![](https://steemitimages.com/DQmNjgvMPdnkMvNN3xJcb6yGcgBbzTJ62dZFQebjFKMXrso/image.png) ## A hunter’s guide to one of the most influential technologies on earth >“Any sufficiently advanced technology is indistinguishable from magic “— Arthur C. Clarke # What is a Blockchain? ![](https://steemitimages.com/DQmZHysG2TEwFKxWuH8XqtUEddZuJ29qoA4wc4FhW2uiAne/image.png) Essentially, we can say, the Blockchain is a way we store information using cryptographic functions, linked data structure, and certain governance protocols in a decentralized manner. Basically, that’s it. But let’s break down this simple definition using the keywords visible. ## Cryptographic Functions The blockchain uses cryptography to create hashes for data units on the blockchain. Hashes are unique long complex numbers. They are usually represented as hexadecimal generated from cryptographic algorithms. They work in a sense that when you put A in F(A). It returns X. If you do it for an infinite number of times, F(A) will still return X. Unless you change the contents of A and call it Aa. Then, when used the modified data inside F(Aa) produces a different result, for example, Y. With this, we can identify a particular piece of data as original and the other as fake. An example of such cryptographic function is the SHA-256 hash. ## Linked Data Structure Hashed information on the blockchain is stored in a linked manner. Such that each data block relies on the previous data block to create a new hash identity. Except the first data block called the genesis block. This is what we call a chain. Imagine hashed data organized in blocks. And linked together to produce a single axis called the blockchain. By this way, we realize a hereditary pattern. Because the hash identifier of a previous block added to the created block generates the hash identifier of the next data block. Hence we can witness the parent-child relationship between blocks. ## Decentralized Manner One important feature of the blockchain is how data decentralizes among the nodes. It means each node in the network has a copy of the blockchain and that enhances the security of the blockchain. Data syncs among the nodes and if for some reason, one node goes rogue, it is easy to identify and actions are taken. The more the nodes, the more secure the blockchain. ## Let’s build one ! Now that we have a fair idea of what the blockchain is, why don’t we build our own blockchain solution for business use. I will use python to build. The source code can be found here. Note this part requires you to have basic programming concepts to grasp. ## Case Our business firm stores critical business documents that are vital to our clients. They cannot be tampered with. We want to take advantage of the security and distributed nature of a blockchain. This will keep our documents secure and away from loss and tampering. So we are building a new way of storing our documents on the blockchain. Which will make our storage immutable, distributed and practically uncrackable. ## Design Our blockchain is for private and business use. So it should be permission based. This means one has to be registered on the network to be able to add documents to the blockchain. Also, since we are building j small-scale solution and an experimental one. I will use very simple protocols to govern how the blockchain validates data added. I will use a protocol I came up with called the Block Limit Protocol to validate blocks. Block Limit Protocol maintains that documents in a single block should be less than 5 and shouldn’t be empty. Else the system will reject the block. Since it is permission-based, only registered users can create and submit new docs signed in their name. ## The Code ``` from hashlib import sha256 from time import time import json class Blockchain: def __init__(self, authors, name="blockchain"): """ Creates a blockchain with genesis block :param authors: a list of registered users :param name: name of the blockchain,default is 'blockchain' :return: