Blockchain Full Course | Full Blockchian Tutorial | Code Eater - Blockchain | English

hi welcome to co-readers blockchain

channel my name is srivastav and I will

be your instructor for this blockchain

course in this blockchain course we are

going to talk about a lot of different

things I have divided this full course

this full blockchain course into three

modules that is module a which will be

all about blockchain how blockchain work

why do we need to study blockchain each

and everything we are going to cover in

module a then we will have module B

which will be all about cryptocurrencies

what are cryptocurrencies what is the

difference between a token and a coin

and a protocol all those things if these

things are sounds unfamiliar to you so

don't worry we are going to follow each

and everything in depth and then we are

going to talk about smart contracts what

is a smart contract where we where do we

deploy our smart contract each and

everything about smart contract we are

going to talk about in modern you see is

there any prerequisite to take this

course there is no prerequisite to take

this course anyone having no knowledge

of blockchain having no knowledge of any

technical Co-op topic can take this

course okay and now let us talk about

what are the contents that we are going

to see in each module because we are

definitely I have divided this course

into three modules but what are the

contents that we are going to see in

different modules let's see that so in

module a we are going to talk about what

is blockchain

then what is a hashing algorithm because

this is one of the important concept

that you must know when you are starting

with blockchain then what is immutable

Ledger then distributed P2P Network

because our whole blockchain network is

actually working on distributed P2P

Network so we will see that then we will

talk about what is mining and then

consensus protocol okay then in module B

we will start with Bitcoin what is

bitcoin Bitcoin monetary policy Mining

nons and let me tell you we are going in

depth of money because I know mining is

one of the most uh I will say most

demanding topic or people wants to know

about what is mining so we will look in

mining a great detail and nonce is

related to mining so we will talk about

that we will see the different

technologies that we use in order to do

mining like CPUs gpus A6 and all those

things then we will talk about mempool

very important thing if you do not

understand what is memory and all those

things don't worry you will understand

at the end of this course

then we will talk about the different

transaction different type of

transactions and all those things then

wallets and how wallets Works what are

utxos each and everything

and at the end of this module we are

going to see what is a public key what

is a private key what are digitals in

Natures what are the what is the

importance of cryptography in blockchain

we are going to see that

then in module C we are going to talk

about what is ethereum then smart

contracts because smart contracts are

programs that are written on ethereum so

we will see that then we are going to

talk about decentralized applications

evm and gas now this is something might

might be a new term for you but don't

worry you will understand at the end of

this module then what are Dows these

centralized autonomous organizations we

will see that

what is hard for what is a soft Fork we

will see that

what is Dao attack there was an attack

on Dao on ethereum we will study about

that so that we do not end up in the

same place

and then we are going to talk about icos

that is just like IPOs we have IPOs in

you know in our traditional World in

blockchain world we have initial coin

offering so we will talk about icos

and at the end we will talk about

alternate coins or all coins means coins

other than Bitcoin so you can clearly

see that all these modules if you will

see it is a pretty big course we are

going to see each and everything in this

course

so it will be a lot of fun you will

learn a lot that I can guarantee so I

hope I will meet you soon in the next

video I hope you are excited for the

next video

and I think this is one of the most

fundamental question that everyone must

ask whenever he or she is starting with

a new course right so let's start with

why study blockchain what is the reason

for studying blockchain let's see that

and we will understand this with the

help of story of Internet okay let's see

how internet came into existence and

where internet is actually lacking and

what Gap can be fulfilled by blockchain

so if we talk about our communication uh

if we talk about early times so this is

how we used to communicate using pigeons

if you have watched I will say Harry

Potter in that case you might have seen

that owls were being used in order to

communicate in order to send messages

right in order to send a message from

one place to another so these were the

times when we have this mode of

communication where pigeons were used as

a transporter transported transporter

for our letters right then we have post

office right mailboxes that we started

with writing letters and to our friends

who are relatives

but it was also a time taking process

right it took around months or sometimes

even more than a month uh when we have

to do uh when we have to use these post

offices right

and today if we talk about in the era of

Internet

everything is so easy right

communication has become so smooth now

we can talk to so many people at once we

can talk to to our relatives or to our

friends who may be in a different part

of the world and still we may be able to

communicate with them just with the help

of emails right and then we have another

great invention that is Facebook or I

will say social media through which we

can communicate with thousands of people

in just a click right

now currently I am able to communicate

with you definitely it is a one-way

communication but still I'm able to

communicate with so many people at once

and this is all because of Internet so

one this one thing is for sure here that

internet has bring a revolution when it

comes to communication right internet

has made our communication part so easy

that we cannot even like live without

internet right today if we have to live

without internet it will be a disastrous

day right for us

but there is something where internet is

lacking definitely communication part

has so easy now but there is one point

where communication where actually our

internet is lacking and that point is

Trust

we cannot trust the internet and let me

explain you this with the help of an

exam now let us understand this with the

help of an exam let's say this is an NGO

where you want to donate some money okay

and for denoting our money for donating

money what you did you did a internet

transaction okay so now

you have donated some money to this NGO

via internet transaction

but the problem is you do not know

whether this NGO is going to use this

money that you have transferred to this

NGO via internet whether this NGO is

going to use this money for a good cause

or not whether this NGO is going to use

this money for women education child

education or some good welfare work or

this NGO is going to do some money

laundering or let's say you know funding

some terrorist attacks so you do not

know right and this is one of the reason

that many of the times we do not donate

to different organizations because we

have a fear in mind that what uh what

happened if they are using our money for

some you know bad practices so that's

why we do not donate so the thing is in

this whole picture you can clearly see

that we cannot trust this NGO and why we

cannot trust this NGO because we cannot

trust our internet because we do not

know the internet transaction that we

are doing where this money is actually

going so one thing is for sure internet

cannot provide trust to us so the only

technology that can provide trust to us

is blockchain with the help of

blockchain we can bring Trust on the

table and how this how this like

blockchain works you will understand

because I'm not going into depth of

blockchain currently but one thing is

for sure you can trust this blockchain

technology and trust is the thing that

internet cannot provide you once we will

move on to blockchain application you

will understand how blockchain is

actually bringing trust to the table

okay so if we talk about blockchain

blockchain is a disruptive technology

just like internet internet made our

communication part very easy one of the

most important human element right human

thing that we need to talk to people we

need to communicate to people

if we talk about blockchain blockchain

is bringing trust to the uh to this

communication now we are not just

communicating we are doing communication

when like while trusting someone and how

this is so we will talk about it but

this is the reason why blockchain is

getting so much popular and this is the

reason if you will see in these two

pictures blockchain is just acting like

internet acting in the sense like

internet brought a revolution to the

communication part blockchain is

bringing Revolution to this trust part

and that's why blockchain is getting

famous day by day and it will be famous

just like internet or more famous just

like internet so there will be huge

opportunities when it comes to

blockchain in the near future currently

there are also lot of opportunities but

in the near future you will see

exponential exponential growth

opportunities in the blockchain domain

and that's why we need to study

blockchain now in this video we are

going to talk about what is blockchain

this presentation will be a very I will

say interesting presentation you will

enjoy a lot let's start this

presentation so before talking about

blockchain it is very necessary that we

should know who are actually inventors

of blockchain now if I will ask you what

do you think who is inventor of

longshare and who are inventors or

blockchain please let me know in the

comment below I want to see what is your

answer

I hope you have commented your answer

but I know most of you like what have

actually commented there most of you

might have thought that inventors of

blockchain or inventor or blockchain is

Satoshi Nakamoto but let me correct you

here Satoshi Nakamoto is inventor of

Bitcoin but not blockchain inventors of

blockchain are Stuart Herbert

and W squats tornado so these are the

two people who are actually inventors of

blockchain they have written a paper on

it I think it was the paper was of

around related to digital signatures or

something I will share the link in the

description so that you can also read it

uh it was around 1990 they have

published this paper

so remember inventors of blockchain are

Stuart Harbor and W score store Neta and

not sadoshi Nakamoto okay many of the

times you will see this false

information on the internet but I want

to correct you here only so that you do

not get you know uh get this that

correct incorrect information now let's

talk about what is blockchain so as you

can see on your screen that we have this

blocks right connected with each other

and hence we have something like a

blockchain right means chain of blocks

but definitely you cannot Define

blockchain like this right so let us see

our definition of blockchain let me tell

you there is no fixed definition of

blockchain but this is one of the

definition which I think uh you know

identify the blockchain the most good

way so that's why we will take this

definition

so blockchain is a distributed immutable

Ledger which is completely transparent

okay let me repeat it for you blockchain

is a distributed imitable Ledger which

is completely transparent now let us

understand the meaning of this

definition let us understand the meaning

of each keywords that I am using in this

in this definition that is ledger

immutable distributed transparent

everything okay so I will start from

Ledger then we will go to immutable then

distribute it and then we will talk

about transparent okay so let's talk

about what is a ledger so a ledger looks

something like this so Ledger is

actually a place where you write all

your debit as well as credit entry so

let's say you might have seen that

whenever you go to a shop let's say or

if you have let's say you went to

McDonald's or something so what they are

doing is they are actually writing each

and every transaction like if you talk

about a normal shop keyboard okay so in

that case what they're doing is they are

writing each and every transaction in

their notebook that what amount they owe

you or what amount you owe to them each

and every transaction is actually being

written in this Ledger book okay so this

is the traditional approach which people

use before computer sometimes you might

see this but now in most of the error

like in at this point of time what you

will see that people are using computer

in order to write down all the

transactions so you might have seen that

whenever you go to McDonald's and you

buy something they are writing each and

everything in their calculator type of

thing right and that's why that's how

they are providing you receipt and

everything so what they are doing is

actually they are recording the

transactions like how much you are

paying how much the change they have

given you each and every transaction is

being recorded in that ledger okay so

Ledger is a place where transactions are

recorded

now this is how real world operates okay

this is the real world Ledger if we talk

about blockchain in blockchain the

blocks of the blockchain act as Ledger

so we have seen right that our

blockchain is formed by various block

connected with each other via chain

and this block in the blockchain

works as a ledger for the blockchain

where each and every transaction are

being recorded so let's say you are

paying some Bitcoin to your friend let's

say ace and five Bitcoin to B now this

transaction will be recorded on this

block of the blockchain and then like

this only if C is sending some

transaction to D some Bitcoin to D in

that case that transaction will be

recorded on this block of the blockchain

so this is the meaning of our first

keyword second keyword is immutable now

the problem with this Ledger is that

this Ledger is mutable or if we talk

about databases right the centralized

databases all those type of ledgers are

actually mutable mutable means you can

erase the data you can manipulate with

the data like for example I can just

remove this one of the pages from this

notebook right I can completely erase

one of the written handwritings over

this notebook if you talk about a

database so the person who is in charge

of that database can completely erase

one of the transactions from the

database so the thing with these Ledger

is that they are mutable you can mute

them means you can change them but when

it comes to this block of the blockchain

these are totally immutable means once a

transaction is recorded on this block of

the blockchain you cannot change that

transaction nobody can change the

transaction that transaction is like

permanent on this blockchain

and how this is done we will talk about

it so don't worry about it but now I

just want to tell you like how what is

the meaning of these keywords and why

blockchain is so special okay so now we

have understood the meaning of two

keywords Ledger as well as immutable now

let's look at the third keyword

so if we talk about a blockchain network

this is how a blockchain network looks

like okay so we have different computers

here these computers are connected via

P2P Network which we will talk in our

upcoming videos for now just imagine

that these computers are connected with

each other okay and each of these

computers as you can see the that they

are actually holding blockchain so a is

holding a blockchain and exactly like

whatever a is holding like the exact

copy is hold by B Means A and B are

carrying the same blockchain c e and f

are also carrying the same blockchain

means all of these people are having the

exact copy of the blockchain okay so all

of these people are having the exact

copy of the blockchain

let's say a new block is created now how

this is created we will talk in our

upcoming videos just for now let's say

that a creates a new block okay now he

will add this block to his blockchain

now what will happen a will start

communicating this information to b c e

and f okay saying that okay now I have

created a block please see this blog

please verify and validate this block

whether this block is right or not so

what bcef will do they will start

verifying and validating this block

whether this block is a malicious block

or not or whether this block is a

suspicious block or not if this block is

a correct block what they will do is

they will simply add this block to their

blockchain if you will see right all of

these people have added this block

created by a to their blockchain and

this is how blockchain is distributed in

nature you can clearly see the block is

getting distributed all across the

network

and that's why we called blockchain uh

distributed immutable Ledger

so this is like a is holding a ledger a

notebook and a is Distributing this

notebook to all the people who are

connected with him okay

now what is transparent here so The

Ledger as you can see that ledger is

totally available with everyone right

whosoever is the part of this blockchain

network so The Ledger the transaction

that these Ledger will contain is

totally transparent to the public anyone

can see that transaction but there is a

catch here these transactions are in

encoded format so definitely people can

see the transaction that okay some one

has done some payment to someone but

nobody will know who that someone is

each and every data is included on the

blockchain so that nobody can read it

okay but the data is transparent in

nature everything is totally public

everyone can see everything but nobody

will able to decode everything okay and

that's why we call blockchain as a

distributed immutable Ledger which is

completely transparent hi now in this

video we are going to talk about the

different applications of blockchain

let's start so there are a lot of

applications of blockchain first

application of blockchain is product

tracking another application of

blockchain is smart contracts third

application of blockchain is Healthcare

System system fourth application of

blockchain is international wire

transfer and we are going to have a

closed lookup at all these applications

like how blockchain is actually being

used in all these different domains so

let's start with product tracking so

let's say you want to buy a coffee okay

so you went to the shop and you buy

bought this coffee

now according to this copy like

according to the packaging of this

coffee it claims that this coffee is uh

let's say hinted person pure coffee and

let's say this coffee is let's say for

example brought from Brazil okay just an

example

and you trusted this coffee package but

after some time you realize that okay no

this is not that coffee uh it is not the

Brazilian coffee like this coffee that I

have in my hand is a fake coffee means

this is completely you know false

advertising I will say

now how we can prevent from these type

of situation where we are buying

something

and how to know whether the product that

we are buying is actually a legitimate

legitimate product or not so for that

what we can do is we can use blockchain

now with the help of blockchain what we

can do is we can simply

track this product so this product let's

say this product has been tracked using

blockchain so this product will have a

barcode so you might have seen right

barcode in various shops now once you

will scan this product this product will

tell you each and every

thing this barcode actually tells you

each and everything about this copy copy

where it started like like you can

clearly see if you can see some of the

details are mentioned here like what is

the name of this coffee from which

country it is originated like what are

the different mode of transportation

like was done in order to bring this

coffee let's say from Brazil to India or

Brazil to USA so each and everything

will be mentioned in this

you know in this application now you

must be thinking like how it is

different from Amazon like Amazon also

does the same thing when we buy

something we have all the details but if

you will see Amazon so Amazon does not

provide you the details of a particular

product Amazon only provides you the

tracking ID like where your product is

where your product will be and all those

things right so your product is already

ready in the shelf and from that shelf

each and every movement of that product

is being tracked but what we are talking

here is we are talking about Complete

product tracking and how it is different

when it comes with blockchain because as

we talked about blockchain right

blockchain is a distributed immutable

ledger so once a transaction is recorded

on the blockchain no one can erase that

transaction so in the case of product

tracking once we have noted that okay

this project

was at this location on the blockchain

no one can erase that data from the

blockchain now this is the beauty of

blockchain and that's how it is used in

product tracking and you can also see

here that each and every information

about the product is being mentioned in

this application

now let's talk about another application

of blockchain and that is smart

contracts now this is one of the most

beautiful I will say applications of

blockchain so please be aware just be

alert here I will say so how smart

contracts are being used in blockchain

so first of all let me tell you one

thing that smart contracts are simply

programs that you write on blockchain so

like you have written program in C C

plus plus Java python or if you have

written in that case so just like these

programs right we have Smart contracts a

program written on blockchain simple as

that okay and if you still do not

understand what a smartphone net just

don't worry we you will understand it

after this example so let's say uh let's

take an example let's say there is a

person a he has a he has this food

delivery truck

and he delivers fruits okay so he's a

fruit supplier we can think of it AF

food supplier

and he does this food delivery to this

shopkeeper B okay so this is our

shopkeeper B who has a shop XYZ and once

he received these fruits from a b sell

these fruits to his customers now once

the delivery is done B pays some money

to a right this is how a business

transaction is done

but after some time B realizes that the

Apple sent by a are actually rotten so

now B is in loss he cannot use those

apple to sell his customer right because

if he will sell these apples to his

customers then their customers will be

highly disappointed in B because now the

fruits are rotten right

now what B can do in this type of

situation

now in this type of business transaction

for example what we can do is we can

install a smart contract okay we can

install a smart contract

and we are assuming that the temperature

to keep the fruits fresh is less than 30

degree celsius so this delivery truck

you can think of this delivery truck as

a refrigerated truck okay this track

this uh this container that you are

seeing right where delivery is written

it is actually a fridge okay we are just

assuming that this is a refrigerated

truck and the temperature in order to

keep these apples fruits apples fruits

apple fresh actually is less than 30

degrees Celsius okay so this is our

assumption

now let's write some logic to our smart

contract with our smart contracts are

nothing but programs right so we will

draw a flow chart here that if iot

directed a temperature greater than 30

degree celsius now what is this iot iot

is for now you can think of as

temperature detecting device so they

detect the temperature so we are

assuming that this iot is installed to

that container of the truck and if iot

is detecting a temperature of

degree less greater than 30 degree

celsius and this is not good for our

Foods right now if this happens in that

case we will definitely cancel the

delivery and we will not pay to a right

B will not pay to a in this scenario and

this is good if this is false if this

condition is false in that case

delivery will be done and B will be have

to pay to a means we cannot then deny

that I can I will not pay it away

because now I have received the fruits

and I do not want to pay today this is

not how this will be done when it will

come to Smart contracts

so this is how the logic of our smart

contracts will work and I think this is

a very good logic also now some of you

Ma some of you might be thinking that

how it is different from any other

program because you know we write

programs in C C plus plus Java how it is

different from any other program what is

so special about smart contracts

the special thing about smart contracts

is that smart contracts are actually

immutable in nature just like blockchain

you cannot erase the data from

blockchain right so this is smart

contract will be deployed to the

blockchain and you cannot change

anything from the smart contract once it

is deployed to the blockchain now this

is one of the beauty of smart contracts

means once this logic is written no one

can erase this logic first thing second

thing with the smart contract is that

you do not require any human

intervention means when I am saying that

if the temperature is greater is greater

than 30 degree celsius the if this

condition is let's say false then we are

transferring money to a right so in this

case money will be actually

cryptocurrency so these cryptocurrencies

will be transferred from Smart contract

balance to A's account now this is

something very I think a little bit

complicated to explain currently because

currently we are just progressing

towards our blockchain course for now

just assume that smart contract as

acting as a bank where some

cryptocurrency is deposited if this

condition will be false in that case

cryptocurrencies from a smart contract

account will be deducted and will be

transferred to a and who has transferred

this cryptocurrencies to Smart contract

account and that that is actually being

done by D okay and we will see this in

more detail in our smart contract module

but for now I think this makes sense to

you also right

so this is also one of the applications

of blockchain now let's see the third

application of blockchain that is in

international wire transfer so let's say

you want to send some money to one of

your friend okay so you went to your

bank sender bank and you want to

transfer some money to your friend

but in order to transfer this money to

your friend which let's say lives in USA

let's say you are living in India and

you want to transfer this money to USA

this transfer of money cannot be

directly done to USA means if this is a

Bank of India you cannot transfer this

money directly to USA so let's say if

this is our bank in USA this is our

receiver bank because your friend is in

USA you cannot transfer this money

directly to this Bank there will be so

many banks in the middle of this change

between the sender bank and between the

receiver Bank

now the problem with this approach is

you have to pay a huge amount of

commission to these banks in order to do

a international transaction so let's say

and this International transaction uh

fees can be around 10 to 25 percent just

it can be 10 to 25 percent so let's say

if you are sending one thousand dollars

to your friend for example one thousand

dollar to your friend in that case if

the uh percentage is let's say 10

percent then hundred dollars will be

deducted and your friend will only

receive nine hundred dollars and the

reason is because there are so many

banks involved here so they charge some

commission now this is a very heavy

commission right now if you are going to

use blockchain in this case yeah and one

more thing yes one more thing that this

process can be a slow process it can

take two or three days definitely it can

be less than that but it can take up to

seven days also seven to ten days also

because let's say there are banks that

are involved Within These two blanks

they are slow they are working very

slowly in that case definitely your

transaction will take a huge amount of

time and then your friend let's say

might receive the money after 10 days of

the transactions

you know this is a very slow process

right so what you can do is instead of

this instead of going like this what you

can do is you can do transaction on

blockchain now transactions on

blockchain are very fast it took around

let's say you are doing some

International transaction it will take

around some minutes and your

transactions will be done and top of

that that transaction fees will be very

less so that's also one of the beauty of

blockchain so we have cryptocurrencies

which we will discuss in much more

detail in our cryptocurrency module so

cryptocurrencies these cryptocurrencies

you can transfer from one place to

another in so much time like in less

time and in so much less amount of

transaction fees now let us look at

fourth application of blockchain that is

in healthcare system

so normally uh let's say if there are

two hospitals in City a and CTB okay and

let's say uh you are born in City a so

all of your medical history is actually

stored in the database of City a right

so since you are born in City a so all

your medical history documents each and

everything is actually stored in the

database of your CTA Hospital right it

can happen

now the problem in this approach is that

let's say you went to City B for some

work okay and you met with an accident

now in that case what will happen in

that case City B does not have your

medical history now in order to fetch

your medical history they need to call

your parents or let's say they have to

talk to different hospitals because they

do not know you might definitely they

will not call to hospitals until they

will call to your family right so your

family will then go to the hospital of

City a and then they will fetch your

records medical history and then they

will provide to City B right because you

can have different type of diseases

let's say you might have some sugar or

some diabetes or let's say you have some

like you know life-threatening type of

disease now in that case City B needs to

check your medical history before before

doing any type of procedure or it might

be too late for you to survive from that

accident right

so this is a problematic thing right

so with the help of blockchain what we

can do is we can share this data

definitely do not think that blockchain

is a centralized database here this is

just for representation

what you can do is you can share your

information your medical history on the

blockchain and you can provide access to

anyone who wants to have a look on that

data so let's say you have a key and you

have locked that key on the blockchain

and the beauty of blockchain is that

once your data is there it is there so

it will not be erased or manipulated it

will always be there and let's say in

the case of prices you can transfer your

keys to uh let's say in this case City B

and CTB then can go and unlock your

medical history documents and can see

your data and can provide you a good I

will say good treatment right so that

you can recover fast

so this is also one of the applications

of blockchain and this is also getting

so much I will say popular and I think

in near future we are going to see this

a lot okay so we discussed four

applications of blockchain right in the

international wire system

Health Care System smart contracts and

product tracking right

but definitely there are various other

applications of blockchain and now this

is your homework okay you have to

comment below and you have to tell me

what are other applications of

blockchain okay you have to tell me like

what other places blockchain can be used

and let's other also know that what are

the other applications of blocks in and

I will be waiting for your homework so

please do not forget to do that okay now

let's talk about hashing algorithm

because this is the term you are going

to see a lot you will hear a lot when it

comes to blockchain so let's talk about

this

what is a hashing algorithm

so if I will show you a block of the

blockchain this is how a block of the

blockchain of a blockchain looks like so

we can see that these are the different

blocks connected with each other and

this single block looks something like

this definitely there are various other

fields also but for demo purposes I am

considering four fields for now that is

block number like at which number this

block is present so if you will see that

in this case this is block number one

block number two block number three then

we have data data means transaction so

let's say if a is doing some transaction

to B that transaction will be noted here

if C is doing some transaction to D that

transaction will be rotate here so each

and every data is present in this data

field then we have this previous hash

which we will talk in our upcoming

slides and then we have this hash okay

now this is very important what is this

hash all about uh right zero zero zero

some alpha numeric characters you can

see on your screen but what is the

meaning of this alphanumeric characters

so this hash that you are seeing here is

actually

a unique identifier

to this block of the blockchain okay so

this is a unique identifier to this

block of the blockchain what do I mean

by that so every human being has a

fingerprint right and this fingerprint

is a unique fingerprint so no two human

beings can have a same type of

fingerprint okay I know this is

according to science okay so just don't

believe if you do not believe me just

search on it and you will see a lot of

scientific researches on this that no

human being can have identical uh thumb

Impressions or you know impressions of

your of your fingers and all

and the same thing happens in case of a

block of the blockchain so this hash act

as a unique identifier to this block of

the block shape so let's say

it is like giving a name to a block okay

so this is like a name given to this

block and with the help of this name I

can identify this block now why do we

need this identifier you will understand

it just uh in just up in our upcoming

slides and upcoming videos so just don't

worry about it

so this hash is acting as a fingerprint

to this block okay so this hash is

acting as a fingerprint to this block

and how this hash is actually being

generated like how do we how do we get

this hash so for hashing what we use is

a hashing algorithm so this sha-256 is a

hashing algorithm we have other hashing

algorithms also like we have kcat 256 we

have sha 512 nd5 there are various

hashing algorithms but in case of

blockchain most of the time we use

sha-256 algorithm okay now when we give

some input to this sha 256 algorithm

that input can be in document Audio

Video in any form this chart roof this

is algorithm convert this document audio

video Etc anything in a 64 digit

hexadecimal characters okay so if you

will calculate there are 64 characters

here okay and you have to trust me on

this or you can read this also it's up

to you

and why it is called sha 256 because

there are 64 hexadecimal characters one

hexadecimal character is of 4 bits and

that's how we have this 256 bits okay so

one character one hexadecimal character

is of four bits and each character is of

since there are 64 characters so 64 into

4 we have 256 bits okay what are

hexadecimal characters just searched on

Google you will easily find hexadecimal

characters just like an angular system

like that like we have a decimal number

system from 0 to 9 in the same way we

have hexadecimal number from 0 to F okay

that's why you are seeing these letters

coming up here okay

now in case of a blockchain what are the

inputs because as we have seen right

these These are the inputs to this chart

of D6 algorithm and that's how this is

actually being you know

generated now in case of blockchain what

are the inputs so in case of blockchain

these different fields that you are

seeing on the screen act as a input and

these inputs are giving to this chart

with Basics algorithm and this chart of

this x algorithm then produces this hash

and remember one thing this is a very

important point chart of physics

algorithm always and always produce a

unique identifier unique hash okay there

will be never a time where for two

different input you will have a same

hash okay remember this thing now let me

demonstrate you this chart with this

algorithm because I know many of you

might still be confused let me

demonstrate this in real life so here we

are on this side

just uh just type shot 256 generator and

you will be on this side and in this

side you can clearly see that we have an

input and this is our output let's say I

have written something let's say I have

written H so as you can see that as I

have written this H you can see that we

have a hash of 64 hexadecimal characters

and one important point that you should

notice here is a small change in the

hash not in this hash actually in a

small change in the input will

completely create like completely change

this hash there will be a totally random

hash which has nothing to do with this

Edge like let me show you let if I let's

say I have written a here now you can

see that this hash generated in the

previous case these two hashes are

completely different from each other now

this is one of the beauty of sharp

dresses algorithm because this is very

important characteristics of a good

hashing algorithm like for each and

every input we should have a entirely

different hash okay so let's say if I

have written anything I am writing

anything here you can see that never

ever never ever it is producing more

than 64 hexadecimal characters

whatsoever I'm putting here okay so this

is how short of this x algorithm works

and in case of blockchain as I said we

have the different input fields and we

use these input reports as an input to

this chart with physics helicopter

now definitely you might be thinking

like why I'm using the like why I'm

using nine characters here this is just

for demonstration purpose because I if I

am going to write the 64 hexadecimal

character it will be a large digit right

so for demonstration purpose I'm going

to use nine characters only but in

actuality remember sha256 produces 64

hexadecimal characters

now let's talk about some

characteristics of this hashing

algorithm because I know this is also

one of the important questions like not

question doubts like uh how like what

are you know what how what make this

chart of physics algorithm a good

algorithm why we are using chart of

disease algorithm why we are not using

any other algorithm so let's talk about

some of the good characteristics of us

hashing algorithm

so the final requirements that every

hashing algorithm must fulfill first is

that it should always be one way means

let's say you are giving a data to this

start to Basics algorithm and this data

is now converted into a encrypted data

because the hash that you are seeing on

your screen is actually working as an

encrypt editor right I'm writing H A or

something here and it is producing some

encrypted data of that

now the good hashing algorithm will

never

give back the data means you can produce

you can go from this data point to

encrypted data point means you can go

from this to this but you cannot go back

from encrypted to this means you can

generate let's say a hash from a given

input but from a given hash you cannot

generate the same input back so this is

one of the key requirement of a hashing

algorithm another thing is it is

deterministic deterministic means that

it always for every single input it is

going to give you the exact hashing hash

means let's say for one two three it is

producing producing some hash def so it

will always and always produce this def

whatsoever be the case if the inputs are

fixed means for

uh for you you will never see a

situation that for a single input you

are having two different hashes okay you

will always have the same hash when you

are giving when you are going to give

the same input so this is also one of

the beauty of this hashing algorithms so

ABC so let's say yeah I have given

example also ABC produces the hash of

845 so always and always ABC will

produce the same hash it will never

produce 849 or 948 okay third thing is

it should be fast definitely it should

be fast otherwise it will take if it is

taking a lot of time just for producing

these hashes then it will be a time

taking process right

now what do I mean by with the sand

Collision means uh it should be very

difficult it should be very difficult I

think I will say exponentially difficult

to have the same in to have the same

hash for the two input means it should

never happen the probability of

happening that we have two inputs two

different input and these two inputs are

producing the same hash it should be

very very very less it should never

happen that two inputs are actually

producing the same hash okay so it

should withstand collisions and last

that there should be a Avalanche effect

if launch effect what do I mean by that

as we have seen in our uh chart 236

generator right calculator you you might

have seen that even I am changing a

small alphabet there there is a complete

new hash for H we were having a

different hash for H A we were having a

complete new hash right now that is what

we call Avalanche effect so that each

and every time you are even if you are

making a single change in the input you

will get a complete pretty different

hash okay hi now in this video we are

going to see how actually blockchain is

formed using hashing algorithm so in the

previous video we talked about hashing

algorithm right sha-256 hashing

algorithm where we discuss that for each

block we have a unique hash right now

let us understand how a chain is formed

between two block of the blockchain so

let's say we have two blocks here

this block in green and this block in

blue so this is block number one and

this is block number two right and this

block has this hash of this like zero

zero zero d8c42 and this block is having

a hash of zero zero zero three four five

uh three a four five nine right so this

is the identity of this block and this

is the identity of this block

now how these two blocks will be linked

together so that they can form a

blockchain right because as we discussed

in our blockchain video that blockchain

is nothing but it is a chain of blocks

so now we have two blocks let's see how

they are connected with each other so

now let us see how these two blocks are

linked together

so here you can also see that we have

one more field that is a previous hash

in block number one as well as in block

number two for block number one previous

hash is zero zero okay why because this

is for the Genesis block since this is

the first block of our blockchain so we

call this block as a Genesis block and

in this previous hashes nothing okay but

in this case in block number two this

block number two also have this previous

hash feed now this previous hash of this

block number two will consist of the

hash of this block number one so if you

will see it is zero zero zero zero d8c42

and this is also zero zero zero d8c42 so

with the help of this hash of block

number one this block number two is able

to identify block number one by having

the hash of block number one in its

previous hash okay and I think this

makes sense because this is a unique

attitude to this block so this is like

this block number two is calling this

block and that's that's why we have this

link now let's see if a block number

three is created in that case this block

number three will have a previous hash

equal to the hash of block number two

and with the help of which block number

three will be able to identify block

number two and there will be a link

between these two blocks and this is how

a blockchain is formed in in a

blockchain system I will say and this is

our Genesis block as I said

hi now in this video we are going to

talk about why blockchain is immutable

definitely when we discussed about the

definition of blockchain we discussed

that blockchain is a distributed

immutable Ledger right now let us see

why blockchain is immutable with the

help of an example so let's say this is

you okay who wants to buy a house okay

now in order to buy this house

definitely you require money as well as

you need to sign a contract with the

party with the with whom you are buying

this house right so let's say this is

this house is belonging to party B and

now you want to buy this house from this

party B so you need to sign a contract

right and now you will take this sales

deed contract and present it to the

government so you will go to the

government officials saying that okay

this is a contract that I have signed

with party B and now this house this

house title belongs to me title means

for now you can think of it as the name

of this house for now just take uh just

assume that title is the name of the

house and you are saying that okay now

this house belongs to me since I have

given party B this money and now I have

all the documentations and everything so

now this house belongs to me so you will

present this these facts to the uh these

contract on facts actually you will

present this contract to the government

institution now after receiving this

information institution the government

institution will record all the

important information over a file over a

register or they can also use a

centralized database means they can also

use computer in order to so in order to

store all the information related to

your uh related to your contract related

to your title of the house

now the problem with this approach is

that anyone can change record of this

register right because this resistor is

nothing but uh government institution

has just written some uh data on a paper

so now anybody can change the record in

this register if we talk about

centralized database definitely in

centralized database since database is

centralized in nature anybody any hacker

can also make changes to this

centralized database or

the government of

or if the government is corrupted in

that case they can also make changes to

this centralized database and once this

is done you will be in trouble right

because this file this file is actually

stating that this house belongs to you

but if someone is changing the fact

someone is changing the information in

this file in that case this house will

not belong to you and there are so many

cases that has happened before and and

still these type of things occur where

the person who has bought this house has

no authority over the house just because

there was some mistakes given or there

was some changes in the government

documentation so you do not want to lead

up in such type of trouble right because

if you will if you will be in such type

of situation then your situation will be

like this right because you have

invested so much money in your house

so in order to prevent from this

situation what we can do is we can use

blockchain which is an immutable Ledger

so let's say uh this transaction this

data that you are buying this house is

stored on blockchain so this data is

stored on let's say Block C okay

and now someone hacked this Block C

because we are assuming that okay

blockchain can also we have someone is

trying to manipulate the data means

manipulate the data that this house

belongs to you in this Block C so this

hacker is trying to manipulate this

Block C since this Block C is containing

the data that the house belongs to you

now if the hacker will try to hack this

block trying to change this block data

the blocks that are after C will also

get affected why it's very simple if you

have watched my previous video where

where I discussed that the new block

consists of

the hash of the previous block right so

this D will consist of the hash of Block

C in its previous hash field similarly

for E and F right so once this block

will get corrupted the data in D E F

will also get corrupted right and if you

do not remember let me show you the

presentation from our previous slide so

here you can see that that this is our

block number let's let's assume that

this is our block number D this is not

this is a block number c someone is

trying to change the data in block

number c and if let's say someone is

trying to change the data in block

number c then the hash of this block

will change why because these different

fields are being used in order to get

this hash right and this also we have

discussed in the short V6 algorithm

video so this hash will get changed and

since this hash will get changed the

this this block number two that is our d

block is also having the hash of this

block right so if this will change then

this will change and since this will

change the hash of this will change and

since the hash here will change then

definitely again you can see the uh

domino effect here right now the

previous hash of this will change and

the hash will change so in this way the

all the blocks that are coming after C

will get changed and by this the network

the distributed network of blockchain

will know that there is some issue with

the blockchain as we discussed also this

right that our blockchain is our

distributed immutable ledger so if we

are assuming that this is our blockchain

okay this is our P2P network of

blockchain we will discuss about PTP

Network in our upcoming video but for

now this is our P2P Network right

and here you can see that this block is

getting affected now once this block

will get affected the people this this

block will also get affected and the

people who has the correct copy of the

blockchain will get to know that there

are some issue with the blockchain of a

and what they will do is they will

correct these changes because they have

the correct copy of the blockchain okay

and this is why blockchain is immutable

in nature right so this is why

blockchain is immutable in nature

because if you are going to change any

block this change in one block will

affect the rest of the blocks now some

of you might be thinking that what will

happen if someone tries to change the

first block right and we will talk about

this case also in our upcoming videos so

don't worry about it and yeah this first

and last block calls right so don't

worry about it we are going to talk

about this in our upcoming video because

this is a concept which is not not which

is not the part of this video but now

for now you have must have understood if

someone tries to change the data of

middle of the block or the blocks that

are coming in between some blocks in

that case how immutability will take

place in blockchain hi now in this video

we are going to talk about P2P Network

now this is a term that I am using a lot

so let us understand P2P Network and in

order to understand P2P Network let us

first understand what is a centralized

Network and how it works okay so in a

centralized Network we have two parties

one is server and another one are

clients so as the name suggests by the

server server is a one who serves the

client okay and this server is actually

holding all the data so you can

understand this with the help of an

example uh that YouTube is a company

that has its own server which on This

Server all the videos are stored okay

and when someone wants that video when

someone wants that data they request

from YouTube server and then YouTube

server provide them with that data now

in the case of this like if you will see

this diagram this picture that is

appearing on your screen now in case of

this you as you can see that this server

is holding some data right and let's say

this client wants this data from the

server okay so what this client will do

they this client will actually request

from this server that okay I need this

data that you are having and then server

will responds to this client with that

data now this is how a centralized

network works okay let's say if this

client wants some data it will request

from the server and then the server will

respond with the data that the client

has requested and in the same way other

clients also can do that now the problem

with this approach is that if someone

hacks the server

then this data

will get manipulated right because the

someone is hacking the server and let's

say uh the hacker made some changes to

the data now in this case if a client

requests data from the server in that

case the client will have this

manipulated data right so the data will

not be a right data so the client will

be getting some manipulated data so this

type of situation we do not want right

some of the let's say it's some it is

something very important to us it is a

very important file and now we are

getting some corrupted data just because

a hacker has a hacked this particular

server so what we can do is we can use a

P2P Network now what is a P2P Network so

in a P2P Network we have peers okay PE

stands for peers so this is a p

peer-to-peer Network now in a

peer-to-peer Network there is no server

there is no client okay everyone is at

equal position so anyone in this whole

network can share data and anyone from

this Network can request for a data okay

so each and every one is at same level

there is no server there is no client

each of them are or you can think like

this also that each of them are server

and each of them are clients also okay

so let's say and now a wants that data

from B so a can request that data from p

and in let's say another case that e

wants the data from a so e can also

request the data from a right so in this

way P2P network works right it's a very

simple process anyone from this uh P2P

Network can request data anyone anyone

from this network can produce data so

there is no client server there is

nothing like that okay each and everyone

are e at equal level okay so this is

what P2P Network looks like and this is

how blockchain network is formed where

each and everyone is having the exact

copy of the blockchain and each of these

people can talk to each other via P2P

Network now let us also see that how P2P

Network distributed P2P network works in

blockchain also okay so this is our P2P

Network in our blockchain and let's say

a block is added at is end okay so a has

created a block how it is created we

will talk about in our upcoming videos

but let's say a has created this block

okay now once a has created this block a

will send this information to its

peers okay which are b e and f in this

case so a will transfer this information

to b e and f saying that okay I have

created this block

now once this is done b e and f will add

this block after verifying and

validating whether the block is correct

or not if the block is correct then they

will add this block to their blockchain

now after this b e and f will transfer

the same information to C saying that

okay we have a block that is created by

a can you check whether it is right or

not so c will take this block he will

also verify and validate this block and

if this block is correct then C will

also add this block to its blockchain

and this is how P2P network works in a

blockchain right because each and every

one can talk to each other each and

every one are at equal level so each

people can talk to each other in our P2P

Network

now you must be thinking why do we India

why do we need a distributed P2P Network

in blockchain so as we have discussed in

our immutable Ledger video right if

someone tries to manipulate a data so

all the data will get corrupted right

all the blogs that are coming after that

particular block will get corrupted so

we have discussed about this right and

to convey this information what we need

is a P2P Network okay I have this text

here right so I have removed that so now

let's say if a block is get corrupted in

one of the blockchain okay so let's say

a hacker has hacked a system and now he

has manipulated the this block of the

blockchain now this information will be

transferred via P2P Network only okay

and you can also see that once this

block is get corrupted all the remaining

blocks or the blocks that are coming

after this block also get corrupted

because of the hashing thing right

now this information will be transferred

to b e and f d e and f will check okay

now the block that is the block that a

is having and the blocks that we are

having are different blocks so what they

will do is instead of adding this block

to their blockchain they will correct

the block of a saying that a you are

having a wrong block let me correct this

block okay so this is how P2P network is

very essential in order to maintain this

immutability in our blockchain Network

okay so I hope now in this video we are

going to talk about a very interesting

topic that is blockchain mining

now this is one of the most interesting

topic of mine also let us see this and

in this video we are going to just see

an overview in our upcoming videos we

are going to see a detailed uh video

about blockchain mining like how

actually it is done but for now let us

see an overview and trust me you will

love it okay so let's say uh someone is

doing or let's say you are doing some

Bitcoin transaction okay so you are

doing some Bitcoin transaction

now this Bitcoin transaction will go to

a pool of miners okay we have pool of

miners here pool when I'm saying pool

means there are so many miners uh

present in our blockchain Network okay

so once they will see the okay the

transaction is done they will take this

transaction

and they will try to add this

transaction

on a block of the blockchain okay and

the block can have multiple transactions

or thousands of transaction or depends

upon the depends upon blockchain to

blockchain but let's say for Simplicity

that in this blockchain a block can have

only one transaction but a block of a

blockchain can have multiple in for the

Simplicity of this uh video I'm going to

say that uh block can consist of only

one transaction so once the miner will

see that okay a transaction is done so

they will see this transaction and they

will start solving a mathematical

problem why they will solve this

mathematical problem they will solve

they will start solving this

mathematical problem so that they can

add this transaction on the blockchain

okay so that's why they will start

solving the mathematical problem

now The Miner who will solve this

mathematical problem first okay because

there are so many minors and let's say

one of these minor let's say this minor

has solved this mathematical problem

first

now once he will solve this mathematical

problem first he will be able to create

a block having this transaction okay and

after this process means after this

block is created

this block will be verified and

validated by other set of miners mean

others that means that the my this Miner

will not be a part of this verification

and validation but all the other miners

will start verifying and validating this

block whether the block created by this

Miner is a correct block or not okay

whether this blog is not this block is

not a many is this block is a malicious

block or not okay

if this block is a malicious block then

they will reject this block and they

will not add this block to their

blockchain and hence again the process

of mathematical problem will start means

again the miners will start solving the

mathematical problem so that they can

add this transaction but if this block

is correct if this block has no issues

in that case what they will do they will

add this block to the blockchain to

their blockchain we have seen this also

in our distributed video right where we

talked about blockchain they will add

this block to their blockchain and the

miner who has solved this mathematical

problem first will be rewarded with some

cryptocurrencies okay and this block

will be added to the blockchain and this

is how the whole mining process works

now you must be having questions right

like who can be the miner anybody can be

the miner okay you just need to solve

you just need to install a software

let's see if we talk about blockchain

Bitcoin client once you will install

this software you you will have an

option in order to like you will have an

option to be a minor thing okay and uh

let me tell you one thing more that

verification and validation is not just

done by the miners verification and

validation is also done by all the nodes

okay there are other systems also apart

from Miner who are just doing

transactions who are just part of that

blockchain Network they will also they

can also verify and validate your

transactions so only miners are not

verifying and validating other nodes set

up that are connected to this blockchain

network also verify and validate this

transaction okay

this blog what do I mean by that okay so

this is how blockchain network is this

is how actually blockchain mining is

that not blockchain network but this is

how blockchain mining is done now what

is this mathematical problem you this

can also be one of your question and

don't worry we are going to talk about

this in our upcoming videos where we are

I'm going to talk about nonce which is a

very important topic uh which is a topic

that you will face a lot in your

interviews also so we will discuss about

that in our nonce video but for now I

hope this is very much Clear what is

blockchain mining and how it is done hi

now let us talk about a very important

problem in our distributed Network that

is byzantines General problem

now in a Byzantine journalist problem

let us understand this with the help of

a story okay this is very important

problem you must understand this problem

so this is our Byzantine Kingdom okay

our beautiful Byzantine Kingdom

and there are four Army generals of some

different Kingdom okay and these are

like these four Army generals belong to

the same Kingdom and they want to attack

on this Byzantine okay they want to

attack on this Byzantine they want to

take over this Kingdom

now in order to attack on this Byzantine

and in order to win this Kingdom because

Byzantine definitely will also have its

Army right so in order to win from

Byzantine

they need to be attacking at the same

time means majority of these generals

need to attack at the same time in order

to win over Byzantine okay

and we are we are assuming that we are

assuming that all these Army generals

are at different locations so let's say

this Army journal with its Army is at

North this is at South West and East

okay so all these Army generals with

their army are at different location

now definitely since they have to attack

at the same time they need to

communicate with each other right then

only they can attack at the same time

when they have the information that okay

this Army General is going to attack now

we can also planning let's plan to

attack right so they need to communicate

with each other but the problem is that

they are at different places

so what they will do so they will send

their messenger saying that whether to

attack at this point of time and or

whether not to attack at this point of

time so let's say this Army General okay

send this information to the other rest

of the army General that okay this is

the best time to attack on Byzantine I

think this is the best time let us

attack on Byzantine now the same thing

will be done by the rest of the army

generals they will also send their

Messengers they allow this Army General

has sent this information okay this is

the best time let us track on Byzantine

uh present time uh Byzantine Kingdom

okay other kingdoms will also like other

kingdoms not other Kingdom other Army

journals will also send this information

and this Army General will also send

this information via their messenger

that okay let us attack on Byzantine and

this is an ideal situation and if this

will happen then definitely they will

win Byzantine Kingdom because now they

are attacking at the same time majority

of them are attacking at the same time

so definitely they are going to win in

Byzantine Kingdom right

but what will happen if one of these if

one of these Army generals is a traitor

right this can also happen that this is

a traitor now this will be a problematic

situation why because the stateral

trader will give wrong information right

so let's say that all these Army

generals are saying that to attack is

the best like this is the best time to

attack on Byzantine because they will

win over byzant time if they will attack

at the same time at this particular time

but this since this Army General is a

traitor he is sending false information

to the rest of the generals that okay no

this is not the best time to attack

let's not attack at this point of time

because he's a traitor even though this

is the best time to attack he will say

that do not lets do not attack or at

this point of time

so what will happen in this case now in

this case

these Army generals will go for the

majority of the votes okay so this Army

General will see that okay what is in

majority to attack or not to attack and

he will see that okay this Army General

is saying to attack this Army General is

same to attack so and this is the only

Army General who's saying that this is

not the best time to attack so

definitely he will go with these two

Army Generals in the same way he will

also see that okay this is saying to

attack this is saying to attack but this

is saying not to attack so let's go with

these two people since these two people

are in majority in the same way he will

see that these two people are a majority

and they will attack and they will win

over Byzantine once again now why I am

telling you this story because this

story is if you will relate it to our

distributed Network where distributed

Network are present at different

location and they need to verify a

particular set of information now in

order to verify a particular set of

information these distributed system

depends on the material Authority

and same goes for our blockchain network

blockchain network is also a distributed

P2P Network right we have also seen in

our we have seen in our previous video

right so in a distributed P2P Network

definitely there can be some Traders

there can be some hackers who will send

you some wrong information so in that

case our distributed P2P Network totally

depends upon the maturity

if the majority of the people are seeing

something we are going to assume that

that is correct if majority are saying

something that that like majority are

saying that okay this is not a correct

information we are going to assume that

this is the correct means we are going

to assume that the majority is correct

in this regard also so this is how

distributed P2P network works but now

definitely there is one problem now you

must be having this question in your

mind what if if majority of the people

are hackers what will happen in that

case like in this case definitely if you

will see

three-fourth of the people that is 75

percent of the people are correct right

50 75 percent of the people are the

right people

but only one-fourth means this traitor

is the person who was sending some wrong

information so India's in this case this

is correct but what will happen if 50

are seeing something and 50 are seeing

something what will happen in that case

in that case your distributed system

will fail yes this is the truth your

distributed system will fail but the

probability of happening that is very

low the probability of happening that is

very low because just uh just use your

common sense right here that how there

can be 50 hackers right how let's say if

there are lacks of people connected in a

blockchain network how there can be 50

000 hackers this is not a possibility

right only I think 10 000 of the people

will be hackers or let's say one

thousand people will be hackers right we

cannot see we cannot say that 50 000

people can be hackers because the

probability of having is low definitely

they it can happen in future but the

probabilities of happening is is very

low right so now I hope you understand

what is Byzantine General's problem

right and correspondence to our

distributed computing where distributed

computers distributed computers are all

over the network so in order to verify

and evaluate a particular information

they need to depend upon the majority

okay and this is the only solution to

our Byzantine General's problem now in

this video we are going to talk about

consensus protocol so let's start before

talking about consensus protocol let us

understand the concepts that we have

learned so far so we have talked about

hashing algorithm and its importance in

order to create a blockchain immutable

Ledger which protects our blockchain

from hackers miners who actually verify

validate create R blocks in the

blockchain and then distributed PTP

network with the help of which we

distribute our block all over the

network right

now what is the importance of consensus

protocol let us understand this

consensus protocol helps us in two ways

first in order to prevent attacks like

if some some hacker is trying to attack

our blockchain in that case it helps us

and then in competing chain problem

which we will see in the next video in

this video we are going to talk about

how it prevents attacks

so there are various type of consensus

protocol you might have heard these name

proof of work proof of stake and there

are others also like proof of concept

proof of history there are so many other

consensus protocol but in this video we

are going to mainly talk about our proof

of work consensus protocol okay

so let us understand this

so as we have discussed in our immutable

Ledger video If a hacker tries to

manipulate any Central block or any

middle block of a blockchain then all

the blocks after that block will get

affected right and by this these other

nodes that are part of this blockchain

network will be able to identify that

there is some mistake with this is

blockchain and they will correct it but

what will happen if

a is a hacker who is trying to add a

malicious block at the end of our

blockchain now in this case what will

happen because now there are no other

blocks right after this there are no

other blocks with the help of which we

can say that okay this block is not a

right one or is this block is not a

correct one because b c e and f you can

clearly see that they have only four

blocks while a has added this corrupted

block but bcef do not know whether this

block is a correct correct block or not

now how we can prevent from this type of

situation now in order to prevent from

this type of situation what we have is a

consensus protocol so before adding this

block this malicious block to their

blockchain like bcef in their blockchain

a consensus protocol is run this

consensus protocol makes sure that the

block that is being created by a is

correct or not so there is an algorithm

so you can see that this is this is some

part of the algorithm there are

definitely it is a three to four

documents long algorithm but I'm just

showing you some part of it so this is a

consensus protocol that runs whenever a

new block is added to the blockchain in

this consensual protocol the person who

is adding a block he has to present a

proof he has to present a proof that the

block that I am adding is a correct log

and that's why this algorithm is also

known as proof of all calcium in case of

Bitcoin because the person who is adding

this block he has to present a proof by

stating that okay I have worked on this

uh this block I have involved on this

blog in order to add it and to what is

what is that proof like let me tell you

that proof is uh like the amount of

energy this a is consuming in order to

create this block because in a proof of

work algorithm a lot of energy is

required a lot of power is required and

why this is so we will see in our

upcoming videos but a lot of energy is

required in order to create this block

so a will present a proof that okay I

have consumed this amount of energy I

have consumed this amount of you know

power in order to create this flow and

definitely there are other checks also

which will also run in order to verify

that the block that is being created by

a is a credit block or not now once this

is done then and then only this block

will be added to other nodes of the

blockchain

and then only a will be rewarded with a

cryptocurrency if this consensus

protocol this proof of work protocol

finds out that this block added by a is

not a current Block in that case it will

not be rewarded with any cryptocurrency

and a will be at loss because a has to

consume huge amount of energy let's say

he has a consumed use amount of energy

in order to create this malicious block

then he has to pay a huge amount of

electricity bill so a will be at loss so

this is how our consensus protocol Works

in order to have correct non-malicious

block okay so if a block is added at the

end of the blockchain also then also we

have mechanism to prevent from a block

which is malicious in nature now there

can be a question that verification and

validation like since this adding of

blockchain this is adding off a block in

a blockchain takes a lot of time okay it

takes around an average of 10 minutes

but does verification and validation

also take that amount of time because e

b c e f will also verify and validate

this blog right definitely consensual

protocol will run but also BCF will also

take measures in order to verify and

validate this block so is this

verification and validation is is this a

time taking process so no this is not a

Time tracking process creation of a

block is a time taking process but

verification and validation is a very

easy process it's like you are giving a

ux who like you have like I have given

you a problem you have to solve this

Rubik's Cube and anyone right anyone

from the network can identify that

whether this Rubik's Cube has been

solved in a correct way or not right you

can just look at this Rubik's Cube you

can turn around and you can see that

okay this Rubik's Cube is has been

solved in a correct way but to solve

this Rubik's Cube is our actually time

taking process and solving this Rubik's

Cube is like creating a block and to

identify whether this Rubik's Cube is a

correct one or not whether the Rubik's

Cube has been solved or not is

verification and validation which is a

very easy process as solving a Rubik's

Cube hi welcome to the second video of

consensus protocol in this consensus

protocol video we are going to talk

about the other use of consensus

protocol so in the previous video we

talked about prevent attacks how can

this is a protocol help us in preventing

attacks from the hackers now we are

going to talk about competing chain

problem let us understand this with the

help of an example so this is our

blockchain Network right and let us say

a

as well as C created a block at the same

time this type of thing can happen a can

pick a transaction okay so to become a

transaction there is a place called

mempool which we are going to talk about

in our upcoming videos but for now

mempool is an area from where a has

picked a transaction C has also picked

the transactions from the from this

mempool and they started solving a

mathematical problem and now they have

solved this mathematical problem at the

same time this type of thing can happen

because all these people are at

different part of the world and they are

competing with each other right so it

may happen that a has solved a

mathematical problem at the same time

when C has solved the mathematical

problem so now a is having a different

block and C is also having a different

block right now what will happen after

this after this evil and c will transfer

this information to its nearest nodes

right we can we we say the system at

nodes in blockchain terminology we call

these systems as nodes or you can say

system also but we call them as nodes in

a blockchain network so c will transfer

this information to B that okay I have

created a block a will transfer this

information to F and E that okay I have

created this orange block okay now like

why I am assuming that c is transferring

this information to B and not to E and F

we are assuming here we are assuming

here that uh for c b is the close B is

the closest node and for a f and E are

the closest node okay so that's why a is

able to transfer this information first

to F and E and C is able to transfer

this information first to B since C is

close to B okay so this is a assumption

we are taking here

now once this transfer of information

will be done then what will happen F and

E will create a block at their own end

means they will verify and will date

this block and they will see that okay

this block is good so they will add this

block to their blockchain in the same

way B will also verify and validate the

block of c and it will say okay it is

good so he will also add this block to

its blockchain okay so this is how our

blockchain network will look like

now the problem will arise is when b and

c will transfer this information that

they have a block purple color block and

a e and f should add this block to their

blockchain and AEF will also do the same

they will also this transfer this

information that they have created a

block they have added this Block Orange

block and they will want that B and C

should add this block to their

blockchain so information will it will

look something like this where B is

transferring this information to A and C

is transferring this information to E

and F where E and F are transferring the

same information to C B and all this is

how the transfer of information will

take place and this is not good because

now there is a conflict right so now

which blockchain block should be added

whether B will add the block of a e and

f that is orange block or whether a e

and f will add this purple block now the

question arises right now according to

our consensus protocol which so ever

network will have the longest blockchain

remember which so ever network will have

the longest blockchain that blockchain

will be adopted and the blockchain that

is having the short blockchain that

blockchain block will be discarded and

you will understand this with the help

of an example so just don't worry in

this case if you will see a enf are part

of a network right since they are close

to each other and they have the same

block so let's say that a e and f are

the part of our Network and B and C are

part of a different network

and we are assuming that each of these

systems that are present in our

blockchain Network have the same power

to solve the mathematical problem right

as we discussed in our mining video

right that all these people solve a

mathematical problem since they are

minors so we are assuming that each of

these systems that that is present here

that are present here are having the

same same power to solve the

mathematical problem okay

now since a e and f are a network and

they are in majority so they will have a

computational power of solving a

mathematical problem of three right

because one of this one of we are

assuming that uh this having a problem

this has the capability of you know

solving the mathematical problem of one

this is also having the mathematical

solving the mathematical problem

capability of one this is also having

one this is also having one this is also

having one so the whole network have the

capability like a e and f have the

capability to solve the mathematical

problem of three right in the same way b

and c will have uh the computational

problem to solve that mathematical

problem of two okay so definitely a e

and f are more powerful in in this case

right

so what AEF will do they will add

another block to their blockchain so in

this case we are assuming that e has

added e has created a block and E has

added this block to its blockchain now e

will transfer this information to a and

F and they will also add this block to

their blockchain now in this case if you

will see in this case if you will see

which of these which of these Network

have the longest chain so you can

clearly see that a e and f have the

longest chain right they have one two

three four five six blockchains means

six blocks in the blockchain while B and

C has have only five blocks in the

blockchain right

so as we discussed according to our

consensus protocol we will only respect

we will only consider the longest

blockchain and we will discard the

blocks of our small blockchain now in

this case since AEF has have the longest

blockchain so B and C blocks will be

discarded so the purple block that B and

C has created will be discarded so the

transaction that were present in BNC

blocks right in the purple blocks they

will be again transferred back to the

mempool okay mempool is an area where

all the transactions are kept so this

these transactions that are like these

blocks the transactions that are

discarded for now these blocks that are

discarded for now all the transactions

of these discarded block will be again

added back to the mempool so that again

mining can be done on them so that again

those transaction can be you know can be

processed in a block okay

so these blocks that you are seeing on

your screen these blocks are actually

called orphan block these are called

orphan block or you can say them as

discarded block now once these blocks

will be discarded BC will add the blocks

these orange blocks that are being at

that that are a part of this a e and f

Network so b and c will add these blocks

to their blockchain so that a

consistency among all the people of

these blockchain network of this

blockchain network can be maintained and

these blocks again as I said these

blocks will be called as orphan block

and these blocks will be discarded all

the transactions that were present in

these discarded block will be again

added to the mempool so that again those

transaction can be processed by the

miners in the next mining process okay

and this is how our

blockchain network will look like so

just remember always and always the

longest chain will win always the

longest chain will and the shortest

chain the block that the blockchain that

is having the short chain right in that

case the blocks will be discarded like

as we have seen in this case okay if you

are finding it a little bit complicated

just rewind back this video you will

understand it I guarantee you okay

so this is how our network will look

like a beautiful blockchain Network now

let us see some of the important points

related to our consensus protocol so the

consensus protocol of blockchain is much

better alternative to our Byzantine

fault tolerance what is a Byzantine

fault tolerance as we discussed in our

Byzantine a generous problem right in

our Byzantine General problem for that

General problem our solution was

proposed and that solution was this

Byzantine fault tolerance and for our

Byzantine fault tolerance the majority

of votes that we require is of 66

percent okay while in case of our

consensus protocol we only need majority

of 51 percent so our consensus protocol

is a much better alternative to our

Byzantine fault tolerance because fault

tolerance requires a majority of 66

percent vote while our consensus

protocol only requires 51 percent second

all the transaction in the open block

will be dropped as we have seen also

these transactions will again go back to

the member pool so that the miners can

again solve for it and the miner that

had mined the block right uh if you will

remember that c has created that purple

block right so that purple block was

discarded from the blockchain network so

for that she will not be getting any

type of reward because that block got

discarded from the blockchain network by

the consensus protocol so remember this

point also and third point is

for this type of situation if you might

have heard this thing that for for

whenever you do a Bitcoin transaction

you must wait for six block confirmation

and the reason for this is this only

that there can be conflicts in the

blockchain network so you do not want to

be the part of that conflict right let's

say a has transferred you some Bitcoin

okay now you are thinking that a has

done this transaction and now you will

be receiving the Bitcoin but after some

time the block that was having that

transaction got discarded from the

blockchain network because that block

was the orphan block right that block

was not a part of the longest thing so

it was discarded from the network in

that case you will not be getting any

like Bitcoin from a right so you must

wait for six block confirmation and then

and then only you should be you know

happy that okay now you have received

the transaction but we will talk about

like this six block confirmation more in

our upcoming videos this is just to give

you an you know overview of this that

why you should wait for six block

confirmation whenever you are doing any

Bitcoin transaction hi not only in this

video we are going to start with what is

bitcoin and why do we need it but let me

remind you that this is the starting of

our second module and that is

cryptocurrency so in the starting only I

told you right that we are going to

divide our course into three modules and

this is the starting of our second

module which we are going to start with

what is bitcoin and why do we need it so

let's start

so we are going to understand the

history of Bitcoin we are going to

understand why why do we need Bitcoin

what is the problem with our current

Financial system okay so let's start

with this

so all these things started in year 2008

when U.S economy was very bad nearly 9

million people lost their job and nearly

1.8 million small businesses got closed

and not only this Wall Street of USA

stock market of USA you can think of it

like that was on its knees

and the greatest Bank the biggest bank

of USA Lehman Brothers Bank are well a

billion dollar valuation bank got closed

during this period of time in USA and

you can understand the impact of that

situation by this picture where people

were revolting against the government

people were revolting against the banks

because they have lost all their savings

because they the people who are just

going to retire they have lost all their

retirement money people who were who

