
Thanks for your amazing videos !! How Cryptocurrency gets its value in the real world? for example, how and why Bitcoin got so high like this?
Jacek Soplica (2 months ago)
Ledger This is example of hash table ? For me it looks like linked list , not exactly but similar
Entrepreneur Silas (2 months ago)
I mine bitcoins. You need to start mining bit coins too. Click on this link for more information. https://bitclubnetwork.com/sgatambe/signup.html
zopim savo (2 months ago)
Arjeet Agarwal (2 months ago)
Informative video about cryptocurrency.. Great graphics...
Steve Nippress (2 months ago)
hy nguyen (2 months ago)
wow. best explain i have ever watch.
hy nguyen (2 months ago)
i wish i can spam you like button more
Mehul Gupta (2 months ago)
But I did not get how does the value of Bitcoin vs real money fluctuate? And moreover is everyone's entry in ledger broadcasted to everyone else's ledger in the world? Because considering the limit on amount of transactions per second this becomes unfeasible of sorts as a currency.
SAL (1 month ago)
​+Mehul Gupta It might seem like that at first glance, but actually, the supply rate of bitcoin is fixed regardless of how many miners join or leave the network - the *difficulty* of mining is adjusted periodically to ensure a new block roughly every 10 mins. In this regard, bitcoin is unlike gold, because with more gold mining, there is more supply - not so with bitcoin.
Mehul Gupta (1 month ago)
So that implies more the number of miners, more the value of Bitcoin depreciates?
SAL (2 months ago)
Same way as gold and stocks - value fluctuates based on global market demand. yes, broadcasting every ledger entry to every node is inefficient, but it ensures total global consensus of the ledger. the idea to scale will depend on building 2nd layer technologies, such as the lightning network to get hundreds of thousands of transactions per second.
Gary Du Charme II (2 months ago)
The only thing I still dont understand is how bitcoin becomes a real currency that is exchanged with dollars/euros/etc. Like the functionality makes sense and how you create it/ add more to it. But how does it have any value compared to real money?
SAL (2 months ago)
it has real value based on the desire of people worldwide wanting to accept it and hold it.
Ajay Joshi (2 months ago)
Jérôme Blanchet (2 months ago)
Put Andreas Antonopoulos Book's Mastering Bitcoin into this kind of video, and you will it billions view
Ahmed Sadman (2 months ago)
Undoubtedly the best video on cryptocurrency
Rian Doren (2 months ago)
Free miner BTC in mac os https://www.youtube.com/watch?v=rVyFvVReN5Y
Sanket Itnal (2 months ago)
Coming to 7:00 minutes. What if Alice disapproves to sign the transaction ?
SAL (2 months ago)
if no signing, then no transaction will take place from alice to bob.
Arnav Rawat (2 months ago)
Man your videos are a relief from the bullshit of the real world
Steven Roy (2 months ago)
Technocratic totalitarianism is the end goal.
PartimeVillian (2 months ago)
Sweet baby Jesus, it finally makes sense! Thank you my dude!
Antonio (2 months ago)
Niobio Cash (NBR) is a Brazilian digital currency, see in this video the president-elect bolsonaro talking about niobium, enjoy and acquire this promising currency @ @t
J.R. Vasquez (2 months ago)
As usual, excellence. Thank you 3B1B!
Bismuth LD (2 months ago)
Basically, figure out how to reverse enginere SHA256 and you own the world. You could set up a computer to reverse enginere the hash function, then win the bitcoin lottery every single time.
J.J. Shank (1 month ago)
You could do a lot more than win computational lotteries.
jeff mcdonald (2 months ago)
Great job. I'd love to see you go over Proof-of-Stake at some point.
Nikishiva Kumar (2 months ago)
J.J. Shank (1 month ago)
Did your space key break?
Vishal Lavania (2 months ago)
10 years, phew!
Kevin Phoenix (2 months ago)
Bitcoin is more like money 💵 than any other money 💶 ever conceived 🏦
Kadri Vatman (2 months ago)
Thanks for the great video! Concerning the Proof of Work, what defines the number of zeros at the beginning of the hash? Thanks!

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