Before we start digging into Tezos itself, let's review the basics of blockchain and cryptocurrencies. This module will present a brief history of the blockchain, its main components, consensus mechanisms, and the use cases of blockchain.

Introduction

A blockchain is a decentralized ledger of all transactions across a peer-to-peer network. Using this technology, participants can confirm transactions without a need for a central clearing authority. The blockchain is an immutable - (unchangeable, meaning a transaction or file recorded cannot be changed) distributed digital ledger (digital record of transactions or data stored in multiple places on a computer network) with many use cases beyond cryptocurrencies.

History of Blockchain Technology: A Detailed Guide

Structure of Blockchain

Blockchains are decentralized records. Instead of being stored in one central location, the blockchain is stored on the computers of every user of that given blockchain. Blockchains are made up of blocks that are linked to each other by a hash which is unique for every block.

The first block in a blockchain is called the genesis block.

A block contains:

• A batch of valid transactions
• Hash of the block - It is a hexadecimal number and is always unique. It connects all the blocks in a blockchain. If the data changes in a block, the hash also changes.
• Hash of the previous block - Every block stores the hash of its previous block.

<aside> 💡 Learn more about the basic working of blockchain here

</aside>

How do Blockchains Work?

The chaining of blocks by their hashes, as described above, makes blockchain immutable. As the block is derived from the information contained in the previous block in the blockchain, tampering with a block will make all the blocks after it invalid. But, nowadays computers are fast enough to recalculate hashes of all the blocks and to make blockchain valid again. Therefore hashing itself is not enough to prevent tampering.

In order to make blockchain more secure, it is distributed over a network, which means valid blocks have to be replicated on all network nodes. Everyone connected to the network has a full record and copy of the blockchain. When a new block is created, it is sent to everyone to verify if it is tampered with. All nodes create a consensus and validate a block. If the block validates then it is added to all the nodes.