Blockchain From Scratch

Ongoing Project – Building a minimal UTXO-based blockchain from the ground up to gain a deep, hands-on understanding of how Bitcoin-style systems work.

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🚀 Project Overview

This repository is an evolving learning lab. Each day, new features go in to explore core blockchain concepts:

• UTXO Model – Track unspent transaction outputs and build a reliable ledger.
• Mempool – Collect, validate, and prioritize pending transactions before mining.
• Signing & Verification – Use public/private key cryptography to sign transactions and guarantee authenticity.
• Miner Fees – Enforce fee markets so miners are rewarded fairly and users compete for block space.
• Proof-of-Work Mining – Implement a hash-puzzle mechanism to secure the chain and regulate issuance.
• Block & Chain Validation – Verify every block’s proof-of-work, transaction integrity, and consensus rules.
• Fork Handling & Longest-Chain Rule – Track side-branches, reorganize on heavier work, and converge on a single history.

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📦 Features (In Progress)

• Transaction Lifecycle

  • Create, serialize, and hash transactions.
  • Sign with ECDSA; verify signatures on every node.
  • Enforce correct input→output sums + fee extraction.

• Mempool Management

  • In-memory pool indexed by TX ID, fee-rate priority queue, and UTXO locks.
  • Reject double-spends and low-fee spam.
  • Emit transactionAdded events for miners and UIs.

• Mining & Rewards

  • Assemble candidate blocks from top-fee TXs + coinbase reward.
  • Adjustable difficulty & target suppression via leading-zero hashes.
  • Add total fees to miner’s reward output.

• Chain Storage & Traversal

  • Store blocks in a hash map; compute max-height tip on every addition.
  • Unfold parent pointers to extract the canonical “longest chain.”
  • Handle orphans and side forks until one branch wins.

• Utilities & Tools

  • CLI scripts to bootstrap a test network of nodes and wallets.
  • Automated tests: unit suites for UTXOPool, Transaction, Block, and integration flows (wallet → mempool → miner → chain).
  • Sample fixtures for default transactions and wallets.

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⚙️ Getting Started

1. Clone the repo

   git clone https://github.com/your-username/blockchain-from-scratch.git
   cd blockchain-from-scratch

2. Install dependencies

   npm install

3. Run tests

   npm test

Building blockchains one line of code at a time.