Intro to Ethereum Dapps - YouTube

- [Narrator] In this lesson, we'll learn about building

decentralized applications or Dapps.

But first, let's take a minute

to appreciate the difference between Dapps

and regular web applications.

In traditional web application architecture,

there is a Front End client, and a Backend server.

The Front End is written using HTML, CSS, JavaScript,

and the backend is written in a framework

of your choice like Rails, Node, or Django.

The Front and Backend interact with each other

by sending JSON messages over HTTP.

There is typically a hosting service involved

where your Backend is running like AWS.

With decentralized applications,

there's also a Front End client and a Backend server.

The Front End is written using the same

HTML, CSS, JavaScript, but for the Backend

we would use a block chain like Ethereum.

The Front and Backend would still be interacting

with each other using JSON messages.

This architecture is a bit oversimplified,

but the point is that the end user will not

be able to tell whether they are interacting

with a Dapp or any other regular web app.

The change would be invisible and in the background.

The traditional client server architecture

is so common that it's rarely revisited.

Should we still be building apps this way

knowing everything we know now?

Let's take a look at some of the issues

with the traditional client server architecture.

The first issue is that your server

is running on a Centralized Hosting Service

who you outsourced your hosting needs to.

As more and more people around the world

use the same popular hosting service,

it becomes a bigger single point

of failure for the entire internet.

Think about it, to take down all the sites

that are running their Backend

on this popular hosting service,

all you have to do is disrupt this one provider's

infrastructure in order to take down

potentially half the Internet.

This isn't a very resilient architecture for the web.

It's also an increasing amount of pressure

on a singular organization, to expect them to build

and maintain all this infrastructure

for the entire world.

Centralized servers are also easy to censor and control.

Taking down a web application is as simple

as removing it from the centralized server.

This can happen at the state level

where government agencies request hosting providers

to take down certain websites

they may not like or agree with.

But if your application was running everywhere,

taking it down would not be as straight forward.

To censor a block chain application,

you would have to take down all

the networks nodes simultaneously.

The Ethereum block chain currently has

over 25,000 nodes spread around the world.

When we increasingly rely on centralized services,

we create honeypots of data for attackers.

We've seen this time and time again with various hacks.

The most recent being the Equifax hack.

Equifax is a centralized credit reporting service

and they were responsible for maintaining

millions of users personal credit information

including their social security numbers.

Millions of people put their trust in this one organization

to keep their data safe from getting into the wrong hands.

As a potential attacker, it's very lucrative

to hit just one database and get access

to millions of people's sensitive data,

that you could then use to open credit cards, for example.

With the decentralized database, like a block chain

data attacks are not as trivial

as getting access to a single database.

Another issue with the traditional client server

architecture is that of data integrity.

Along with your Backend server,

the database powering your application

is also likely running on the same hosting service.

Assuming you trust your hosting provider

a hundred percent this isn't an issue.

But how can you be sure?

What's stopping an unauthorized employee

at the hosting service from making changes

to the data in your database?

And what if your database contained people's

sensitive information like their bank account balances?

That's an awful lot of trust to put into

any single organization with the most valuable

part of your application, which is your data.

In fact, data is so valuable that many companies

are built on the very premise of selling your data.

They do this by creating a centralized website

for users to interact with by either posting photos

or entering search words.

They record your interactions to a database,

and then sell your interaction data to advertisers

for lots of money without your knowledge or consent.

Think about that.

All the data that is generated by everyone in the world

is monetized by only a handful of companies.

With decentralized applications,

users can regain control of their data

and decide for themselves whether to monetize it

by choosing to sell to advertisers or not,

and they get to keep the money, not some other company.

Protecting from data failure is another issue.

Unless you are making the extra effort

to create backups and replicas of your database,

there is no guarantee of surviving catastrophic failures.

Everyone running a database with their application

has to take on the responsibility

of backing it up as well.

There is no standardized process for creating these backups

and some organizations may not even create backups.

Some may even mishandle the backups

and place them in a vulnerable place

for attackers to take advantage of.

With the block chain, everything is publicly readable

and redundantly copied to various nodes of the network

ensuring that the data is never lost.

Even if a certain number of nodes go down,

the database can still continue to work.

All this isn't to say that block chain applications

are the silver bullet to all the webs problems,

since they do come with their own limitations

which we'll explore in the coming lessons.

But block chain applications do provide

a new level of baseline guarantees

that aren't found in other popular systems,

like superior fault tolerance and trustless execution.

In this context, trustless execution means

not having to trust any person or organization

to execute your code as your wrote it.

We can use cryptography or math

to provide a guarantee of the execution of your code.

Now that we understand some of the unique benefits

of writing block chain applications,

we'll build a simple block chain

Explorer Dapp in our next video.

Thanks for watching and see ya next time.