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  • So what exactly is a blockchain?

  • Blockchain is a distributed database that stores information in blocks, what you can

  • think of as a kind of virtual container for data.

  • As new data gets added, additional blocks are created.

  • The blocks are then linked together chronologically to form a sequence of blocks called a chain.

  • As new information gets added, the chains get longer.

  • This method of data storage is called nondestructive, meaning old data never gets erased or overwritten

  • because the previous blocks in the chain remain unchanged.

  • Each new block that is written contains something called a cryptographic hash, a small mathematical

  • fingerprint of the blocks that came before it in the chain, making it extremely difficult

  • to tamper with the data that resides inside the blocks.

  • One of the things that makes blockchain so powerful is its distributed nature.

  • Distributed in this case means that data isn't just stored in one centralized database controlled

  • by a single account or administrator, but across a wide-ranging network of computers

  • called nodes.

  • In fact, the capacity for global networking itself is the very core of how blockchain

  • works.

  • Modern distributed computer networks began in the late 1960s with ARPANET, a precursor

  • of the modern internet, which connected computers at research universities out West.

  • But peer-to-peer networks, which power block train's communication and are so central to

  • its functionality, are a much more recent invention.

  • The first well-known peer-to-peer network was Napster, which appeared in the late 1990s.

  • Napster-- as you probably remember-- allowed users to share music files between their personal

  • computers.

  • Each node-- or independent computer on the network-- has the ability to share data with

  • all of the others without being coordinated by a central computer.

  • To continue with the music metaphor, peer-to-peer networks that power blockchain are like an

  • orchestra without a conductor.

  • Each node is a musician listening to a vast symphony and playing its own music by ear.

  • Okay, so now we know that block chains organize data in blocks, and we know that blockchains

  • can use peer-to-peer networks to distribute and store data all over the world.

  • But how does the blockchain know which nodes have accurate information?

  • In other words, how does blockchain know what data is authentic?

  • If any node can modify the chain, what's to stop a malicious node from trying to fool

  • the rest of the network for its own advantage.

  • That's a problem called consensus; which is really about maintaining agreement on a network.

  • Consensus, as it turns out, is a very old kind of challenge, which mathematicians and

  • computer scientists call the Byzantine General's Problem.

  • What's an ancient general got to do with blockchain?

  • Well, sending out messages between multiple parties and making sure they are valid is

  • a problem that people have been struggling with for thousands of years.

  • Imagine you want to send out a message to your army that says "Attack at Dawn", but

  • your message is intercepted and replaced by your enemy with a counterfeit message that

  • reads "Retreat at Dawn".

  • If that happens you've got a serious problem on your hands.

  • On the battle field and in finance, there are a lot of ways things can go wrong.

  • But here's the headline: blockchain claims to have solved the Byzantine Generals Problem

  • using unique properties of high speed computer networks and massive number crunching power.

  • There are a number of different 'Consensus Mechanisms' that blockchains can use to do

  • this.

  • But to give you can idea of how consensus works here are some of the broad strokes.

  • Participants on the blockchain use their computers to simultaneously solve very hard math problems.

  • When one node successfully solves a math problem, a new problem is generated and all the computers

  • on the network switch from solving the old problem to solving the new problem.

  • Solving hard math problems takes time.

  • But because blockchain keeps full records of al the changes that have occurred, and

  • nothing is ever thrown away, the sequence of answers combined with the times the answers

  • were sent out to all the other nodes on the network, allows the entire network to validate

  • that the data hasn't been tampered with.

  • We've simplified this view of blockchain; there's a lot of wonky math going on behind

  • the scenes but if you followed it along so far, you've probably got a pretty good idea

  • of the general way blockchain creates trust in a distributed network with no single party

  • in charge.

So what exactly is a blockchain?

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ブロックチェーンとは?解説者 ビッグストーリー リアルビジョン (What is Blockchain? Explainer The Big Story Real Vision)

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    robert に公開 2021 年 01 月 14 日
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