• Md Sameer Alam
• Jayant Saksham
• Mridul Bagoria

A blockchain is a decentralised peer to peer computer network which is used as a public distributed ledger [1], and To add a new block to the blockchain, it adheres to the consensus algorithm protocol and also to validate new upcoming transaction blocks [2]. Once a block is inserted in the blockchain it is unalterable, but its forks are possible. Blockchains are considered secure by their design and it also possesses high byzantine fault tolerance. Everytime a new block is added in the blockchain, the chain goes on increasing, the technique which is used to make the blockchain more secure is called cryptography. Every block of the blockchain possesses some properties i.e its cryptographic hash, hash of the previous block, timestamp, and the transaction data which contains the information about the sender, the receiver and the amount of money which is used. Hash is the unique identification of every block by which they are identified and are different from other blocks. Previous hash of the block is very important so that if someone ever wants to corrupt any block then its next block will know that its previous hash is changed and someone is trying to corrupt it, so it prevents the blockchain from any discrepancies. Timestamp is the time when the block is added to the blockchain. Blockchain Transactions are irreversible because we cannot alter any block’s data by keeping the blockchain intact. First blockchain ever was created by a person named Satoshi Nakamoto in 2008. The implementation of blockchain was made possible using bitcoin. This first blockchain made it possible to decentralise the currency and made it the first ever digital currency of the time which took power from the centralised authorities like banks or central servers. A very important concept is there in blockchain which is called double spending. Blockchain ensures that each and every transaction happens only once and the double spending problem never occurs. It is not that easy to insert a block inside the blockchain, it consumes a lot of power to do that because we have to solve a complex mathematical problem which is said to be the proof of work, and as it takes a lot of time and energy, anyone who do it after doing tons of hard work gets a reward which is called mining rewards( example: bitcoin, ether etc) and the process of adding a block into a blockchain is called mining.

Cryptocurrency, Blockchain, Bitcoin, Wallets, Decentralised Currency, Minin

" Blockchain Implementation Using Python", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.10, Issue 5, page no.d387-d394, May-2023, Available :http://www.jetir.org/papers/JETIR2305354.pdf

" Blockchain Implementation Using Python", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.10, Issue 5, page no. ppd387-d394, May-2023, Available at : http://www.jetir.org/papers/JETIR2305354.pdf