Overview

This repo represents the implementation of a basic blockchain from scratch, and entirely in C, as part of the Holberton Training Program.

Topics

• What is a Blockchain?
• 0x00. Blockchain - Crypto
• 0x01. Blockchain - Data structures concepts
• 0x02. Blockchain - Block mining

What is a Blockchain?

A blockchain is essentially a digital ledger of transactions that is duplicated and distributed across the entire network of computer systems on the blockchain, each block contains data and a reference to the previous one in the list. Visit this blog to learn more about it.

0x00. Blockchain - Crypto

Tasks

"0. SHA256" :Function that computes the hash of a sequence of bytes

"1. EC_KEY creation" : Function that creates a new EC key pair

"2. EC_KEY to public key": Function that extracts the public key from an EC_KEY opaque structure

"3. EC_KEY from public key": function that creates an EC_KEY structure given a public key

"4. EC_KEY - Save to file": function that saves an existing EC key pair on the disk.

"5. EC_KEY - Load from file": function that loads an EC key pair from the disk

"6. Signature": Implementing a function that signs a given set of bytes, using a given EC_KEY private key

"7. Signature verification": Implementing a function that verifies the signature of a given set of bytes, using a given EC_KEY public key

8. Library: Creation of a Makefile that compiles all the previous functions and archives them into a static library for future use.

0x01. Blockchain - Data structures concepts

Tasks

"0. Create Blockchain":Write a function that creates a Blockchain structure, and initializes it

"1. Create Block":Write a function that creates a Block structure and initializes it.

"2. Delete Block": Write a function that deletes an existing Block

"3. Delete Blockchain": Write a function that deletes an existing Blockchain, along with all the Blocks it contains/li>

"4. Hash Block": Write a function that computes the hash of a Block

"5. Save Blockchain": Write a function that serializes a Blockchain into a file

"6. Load Blockchain": Write a function that deserializes a Blockchain from a file

"7. Block validity": Write a function that verifies that a Block is valid

0x02. Blockchain - Block mining

Tasks

"0. Proof of work": Write a function that checks whether a given hash matches a given difficulty

"1. Block is valid v0.2": check if a Block’s hash matches its difficulty

"2. Block mining": Write a function that mines a Block in order to insert it in the Blockchain

"3. Adjust difficulty": Write a function that computes the difficulty to assign to a potential next Block in the Blockchain.

Requirements

• Ubuntu 14.04 LTS
• OpenSSL library
• Vagrant
• VirtualBox
• C programs that will be compiled with gcc and some APIs to create and manipulate linked-lists.

References

• https://help.ubuntu.com/community/OpenSSL#Practical_OpenSSL_Usage
• https://medium.com/@hassini.abir/what-is-a-blockchain-and-why-it-is-so-secure-53a6d565798c