Транзакция Bitcoin

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The Bitcoin Story
Bitcoin was introduced in 2009 by someone or a group of people known as Satoshi Nakamoto. It aimed to solve the problem faced by fiat currencies with the help of Blockchain technology. As of 2018, there were more than 1,600 cryptocurrencies that followed the concepts of Bitcoin and Blockchain, including, Ethereum, Litecoin, Dash, and Ripple.

Whenever a sender has made a transaction, he sends Bitcoins to a receiver by submitting the transaction on a public Blockchain network of Bitcoin. The miners around the world do verifications to authenticate users. There are specific participants in the Bitcoin network who are identified as miners, and they verify the authenticity of the sender and the receiver. They also validate whether the sender has enough Bitcoins to send to the receiver and also ensure that the sanity of the underlying Blockchain network to the Bitcoin is not corrupt.

Once the miner has authenticated the transaction and verified all the parameters, the transaction is added to a block, and then that block is made part of the main Blockchain. After this is done, transactions that were associated with the block are executed. Once the transaction is complete, the block is added, and the ledgers across all the nodes are updated, thereby allowing all the participants to have the same copy of the information.

Features of Blockchain
These are the four features of Blockchain which we are going to talk about in detail:

We have a public distributed ledger, which works using a hashing encryption.
Every block has a hash value, which is the digital signature of the block.
All the transactions are approved and verified on the Blockchain network using a proof-of-work consensus algorithm.
The Blockchain network utilizes the resources of the miners, who are there to validate the transactions for rewards.
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Public Distributed Ledger
A public distributed ledger is a collection of digital data that is shared, synchronized, and replicated around the world, across multiple sites, countries, and institutions. Now let's consider a blockchain that can be accessed by anyone in the network around the world. If someone tries to alter data in one of the blocks, everyone in the network can see the alteration, because everyone in the network has a copy of the ledger. In this way, data tampering is prevented.

Public Distributed Ledger

Hash Encryption
Blockchain uses cryptography (see definition of "cryptography" above) to ensure that all the data in the blocks is kept secure from unauthorized access and is not altered. Blockchain uses SHA-256 for encryption. SHA-256 is one of the strongest hash functions available. This cryptographic hash algorithm generates an almost unique 256-bit signature for a text. Blockchain also uses digital signatures to validate users.

Each user has a public and private key. The public key is used to identify the user uniquely, and the private key gives the user access to everything in the account. In the process from the sender's side, the sender's message is passed through a hash function; then, the output is passed through a signature algorithm with the user's private key, then the user's digital signature is obtained. In the transmission, the user's message, digital signature, and public key are transmitted.

Hash Encryption

In the process on the receiver's side, the message is passed through a cryptographic function to get a hash value. That hash value is compared with the hash output obtained bypassing the digital signature and public key through a verification function.



As mentioned, each block in a blockchain uses SHA-256 to encrypt and therefore secure the data. Every block has four fields:

Previous hash—this field stores the hash of the previous block in the Blockchain
Transaction details—this field contains information regarding several transactions
Nonce—this field contains a random value (the nonce value) whose sole purpose is to act as a variate for the hash value
Hash address—this field contains the unique identification of the block; it is a hex value of 64 characters, both letters, and numbers, obtained by using the SHA-256 algorithm
The first three values (previous hash, transaction details, and nonce) are passed through a hashing function to produce the fourth value, the hash address of that particular block.