How secure is Block chain

1.Mining
Mining is an integral part of block chain technology. Some discussions have been discussed earlier. First let's know what the mining key is. Bitcoin is a powerful computer or other computing device that has the complete block chains of Bitcoin, which itself is actually open Haitian (Public Laser) and download the 'Betaken Core' software; Each computer or machine has a node. The owner of the node is actually miner. A miner may have some machines.
All Bitcoin information and software download links can be found on www.bitcoin.org. This site is registered with Satoshi Nakamoto. Miner must register on Bitcoin site. Miner should have a wallet so that if he gets a reward, then he can get his bitcoin deposited in his wallet.
Now a large number of people are mining, so to survive in this competition, there is a high-power computer requirement. First download the full block zipper. So there is a need to have good internet bandwidth. Bitcoin block chains are currently up to 20 gigabytes, but it is increasing daily CPUs are not being paid for mining, even GPU-which does not have much of its functionality. A special type of computer has been created for bitkayen mining, which is called 'esc', whose full name is Application Specific Integrated Circuit. This computer will do just one thing, that is mineing.
They use powerful tools and laptops or desktop computers, but at least use a GPU (graphical processing unit). But now it is no longer, if anybody else can solve the problem, then no reward or fee will be available. So now many people are making a mineing coalition (pool). It increases the chances of getting reward.
The mining software (Bitcoin Core) is actually doing mining work. Although its name is mining, it is not actually mining or extracting. Rather, it is a test conducted by conducting a transaction and certifying it. Many people will not be wrong in doing this. Then he has been 'hash' again, it will be thousands of machines. So there is no way to change or fake. Then working on solving a complex mathematical problem, which is called 'Proof of Work'. This Proof of Work can be completed before the machine comes to fight machine machine. Finally there is a prize for a winner, so there is no shortage of machines in combat.

2.Hash Function

Works with Block Chain Hash Function The hash function can make any small or big word or sentence equal to the length of time. Regardless of the length of the original word or sentence, the hash from the hash function will be the same length, its length is equal. Each transaction in Bitcoin is then synthesized by the hash function and then added to the block. Therefore, the hashtak or any cryptogram hash is important. SBH-52 hash is used in Bitcoin, which is the first row for cyber security. SHA-256 Discovery of the NSA (National Security Agency) in America. This hash function turns 256 signals into any word. The following is an example:
Bangladesh: 8 E 07 DF 26128 D8 A 78474 DC 525 BF0 F0 A 16 AFA 49344 E1 ED 4229692 E 13 B 313 DE 46 A8
Bangladesh: 2 F1 D 47 EB 679 BB 05 E6 D8 FE 039 AF 1563549588 CD 44 B 40 BE6 B 1013 EA8 CA 2268845 F
Dhaka: 50 FD 531 C 42 D3 E 81 F 37 A 89748 DFB4 F 55 E8 B 741390 BE 428449 A8 B9 BC 46582 FC 91 E
It is noteworthy that the second hash has only been different from the first hash in the first letter. That's why the data is slightly changed, but it will be easily caught in hash. There is no way to understand the two hashes again, their main words were two closer.
This hash and many more hash are one way. This means that a function or hash can be done to a word or phrase, but there is no way to find the word again from that hash. It is not possible to write any such function. Then the low is standing. Let's give an example of a password. Suppose, Dabir's password 'Flood 1988' He inserted it on the bank's website. The website hash has password hash using the hash-52 hash. That hash was kept in database only. Now anyone who has a hashbased password will not know the actual password. It is not possible to write a function that can convert that hash to the inserted password.
When the password will be inserted for logon, then the system hashh will first. That hash will be exactly the same as before, then it will be matched with the hash stored in the database. Hash has to understand that the word is also matched. Then Dabir will be allowed to enter his account. If the database is found, or if the database is hacked, then password will be hidden. It is understood that the common saying comes from here- the snake will die, the sticks will not break.
Flood 1988's hash: 6 C 97031092 E 94 BEF2 B4 FD 77 A 67 AC4 B2 F6 A 6579 F 489 FADAA1 D 59 A 52 DC 97634 EDA
Now if someone receives the above hash and adds a meaningful or meaningless word to the hash function, and if it matches the hash, then match it with the upper hash and when it matches, it will know the password of the debate. The reason is that the word is inserted into the hash function. Again the hash function creates the same hash for one word all the time. It is easy to understand that it is not easy.
Another thing to say is, the Market-tree system is followed in the Block Chain. Holding the hash of another block in a block There is no other block hash in the marginal block. As a result, a particular transaction is written in a block, it is possible to find it very quickly.

3.Proof of Work
Almost all crypto system mining was made harder based on the number of miners. By which the harder it is to do is 'Proof of Work'. It is made harder by putting 'zero' in front of the hash. As much as zero, it is difficult to solve mathematical problems. If two are zero, it's not twice as hard as one, because the difficulty is increasing at the geometric rate. Proof of work ensures that no one computer or company can affect the entire network, and the mining work is not so easy. If there are difficult prices, hacking is reduced or closed. Because, for this difficult task, many need counting power is needed. The proof of work in the bitcoin is placed in such a place that no more than one block is created every 10 minutes. That is why when the number of miners increases, then the job of finding 'nance' from hash is made stronger in the front of a hush.
According to most of the crypto sources, the number of coins is fixed. They are slowly mined out. For example, the total number of Bitcoin has been fixed at 20 million. His time has also been fixed. All Bitcoin will be mined in 2114. That's how the network is created. A block in every ten minutes. If the excavator increases the excavation will be difficult. It is a real mine, where the mine will be extracted, it will be difficult to lift.
After each block of 2016, this protocol will test the proof of work again. If it takes two weeks to block the previous 2016, then the problem remains the same. If it takes less time then it will increase. If it takes more time, the difficulty will be reduced. Keeping the speed of the network protocol can be lifted every ten minutes in such a way. Creating a block in 10 minutes takes approximately two weeks to build 2016 block.