Steemit Crypto Academy Season 5 Beginners' course - Homework Task 4: Blockchain, Decentralization, Block explorer by @habdallah

(1) Write the definition of blockchain. And how our data on Blockchain is protected from hackers. ? And write details about Data, Hash and Previous Hash tag and explain through screenshot.

(2) Define decentralization. Describe the advantages and disadvantages of a decentralized system. In what areas of life can a decentralized blockchain be helpful? (write in own words)

(3) What is a block explorer? And what is its purpose and use? Search for different cryptocurrency block explorers and list them below. At least five different crypyo currencies. Also explore the transaction of a crypto coin on block explorer and explain with the help of screenshots.

Definition of Blockchain

https://images.app.goo.gl/PfvNQSxCK98UtSm4A

Blockchain is an advanced technology that has a high level of security with a distributed database that is shared among the nodes of computers. Blockchain carries out and distributes data in a decentralized manner. That is to say the information or data is being viewed by everyone on the blockchain. Blockchain can be accessed with the help of a smartphone, and a computer. A blockchain can be said to be a distributed database shared among the nodes of a computer network only. Information on blockchain is stored in blocks. Every new block rises from a previous block. Each block of the blocks has three basic components. Which are data, hash, previous hash code. Blockchains are best known for their crucial role in cryptocurrency systems, such as Steem, Bitcoin and many more others. Which is being used for a secure and decentralized transactions.
One of the best aspect of blockchain is that it guarantees a secure and free management without the need for a trusted third party.

Blockchain technology is very secure and easy due to its decentralized nature (that is to say it is being monitored by every individual on the block). Blockchain is just like a distributor ledger, no information can be manipulated or changed on the blockchain.
On the blockchain, one can see all the history of a particular transaction that occurred on the blockchain. Due to it high level of security, it is impossible for hackers to hack into it. They are simply not able to hack into it because it is transparent.

Blockchain is said to be decentralized because, it can be accessed by anyone through online without having to ask anyone for approval or permission. But when you take a look at the banking system. It isn't like that, one will have to go to the bank as early as they can to take a queue number and join a queue, and patiently has to wait for their turn to be attended to. After which you will be asked for some documents. Without these documents you are likely not able for any transactions. Looking at this, you can see that we spend a lot of time at the bank as compared to using the blockchain. In this case blockchain is much more easier as compared to the traditional banking system.

Blockchain works as an online distributed system and is verified by thousands of nodes worldwide. Blockchain is a type of database that varies from a typical database in the way that it stores information in blocks. The data stored in a blockchains are linked together via cryptography.

How data on Blockchain is protected from hackers?

https://images.app.goo.gl/wgxPBVZhBAMTpCcw6

One might be wondering that is blockchain secure? Yes it is in the sense that blockchain technology gains decentralized security in so many ways. A new block is always stored linearly and orderly. Which is, they are always added to th end of the blockchain. After a new block has been added to the end of the blockchain, it is usually very difficult to go back and make any changes to the contents of the block unless a majority of the blockchain network has reached to an agreement to do so. One is not able to make any changes because each block contains its own hash, along with the hash of the previous block before it.
The Hash codes are created by a mathematical function that turns digital information into a string of numbers and letters. If that information is edited or changed, then the hash code will entirely change as well.

Blockchain is a decentralized digital ledger that is synchronized to all computer networks that are interconnected and works or depends on only one server.
This means that only the user can control the data. In case a users server goes down, the data from that user is still stored on another computer network.

Blockchain has the ability to protect or secure data with cryptographic hashes. Which simply means that data that has been entered or put into the blockchain network cannot be changed. But in case there is an additional data or other changes, the blockchain will still store the new data and the previous data will still be available.

A decentralized blockchain network can be helpfu in so many fields. A perfect example is in the voting or election field. Blockchain can be used to facilitate morden election system. Also it can be used for eliminating election fraud. Because it has the required potential.
Using blockchain in this way would make votes nearly impossible to tamper with. There will be transparency in the election using the blockchain protocol. It will provide fficials with nearly instant results.

