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hey what up guys welcome back to my

block chain channel and today we're going

to discuss the contents of a block in

the Bitcoin blockchain I think that the

block is very interesting is a very

interesting concept because the block

gives the blockchain its properties it's

the basic element of a blockchain and

therefore I think is important to

understand what a block game it consists

of

and also guys you have been requesting

ripple for a couple of days now and the

video about ripple is coming so stay

tuned we will talk about ripple in a

couple of days I promise you that but

today we'll discuss the contents of a

block so let's get into it

these are the basic parts of a block

first of all we have the magic number

the magic number is 4 bytes long and

it's an arbitrary number that signals

that this is a Bitcoin block so in

social development we have this notion

of magic numbers and different system

and different softwares use this number

to identify themselves and so Bitcoin a

Bitcoin client identifies itself as a

Bitcoin client by using this magic

number so that other systems and other

software software programs know that

this is a a Bitcoin block and that is

why we have the magic number and it's

just an arbitrary number and it is the

same for all blocks because all the

blocks identify themselves as a Bitcoin

block it's it's kind of like gender I I

identify myself as a man and all other

men on the majority of all other men

identify themselves as men not to get

political or controversial here so magic

number is is a number that identifies

what kind of software is is this and so

it's the same for all for all Bitcoin

blocks next we have the

block size which is also four bytes and

the block size tells us how how long

this block is with all of the

transactions next we have the block

header which is 80 bytes and the block

header is the most interesting part in

my opinion and we will talk about the

contents of the block header on the next

page that is why we have this arrow next

one is transaction counter which is an

integer that tells us how many

transactions this block has and next we

have a list of transactions which simply

contains all of the transactions that

are in this block and we have so if

transaction counter is 10 then we'll

have 10 transactions if the transaction

counter is 5 we'll have 5 transactions

and checks if the transaction counter is

from 1 to 9 bytes and locator is 8 bytes

blocks at is 4 bytes and magic number is

4 bytes as well so these are the basic

parts guys now we'll talk more about the

header so let's go ahead and look at

what the header consists of here we have

the header the header has a version

which simply tells us what version we

are on currently so for example the

current version of Bitcoin blocks is 2

and so if for some reason if a block

with version 1 comes it will be ignored

because the current version is 2 and if

in the future we would add more fields

and more data to this Bitcoin block

structure we would need to update this

version to a new version because now the

format of a block would look different

so this really identifies the format of

blocks because in the future we might

have blocks that look completely

different maybe we have will find some

new way of of building a blockchain

where the blocks look very different

from from this structure we have today

and then we'll have to change this

version

number two something else and the

version is four bytes

next we have 32 bytes of hash of the

previous block header so this is the

header and we can hash all of this

information at once and we get some hash

and so this hash previous block is the

hash of the header from the previous

block so we take everything here we hash

it and we have it as a filled hash

prayer block in the next block

so hash previous block is a hash of the

header from the previous block it's 32

bytes next we have hash of the merkel

root which is also 32 bytes and we

discussed miracle trees in my video

about blockchain so I link it in the

description you can go ahead and watch

it

and so in blockchain technology we have

this concept of Merkel trees and the

Merkel tree is a data structure where

each where each level of the tree is a

hash of the previous level you can go

ahead and take a look at Merkel trees on

Google or you can watch my video on on

blockchain and so hash miracle root is

the root hash of such a miracle tree

consisting guys consisting of the

transactions in in this block so we take

these transactions we put them in a

miracle tree in Merkel tree and we take

the root value and so we put it in the

header as hash merkel root next we have

the time which is the current times

timestamp it is 4 bytes next four bytes

is the target and I think this is a very

interesting variable because this tells

us the difficulty of this current block

and to understand how this works how the

target works when you turn this

understand how nonce word so when we

mine a block when the miner mines a

block what does the miner action

do what the miner does is he takes or

she

so they take this hash miracle route

they append a nonce which they guess

they start from zero and so they say

okay nodes is equal to zero

I'll guess that nonce is equal to zero

