Bitcoin - Transaction block chains
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- čas přidán 30. 04. 2013
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The mechanics of a bitcoin transaction block chain, which is a construct that is generated by bitcoin miners and functions as a global ledger for recording and validating bitcoins.
More free lessons at: www.khanacademy.org/video?v=Qz...
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.
this video series is really awesome, now i can grasp it better!
Very Helpfull presentation! Thanks
This video helps me a lot, I thank you
Thank you for sharing this tutorial
So which one contains the information about the bitcoin transactions: the "challenge" or the "proof of work" (which by the way is the same as a solution to the equation, right?)? If the bitcoin transactions data is included in the "challenge", then each computer's "proof of work" is unique to itself, isn't it? (not that it's a problem), because it contains the coinbase transaction. If the "proof of work" contains all the transaction data however, how can you make sure that the computer has not edited reciever/amount/etc of OTHER transactions than only the coinbase transaction?
I guess
that is the entire point of the blockchain - all transactions are found in the previous blocks. anyone can verify all that transaction data to see that nothing has been edited.
So... in order for the nodes to verify transactions for any given Alice or Bob they need to look at their previous transaction records which are contained within the block chain. So do nodes need to decrypt the block chain back a certain number of iterations to find those records to verify them? What I don't understand is how information on previous transactions is not lost inside the block chain eventually? It seems that by iterating those hash functions back months or years you would lose data at some point. Or does the block chain get longer as time goes on to incorporate more data?
All transactions are forever stored as part of the blockchain (no data is lost), so you are correct, the blockchain keeps getting bigger with time. also, the transactions are not encrypted.
Maybe i misunderstood it but at around 4:15 mark the blockchain shown has arrows pointing the wrong direction right? Each block depends on the previous block not the next block that has not even been created yet.
@changetip thank you!
I have doubts request you to please clarify ..
1 . I read every block can contain 1 mb data ( let say around 10 transaction)so suppose in one time stamp there are 100 transaction so how miner are picking the transaction or this will be grouped 10 each..
2. If not in grouped then suppose miner are choosing transaction . So if 1 miner working on 1 to 5 and 15 to 20 transaction and another working on 1 to 10 so when they post their block who will get money for transaction 1 to 5..
There is going to be a queue of transactions (called the mempool) waiting to be included in blocks. If a miner includes certain transactions in a block then the rest of the miners cannot mine them in subsequently mined blocks.
Is it possible for the fork to get very large - for example global internet problems during a world war, a big net split and two long chains developing. Or can somebody apply a supercomputer or some kind of distributed computing to older transactions and outdo the current chain with one of greater complexity?
The explanation rarely becomes easier to digest after you prepend it with the oft abused 'basically' and 'essentially'.
You could theoretically encounter strange situations like this if not all nodes could communicate with each other. However, once there are two "different" chains out there, (honest) bitcoin mining nodes will start building on top of the one with the most work put into it.
@Khan Academy what happen to the data or bitcoin that is going to be receiv by the receiver no one mention this part...we know trasaction will be verify by the node, block will be created and verify the block and the miner will get the rewards but what about the actual bitcoin that has send to the receiver?????? when will he receive???? not even a single video mention about it...please kindly explain me I'm new to blockchain and have a lot of doubt and confussion.
Do you use Bitcoins and/or associated with them in anyway? Just curious.
Thanks
If you hash multiple transactions into one block, how can you figure out about each transaction? For example, when Alice pays Bob again, the nodes will have to check that Alice has enough money - by tracking down all the past transactions and recording the gain and loss by Alice. How could the nodes do that if the transactions are hashed?
even though transactions are hashed for the next block, they are also still kept "as is" in the blockchain. The nodes simply need to look for the specific addresses alice presented in the transaction. Nodes have no concept of "alice", they only know addresses.
What happens once the last coin is created?
At the end of this video the speaker says that the longst chain is the one that shows the most effort made. So, basically is saying that the total amount of valid blocks is not a parameter to measure length?
I guess if total number of blocks are the same, then the next criteria might be max effort
when the bitcoins reach their max, 21million (i think), are the rewards for the miners simply the transaction fee? Is it a problem that there is a transaction fee; how high can this fee become?
Yes. Maybe. Good question
How is the coin base award calibrated? It is like the inflation rate, right? Why it's 21 million capped?
If dishonest nodes had enough computation power, they could try to cheat the system by outdoing the current chain. However, as long as the honest nodes collectively have more than half the computing power, it will be an uphill battle for the dishonest nodes. It just takes one honest node to win the race and solve the proof of work first. Also, if you have the computing power, you're financially better off using it for good (e.g., bitcoin mining), so that's an added incentive to behave well.
