Name: 擴展區塊鏈 - Computerphile (Scaling Blockchains - Computerphile)
Uploaded: 2021-01-14T10:13:26.000Z
Duration: 19 min 57 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

I'm going to talk about the issue of Scalability in Bitcoin but before that I will Provide Some

情態副詞

Background on Bitcoins and Then We'll Slowly Build it Up to the point where We can See the Issues in Bitcoin Scalability and what Is?

Being Done in Current Blockchain Designs to Address These issues in Scalability the key Metrics that, we are Looking at

Here Are the Throughput of the System that Is what Is the Maximum rate at Which Transactions can be Handled

By the System in Terms of writing Them to the Blockchain and

That Is from the point When A client Submits a transaction to the system?

How Long Does it Take until it's written to the Blockchain I

Think some History, Would be nice so bitcoin Appeared on the Scene in

2008 On an online Meaning Mailing List by a pseudonymous Author Called

Satoshi Nakamoto Whose Origin Is Unknown and

2009 There was A software Release of Bitcoin and it Generated A lot of Interest

Since its Inception because it went on to become one of the biggest Digital

Currencies of our Times so just Today a one Bitcoin is Worth About

$6,000 yet on the other end of the Spectrum There are People who have Said that

Blockchain is the biggest Bubble of our Times the Aspect of Bitcoin that Really Gives it its wings Is

The Blockchain Which Is at the heart of Bitcoin

Now A lot of People Have Started to become Interested in Block Chains Because These can be Applied to

other Scenarios Which Are Beyond its immediate Application to Digital Currencies

We did A video with tom Scott About online

Voting and The Blockchain was not mentioned at all but Lots of the Comments of People who Watch that Video Say?

Why can't We do voting with a blockchain Is this one of the Applications you're Talking About

yes Exactly if You look at the Blockchain

One of the key Properties of the Blockchain that

Distinguishes It from Regular Traditional Databases Is that of public Verifiability and

Public Verifiability is enabled by two other Properties Called Integrity and Transparency

Now by, transparency, We mean That anyone can verify

How the State of Data has Been Updated and

Be sure that the Data that they are Retrieving Is

Not Corrupt and it is correct.  I can imagine that it would be a feats an

Engineer A system for 60 Million People Living in the Uk but Never mind how, Many People are Living in China or India

Or some of the other Nations That have got, Many, Many more People. Is that the sort of Scalability, we're Going to be Talking About

Well This is the Kind of Scalability that, We are Going to Talk about but Let's not Forget that Systems like Google or Facebook

Also deal With may, be much greater Magnitude of Users but the advantage that These systems have, over

Systems Like Blockchain Is that They are Centralized Systems that are under The Control of a single entity Or a consortium of

Entities While in A blockchain the Network Is

Between A Fully Decentralized Set of Nodes so what does a blockchain really Look like

Well you Can Think of a blockchain as a linked List of Hash Pointers so a hash Pointer Is Simply A

We are going to look at a linked List of Hash Pointers so in the Beginning We need to start from Somewhere so we have?

Dummy Or a Padding, Data Called Genesis Block and We Take the hash of This first Block?

Included in The Header of the next Piece of Data

So there is A hash Pointer Which points to the Previous Piece of Data and new Data then the next Block and it's Called ST-1

Then Imagine that you Have Another Piece of Data and this is the simplest Form of Lock Chain so as you can See

This is a linked List of Hash Pointers Now the hash Point Ourselves Two Purposes

The First Purpose Is that it Uniquely identifies The Previous Block of Data

IDentifies The Data and the Hash Pointers due To the Properties of Hashing Functions

Also Confirms that the Data has not, Been Corrupted you Can Think of it as a temporal evident Log and Anybody

Can independently Take Hash of this Data Match it with the hash included in The next Piece of Data

Compare These Two and if These Two Match then They can, be sure that the Data has not

Been Corrupted There Are Two Kinds of Operations That Can be Performed on a blockchain

One is a read Operation and one is A write Operation

Now as you might have guessed Read Operations are Easy Because they, Simply, Involves Retrieving, some Data of the Blockchain

However Write Operations Are More Challenging Because They Can

Potentially Hurt The Properties of Transparency and intake Integrity That We Expect From the Blockchain

So a blockchain has Two basic functional Components one Is to Validate Transactions and the other is to write to the Blockchain

We are First going to Talk about Validation of Transactions what is the Transaction?

You Can Think of a transaction IS an Operation that

Changes The State of Data That Lives on the Blockchain

Okay, so let's Look at A very Simple Example in The Context of Bitcoin

So a transaction might Look something like

Say Ten Bitcoins to Bob and This Transaction has Been Generated by

Alice now alice has Two things to Prove to the Blockchain Network

Alice first has to prove that She Owns These ten Bitcoins so she is able to Pay them to Bob which means that as input

She, also has to Provide the Id of the Block in Which alice Became the

Owner of These ten Bitcoins Say it was Zero Zero seven

And the other Thing that alice has to prove Is that it's actually

Alice who is generating this Transaction and not Somebody Else who is pretending to be to be Alice

for This Purpose She Takes Advantage of A cryptographic

primitive Called Digital Signature so She Basically signs this whole thing With her private key

To the Network Any Node That receives This Transaction if it wants to Validate This Transaction it has to perform two

Checks First to Check That alice Actually

Received Ten Bitcoins at some Point in The History of the Blockchain

So if You Remember the Structure of the Blockchain, was something like This and There Is this Head of This Blockchain?

Where Ellis Came Into the Ownership of These ten Bitcoins say it was this One?

so the first Check has Been Passed the other Check that it has to do Is

Confirm That Alice Actually possesses These ten Bitcoins and

That Up until now alice has not Tried to Pay These ten Bitcoins to Anybody Else Because then that Would be Considered a double Spend

Because Imagine if Alice has Already Paid out These ten Bitcoins to Charlie

Then She's not the current, owner of These ten Bitcoins even Though she, was at. Some Point in the Past

So that's Another Thing that the Node has to confirm that from the point when These ten Bitcoins Came

She did not at Any Point Transfer Them to Anybody Else if The Transaction passes Both These checks then the next

Step is to write it to the Blockchain now this Would be Straightforward in A centralized System

Where There are all trusted Nodes and They'll Just Simply perform the right Operation?

However This is Significantly more Complex in A fully, Decentralized Network like that in The Blockchain

Because all the untrusted or semi Trusted Nodes Have to reach an Agreement Among Themselves

Whether They Are going to write this Piece of Data or transaction to the Blockchain or not

This is where The Issue of Consensus Comes Into Picture

Consensus Simply Means to reach Agreement About A value Among Multiple Nodes Within a network

Now in The case of Bitcoin this Consensus is done

字幕列表影片播放

擴展區塊鏈 - Computerphile (Scaling Blockchains - Computerphile)

sort

context

majority

multiple