I'll append it to hash marker route like

this I'll take the hash I'll get a

number from that hash and I compare it

to target if yes if my my hash that I

received here from appending nonce to

hash maraca root if this hash is less

than target I am done and I have solved

the puzzle and I get the mining reward

however if it's more if it's higher than

the target I have to increase the nonce

so I increase it from zero to one i

append one here two hash mark merkel

root and and i append one I'll calculate

the hash once again this hash will be

completely different from the last one

I'll compare it to out and then I'll I

compare it to target and I see is my new

hash less than target if it's less than

target I'm done congratulations

and I'll get my reward however if it's a

higher than target I'll need to increase

this to two and do the same thing so

guys as you understand the lower the

target the more difficult is it to find

a hash that is lower than this target

one second guys so the Bitcoin network

automatically adjusts this target so

that each each ten minutes we get a new

block so if the Bitcoin network notices

that it takes five minutes for the

blockchain to mine a new block it will

decrease the target until it takes ten

minutes and if for some reason it takes

one hour to produce a new block it will

decrease this target so now we've talked

about version hash previous block hash

map merkel root time target and non

so nones it is basically the solution to

this puzzle so when a miner has solved

this cryptographic puzzle or which is

just guessing the gnomes up appending it

to the Merkel the hash of the Merkel

root hash mark root which is basically

like the element on top of the miracle

tree and if this hash is lower than bit

the target then the miner is done and

he'll get the reward however if it's

higher the miner needs to increment this

do the appended calculate the hash

compared to target if it's lower he p1

if it's not lower you need to increment

this so this is what we mean when we say

cryptographic puzzle it's not really a

puzzle it's it's a guessing game where

you just start from zero here you append

it hash compare if it's less you you're

done if it's not you take plus one and

do the same thing so as you can see it's

not a puzzle it's a very dumb puzzle

you basically just guess and so the

first the first miner that gets the

correct knowledge and calculates at a

hash that is less than the target will

win will win the game and he'll get the

reward so these are the parts of a block

guys we have magic number block size

block header

transaction counter and transactions and

now I want to I want to highlight the

beauty of of the blockchain and how its

visible in in the header because we have

hash previous block here which is the

hash of the previous previous block

header and guys if I wanted to mess with

the with history

if I changed something in them maybe in

the transaction from years ago as you

can see this this hash would be

completely different because the

previous block header contains the hash

that the hash mark Mercury

which is the top value in its in its

Merkel tree of transactions and so if I

change a transaction in the previous

block this hash mark the route would be

completely different in the previous

block meaning that hash previous block

in this block would be completely

different so let's repeat that if I

change a transaction in the previous

block previous block would have a

completely different hash mark merkel

root which in turns would give me in the

new block completely different hash

previous block and other other nodes

will notice that very quickly that the

hashes are wrong and so these two

variables really really give the

blockchain the property that you cannot

alter old values and you cannot mess

with the history and that is why I think

this is so fascinating you have hash

previous block and hash merkel root this

represents the contents of the preview

of the current block because this is the

hash of all transactions basically and

this represents the hash of the previous

block and so if you would change a

single bit in any of the transactions in

the current block or in any of the

transactions in the previous block this

this would be completely different and

if you change something in the current

block this would be completely different

and in turn the next block when we hash

this the next block would have a totally

completely different hash previous block

and so this is why we can't really mess

with the history when it comes to block

Chevy ice so that's it guys I am really

curious about your opinion this this

video was a bit technical I mean we had

bytes and we had different fields did

you like this or was it too technical

leave your comments in the comment

section below and and yeah please give

me feedback on my presentation did you

understand this it would

really interesting to hear and if you

are a new viewer and you like technology

you like blockchain you like Bitcoin

aetherium you should definitely guys you

should definitely subscribe because I

myself am a software developer and I

post videos every single day and you

will find them interesting so that is

why you should subscribe guys so today

we discussed the contents of a block and

I'll see tomarow.