Hey Matt...I sent a small transaction of bitcoin from my Copay wallet (v3.2.1), however forgot to insert a recipient address (left the bar blank). How do I recover these funds or move them to the recipient?
The transaction says the funds have been "moved". I sent these funds On the 25th May, 2017
Any help would be appreciated!
Any input bitcoins not redeemed in an output is considered a transaction fee; whoever generates the block can claim it by inserting it into the coinbase transaction of that block.
To prevent double spending. The reason is we need to know how much money all accounts have.
in bitcoin why is there a "chain" cant the transaction be completed then that information deleted? why is all the information saved as a chain all they way back to the start?
Because the ledger doesn't give you balances. It stores all the transactions made between addresses so to calculate a balance you need the whole Bitcoin history to add inputs and substract outputs of a given address.
Woow woow
What happens when there isn't any more reward incentive for miners? Will people start competing for the lowest fee? How much will it cost to use bitcoin?
It is expected that in the future more transactions would fit into a block, and fees will be higher than now. So it is assumed that there will always be miners trying to find blocks and collect all the fees.
Have you try to trade bitcoin on Forex and see how much you make in a week.
Fee will be determined by the market, no way to know exactly how large or small it will be. Won't be large enough to hinder exchanges, obviously. And will be competing with other methods of exchange. The fee will have to be smaller tan other methods, or if larger, provide an advantage to overcome this fee differential.
this is a question that puzzles me for many years, will each of the node keep a copy of the global transaction ledger? I guess that will need huge amount of storage, right? another question is, will this transaction be broadcasted to all nodes? there could be billings of nodes in the world, will this transaction be broadcasted to all of them? that sounds unrealistic. appreciate your answer.
Yes. Every transaction is boradcasted to every single node in the world, regardless of how many there are. The more nodes there are, the more secure and decentrilized the network is, in other words, the more the better. It is known that Bitcoin has a scalability problem which other projects (such as Cardano) are hoping to solve in the future with a technology such as Sharding, meaning that each node will only have to process a portion (a shard) of all the transactions.
So bitcoins are representative of the transactions that a person made previously. However, when the first person wanted to make a transaction at the very beginning of this system, the person had no transaction history which means the person had no bitcoins. How did that person initiated the transaction without any bitcoins?
Each block mined by a user rewards the user with new coins. First there were blocks mined that didn't have transactions, and now blocks are mined that do have transactions.
time = zero?
I've gone cross-eyed
It will become large
thanks for sharing the information is high value but has no subtitles in Spanish what is limiting the bitcoin community of Spanish and Latin-speaking America.
juan pablo It's neither subtited in german or french or polish or russian or ... so what?
If you know both languages why don't you supply translation ?
The world makes sense now.
the first miner to come up with that [00000000000000000000000000...] number is the one who gets the reward, right?
어렵다.. 이건 칸아케데미 수준을 넘는다
I don't understand
The transaction fee will be decided by the user making the transaction. The higher tip (or transaction fee), the higher the probability it will be mined. But this is like 100 years off. This is kind of irrelevant to you and I unless you intend to live for a few more centuries.
sounding like a young Sal over here
I still do not understand it. It is complicating. Can somebody tell me how is bitcoin formed and how or where will I start to make money out of it. Thank you
Bitcoin is now worth $6400~ did you get any at that time?
You better did :)
Because that's what satoshi set the math to work out to.
Too much jargon.
Miners will basically qualify or disqualify transactions=CENTRALIZED...your jargon is overtly convoluted...similar to the explanation of fractional reserve lending...MINER= MIDDLEMAN. Period.
Sorry..but very confusing
Nerd talk is confusin'
👆👆 I've been earning massively from this dude lately... He's a Bitcoin mining Expert 💯!!!.......
This is a poorly done video because there are lots of concepts and jargon thrown in. Using words like hashing and not explaining it is not good. Using terms like time zero make the explanation confusing. Obviously not Sal. And just repeating the sentence doesn't make it easier to understand. Stop using jargon to doing smart, speak with simple, direct words and if you introduce any concept - please explain it before you continue on. If the viewer doesn't understand that concept you just glazed over, the rest of the video is useless and frustrating. Sal repeats things using different words - he is empathizing with the listener who might not know simple things like what a universal ledger is.
no offence but if you dont know about words like hashing you should start learning about bitcoin in more beginnervideos, that explain words like that. What you say is like arguing on a mathematical tutorial about the pythagorean theorem, that words like hypotenuse are used instead of saying "the longest side on a right angle triangle"
Delete this
👆👆 I've been earning massively from this dude lately... He's a Bitcoin mining Expert 💯!!!.......