Web3 Concepts

This repository contains focused, implementation-level explorations of core blockchain and Web3 concepts. The work here prioritises first-principles understanding of how blockchain systems function under the hood, rather than framework-driven application development.

The projects are written in JavaScript using EVM-aligned cryptographic and execution models, with an emphasis on correctness, testability, and clarity.

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Purpose

The goal of this repository is to internalise and demonstrate:

• how cryptographic primitives enable trustless systems
• how transactions are constructed, signed, and verified
• how blocks are formed, validated, and chained
• how tampering and invalid state transitions are detected

This is a conceptual exploration repository, not a production codebase.

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Projects

1. Cryptography

Ethereum cryptography utilities for message hashing, signing, and key recovery.

Features:

• Message hashing using Keccak-256
• Message signing with private keys
• Key recovery from signatures
• Address generation from public keys

Files:

• hashMessage.js - Hash messages using Keccak-256
• signMessage.js - Sign messages with private keys
• recoverKey.js - Recover public keys from signatures
• getAddress.js - Generate Ethereum addresses from public keys
• test.js - Test suite for all utilities

Usage:

cd cryptography
npm install
npm test

2. Find Colours

A utility to find the original color from a hash value. Given a hash, it determines which color (from a predefined set) produced that hash.

Features:

• Hash color values using SHA-256
• Reverse lookup to find the original color from a hash
• Supports colors: red, green, blue, yellow, pink, orange

Files:

• index.js - Main function to find colors from hashes
• test.js - Test suite for color finding functionality

Usage:

cd find_colours
npm install
npm test

3. Miner

A simple blockchain miner implementation that demonstrates proof-of-work mining. It creates blocks by finding a nonce that produces a hash below a target difficulty.

Features:

• Transaction mempool management
• Proof-of-work mining with configurable difficulty
• Block creation with nonce finding
• Processes up to 10 transactions per block
• SHA-256 hashing for block validation

Files:

• index.js - Mining logic with mempool and block management
• test.js - Test suite for mining functionality

Usage:

cd miner
npm install
npm test

4. Blockchain

A simple blockchain implementation demonstrating the core concepts of blockchain technology, including block creation, chain validation, and tampering detection.

Features:

• Block creation with data and previous hash linking
• Blockchain validation to ensure chain integrity
• SHA-256 hashing for block verification
• Detection of tampering with previous hashes or data
• Genesis block initialization

Files:

• Block.js - Block class with data and hash functionality
• Blockchain.js - Blockchain class with chain management and validation
• validationTests.js - Test suite for blockchain validation

Usage:

cd blockchain
npm install
npm test

5. UTXO

A UTXO (Unspent Transaction Output) model implementation demonstrating how Bitcoin-style transactions work. This simple JS project shows how transactions consume input UTXOs and create new output UTXOs, with validation and fee calculation.

Features:

• Transaction Output (TXO) representation with owner, amount, and spent status
• Transaction execution with input and output UTXO validation
• Prevention of double-spending by checking if UTXOs are already spent
• Automatic fee calculation as the difference between input and output amounts
• Support for multiple input and output UTXOs per transaction

Files:

• TXO.js - Transaction Output class representing unspent outputs
• Transaction.js - Transaction class for executing UTXO-based transfers
• test.js - Test suite for transaction execution and fee calculation

Usage:

cd utxo
npm install
npm test

6. Binary Search Tree

A binary search tree implementation demonstrating fundamental tree data structure concepts. This project shows how nodes are organized in a hierarchical structure with efficient insertion and search operations.

Features:

• Node class with data, left, and right child references
• Recursive node insertion maintaining binary search tree property
• Recursive search functionality to find nodes by value
• Tree structure with root node management
• Efficient O(log n) average case for insertion and search operations

Files:

• Node.js - Node class representing tree nodes with data and child references
• Tree.js - Tree class with recursive addNode and hasNode methods
• test.js - Test suite for tree operations and node insertion

Usage:

cd binary-search-tree
npm install
npm test

7. Simple Merkle Tree

A Merkle tree implementation demonstrating how cryptographic hash trees work. This project shows how multiple data items are combined into a single root hash through recursive pairing and concatenation, a fundamental concept in blockchain data structures.

Features:

• Recursive tree construction by pairing and concatenating nodes
• Flexible concatenation function for different hashing strategies
• Root hash generation from any number of leaves
• Merkle proof generation for leaf verification
• Merkle proof verification to validate proofs against root
• Handles base cases including single leaf and empty tree scenarios
• Automatic handling of odd-numbered nodes in layers (unpaired nodes are passed through)
• Efficient hierarchical hashing structure with recursive layer building

Files:

• index.js - MerkleTree class with recursive layer building, root generation, and proof generation
• verify.js - Proof verification function to validate merkle proofs against root
• testUtil.js - Utility functions for SHA-256 hashing, hash concatenation, and proof verification
• test.js - Comprehensive test suite with 32 tests covering root generation (1-8 leaves), proof generation (10 leaves), and proof verification (11 untampered + 4 tampered scenarios)

Usage:

cd simple-merkle-tree
npm install
npm test

Technologies

• Node.js - Runtime environment
• ethereum-cryptography - Cryptographic utilities for Ethereum
• crypto-js - Cryptographic library for hashing
• Mocha - Testing framework
• Chai - Assertion library

Installation

Each project has its own dependencies. Navigate to the project directory and run:

npm install

Testing

Run tests for each project:

npm test

License

ISC

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These projects are part of my learning journey with Alchemy.