wants one who want who were saving for

their child education has lost all their

money child education money people who

are going to buy home they do not have

any money left in order to buy home so

situation was very very painful at that

point of time

now you must be thinking why all these

things were happening and the reason for

this is Banks the banks of USA because

of the foolishness of banks U.S economy

was in such a bad situation and not only

this

the U.S government was supporting this

foolishness of banks right U.S

government was supporting these

foolishness of Banks and now let us

understand what these Banks were

actually doing as you all know Banks

make profit by lending you money right

so when they lend you money they charge

interest on it and that's how they make

profit now in year 2008 or a year before

that

Banks started lending money to people

who were not capable enough to return

back the money

now you must think why they will do that

like what was the reason for doing that

and the reason was simple greed

according to banks at that point of time

they thought that if we are lending

money to someone they will repay back

who will not who is not going to repay

back the money so they were lending

money to people or anyone who was just

coming to the bank and asking for loans

and these type of loans are called

subprime loans means when you are

lending money to someone who is not

capable capable enough to return back to

return you back the money so since they

lended money to people who are not

capable enough to return back the money

so after some point of time bank started

going into loss and that simple right

because they have lended money to people

who will not who are not capable enough

to return back the money so they start

having losses

now to prevent situation like these the

U.S government start sending money to

these Banks just imagine because of the

foolishness of Bank all these things

started

and U.S government were not was not

punishing them but rewarding them with

money they were lending them money they

were giving them money so that the banks

can operate in a proper way now you must

be thinking what kind of just is that

because of the banks we were we the USA

was in that situation and U.S government

is supporting that and yes that's true

this is the true story and after this

incident a question was raised question

that can we trust stock Banks can we

trust our government when it comes to

money matters and the answer was clearly

no and do not think that this was the

first mistake or do not think that this

this was just a mistake which has which

just happened for the first time no this

this is not something which has happened

for the first time if you will look back

to the history you will see that a lot

of time these type of things has

happened in the history also where Banks

and government were doing something both

of them got greedy or something and they

start manipulate they started

manipulating the money situation of that

particular country of that particular

area and at that time only and at that

time only when situation was so worse

when everything was getting destroyed at

that time only Bitcoin was born and who

is the inventor of Bitcoin Satoshi

Nakamoto now nobody knows who Satoshi

Nakamoto is whether he's a person with

whether it is a team of person whether

he is a male or a female nobody knows

anything about sadoshi Nakamoto but he

is the inventor of Bitcoin

now what is bitcoin right we have

understood like like why like what is

the problem with our current Financial

system it is

it is under the control of our

centralized authorities like Banks or or

governments now let us understand what

is bitcoin how it is different from

these banks these garments because these

are the people who are actually

controlling the money the they they

control the supply of money they control

everything related to money let us

understand how Bitcoin is different from

these uh money right these currencies

actually Fiat currencies actually

Bitcoin is a decentralized digital

currency without a central bank or

single administrator that can be sent

from user to user on the peer-to-peer

Bitcoin Network without the need for

intermediaries

so if you will look at this Bitcoin it

is decentralized

cryptocurrency decentralized what do I

mean by decentralization it means that

nobody is controlling the Bitcoin there

is no single person who has a control

over Bitcoin it is a digital currency

okay so currently the currency that we

have is a fiat currency which is

controlled by the government it is a

digital currency it does not require any

Central Bank or any single administrator

and it can be sent over a P2P Network we

have talked about a P2P Network right so

it can be sent from one user to another

using a P2P Network and it does not

require any intermittarius

and it uses a technology called

blockchain and we will see the

difference between Bitcoin and

blockchain in an upcoming video so don't

worry about it but for now blockchain is

a technology that is being used by this

Bitcoin

this Bitcoin uh cryptocurrency okay

so this is how

for a Bitcoin like this is how a Bitcoin

Network looks like where people are

connected with each other uh it is a P2P

Network right where you can see that

people are connected with each other and

people can transact cryptocurrency with

each other it is a decentralized

distributed Network so know anybody who

wants to send money and who anybody who

wants to actually send Bitcoin receive

Bitcoin can can happen over this network

now the question next question that you

might have in your mind that if we talk

about our fiat currency fiat currency

trust is based on our government if the

government of a country is well then the

fiat currency is also good right if the

government is is in an unstable position

then the Fiat this VR currency will be

worthless okay and we will see the

example of this also in our upcoming

videos but for now just remember that

the trust of rpr currency is actually

based on our government

but when we talk about our Bitcoin

when we talk about our Bitcoin the trust

is on these algorithms these

mathematical problems with the help of

which this Bitcoin is actually built

and don't worry you do not need to learn

all those mathematical things there is

no mathematical problem to solve I know

many of you must be thinking oh no it

doesn't contain maths no it does not

contain maths just don't worry about it

I'm just trying to tell you here is that

Bitcoin uses mathematics okay

and yes if you want to learn more about

this financial situation of us in 2008

how Banks how this type of situation

arise in USA because of the foolishness

of banks I will recommend you this movie

this is a great movie all these actors

are great actors so you must watch this

movie if you want to learn more about

and there might be this question also

can this mathematical uh equation can be

wrong or algorithm can be wrong so let

me tell you like 2 plus 2 is equal to 4

right it does not matter whether you are

doing two plus two equal two plus two at

in USA in India or in Brazil whatever

place you choose it is always be going

to 4 right in the same way this

mathematical equation these algorithms

that are used in order to build this

Bitcoin Works 100 percent all time okay

so you are not trusting this no any

single person or something you are

actually trusting this equation this

algorithm and this equation the beauty

of this equation is that it is totally

available open source you can read about

it so it is not something which is

hidden from you you can go and just type

Bitcoin GitHub repository and you can

see all the source code available there

okay and it is not that it has just

started it is since 2008 a lot of people

has have already seen this open source

code but if you are thinking look I

cannot trust this so just go and type

Bitcoin GitHub repository and you will

you can find all the documentations all

the mathematical codes that are being

used in order to build this Bitcoin okay

and this is how Bitcoin ecosystem looks

like we have a miner who solves the

mathematical problem in order to create

a block we have nodes nodes means though

these are the people who are actually

transaction transacting means these are

the people who are sending Bitcoin from

one person to another so this is these

are called nodes okay so the system that

you see are actually nodes okay I'm just

representing it with these person but

definitely these are actually computers

only your computers or your lab laptops

are actually working as nodes are those

laptops can also work as miners also

it's all it all depends upon the like

what do you want to be so you have to

install a software Bitcoin client

software and then you can choose either

to be a miner or you can choose either

to be a node if you have become a node

you will be doing regular transaction

very fine and validation validation of

the blocks if you will become a miner

then you have to solve the mathematical

problem then we have large mines right

and we will talk about these large mines

which are actually using the whole like

a group of miners are there who is

solving the these mathematical problem

in order to create the plot and this is

the mining pool means where group of

miners are you know these group of

miners are working together in order to

solve so these large manners are

actually these mining pools only so they

form a mining pool in order to uh do

this

in order to solve this mathematical

problem in order to create a block so

when we talk about blockchain right

blockchain is actually a technology

as we have discussed in the definition

of blockchain network right not

blockchain Network in the definition of

blockchain where we talked about that

blockchain is a distributed immutable

Ledger right so this is the definition

of blockchain if it is a technology

well we when we talk about Bitcoin right

Bitcoin is actually a protocol slash

coin not only Bitcoin we have other

protocols also like waves we have

ethereum and definitely other Protocols

are also there and all these Protocols

are actually using blockchain as a

technology okay now what are these

protocols Protocols are basically rules

like if we talk about in our web 2 world

in our internet world we have different

set of protocols we have HTTP protocol

we have TCP protocol we have UDP

protocol so they are different protocols

which defines like how we are going to

communicate over the Internet how the

file transfer over the internet will

take place so each and every things is

actually being done on the internet

using these protocols in the same way

for our web 3 world for our blockchain

world we have these different set of

protocols which defines how people who

are connected to the blockchain network

are going to communicate with each other

how many cryptocurrencies they will be

like you know how like how minor will be

ordered with the cryptocurrencies how

mine are going to solve a mathematical

problem all these things are actually

rules which are implemented in this

protocols okay

so for example you can understand in

this in this way also that technology

when we say blockchain blockchain is

just like YouTube okay YouTube is a

platform right YouTube is a technology

on which we can have different set of

videos so these protocols that you are

seeing right these are like your videos

so you can have different varieties of

videos different set of protocols uh

like different varieties of videos over

the blocks over the YouTube in the same

way you can have different protocols on

this blockchain technology

now let us see this more with the help

of an example so we are on the site of

blockchain.com Explorer so here you can

see that we have different blocks of our

Bitcoin blockchain so this is using our

blockchain technology so let me click on

one of the blockchain so let me show you

this okay let me open this in new tab

let us see this okay so this is how our

block of our blockchain looks like we

are going to talk about in great detail

about this in our upcoming videos but

for now just have a look at it so this

is block number seven five two two three

five three okay and this is the hash as

we discussed our blog consists of a hash

this is the height this is the miner

which is unknown currently this is the

fee reward the amount the miners has