The blockchain technology is safe from hacking attempts or data modification.
In case there is any attempt then all users will get an alert. If the hacker also wants to change the data, then he has to change the blocks, which is he will change block one, two, three and on because they are all intertwined and connected. This is almost impossible, because it will take a very long and complicated time.

Write details about Data, Hash and Previous Hash tag and explain through screenshot.

You will have to visit https://andersbrownworth.com/blockchain/blockchain to be able to check for your details.

Data

All information and data are stored in every block on the blockchain. All history about a particular transaction which is to say who the account belongs to, whom he is transferring the money to. The amount of money sent, to whom the money is sent to. Almost all the details you need to know about that particular transaction is available is termed as the data and stored on each block. Also no individual can be able to manipulate or make any changes to the stored data.

Hash
The hash varies from one particular block to the other with it special code. It does so by giving each block an identification number. It responds to every little change entered into the blockchain network. There by making it a very useful tool in the blockchain. It acts like a key to a particular lock. No other key can be used to unlock the lock apart from the specified key.

✓Previous Hash

Hash acts like a previous folder or file used for storing information. It contains the address of the previous block. Acting like an old file. Whenever data is filled in a block, a new block will be created to store the new information.
Not; the hash code of the previous block before the new block is put into the new bloc.

Previous hash blocks are linked to new blocks that make up the decentralized Blockchain.
Incase the hash of a block is changed, it results in a changed in the other block's hash, being it the old or new block. This happens because it causes the previous hash to be invalid.

Taking a look at block one and block two.

Block. 1
Nonce. 11316
Data.
Prev. 000000000000000000000000000000000000000000000000000000000000
Hashes. 000015783b764259d382017d91a36d206d0600e2cbb3567748f46a33fe9297cf

Block. 2
Nonce: 35230
Data.
Prev.
000015783b764259d382017d91a36d206d0600e2cbb3567748f46a33fe9297cf
Hashes. 000012fa9b916eb9078f8d98a7864e697ae83ed54f5146bd84452cdafd043c19

As we can see from the blockchain above, every block has a different nonce, data, hash and previous hash.
Let me try and fill in the blocks with some informations and see the results i will get.

So i typed in steem crypto academy in the block 1. After i typed in the info in block 1 all the blocks went invalid.

The nonce changed to 3147
Preview 0000000000000000000000000000000000000000000000000000000000000000
The hash of the first block also changed to this figures 0000ff81a80ed84c5fddb82bc58f88f6e0c38262dd8383363c051dc155139bce

The nonce of t block 2 changed to 56827
Preview 0000ff81a80ed84c5fddb82bc58f88f6e0c38262dd8383363c051dc155139bce
The hash also changed to 0000cc44768dac7ce90b462389026365e27bc9fc7d1db7bdf7660c0ca099b88b

After the above experiment i then typed in the same info into both the block1 and block 2.

Below was tge results i had after performing that experiment
The nonce of block1 remained the same but that of block2 changed to 21510
The hash of block 1 was the same.
Preview also the same.
The hash of block 2 was 0000f1b29ea6047b446057f4d28311a02c952520c42f2f8a4c86b5b4f63eb170

Block 2 didn't change, but the next block I changed the information, changed the previous Hash and invalid hash, as well as the nonce that didn't change (12937).
Preview 0000ff81a80ed84c5fddb82bc58f88f6e0c38262dd8383363c051dc155139bce

Conclusion
Blockchain is an advanced or high technology that has an extreme level of security and has a ledger where the ledger stores all digital data that is carried out and distributed in a decentralized manner. That's it is being viewed by everyone. It is connected to all nodes online and linked via cryptography.
The technology behind the blockchain is secure and transparent due to its decentralized nature. Therefore no hacker can tamper with it.
The information stored on block chain are all linked, that is all blocks has the same information.
Best regards @yousafharoonkhan