Bitcoin is just part of it. How to create trust without a central authority, principles of decentralization, smart contracts, gas fees, Layer 2 solutions, DAOs, and the Oracle Problem.
A comprehensive deep dive into client-side storage. From Cookies to IndexedDB and the Cache API. We explore security best practices for JWT storage (XSS vs CSRF), performance implications of synchronous APIs, and how to build offline-first applications using Service Workers.
App crashes only in Release mode? It's likely ProGuard/R8. Learn how to debug obfuscated stack traces, use `@Keep` annotations, and analyze `usage.txt`.
Why your server isn't hacked. From 'Packet Filtering' checking ports/IPs to AWS Security Groups. Evolution of Firewalls.
Digitized paper signature. Verify with public key, sign with private key. Unforgeable, non-repudiation. Core tech of blockchain and HTTPS.
When I send $10 to you via a banking app, no physical cash moves.
Instead, the bank updates its database (Ledger): Me -10, You +10.
We rely on the bank as a Trusted Third Party. We trust that the bank won't steal our money or make a mistake.
But what if the bank goes bankrupt? What if the government freezes your account? The 2008 Financial Crisis showed us the fragility of this trust. In response, Satoshi Nakamoto asked a fundamental question: "Can we maintain a shared ledger without a central server?"
This is how Blockchain was born. It is a technology for creating trust in a trustless environment.
To understand why this is revolutionary, we must look at the history of money.
Bitcoin is not just "digital money". It is the first form of money that is scarce like gold, divisible like fiat, portable like email, and trustless like mathematics. It removes the need for kings and bankers to validate our wealth.
Blockchain is essentially a Shared Linked List that everyone has a copy of.
A block is like a page in a ledger book. It contains:
Blocks are chained together using cryptography (Hash Functions like SHA-256). Block 100 contains the hash of Block 99. Block 99 contains the hash of Block 98. This creates a dependency chain all the way back to the Genesis Block (Block 0).
Why is it secure? If a hacker tries to modify a transaction in Block 50:
This property makes blockchain Immutable. Once written, it cannot be erased or altered.
In the digital world, copying is free. If I email you a photo, I still have the photo. But money shouldn't be copied. If I send you 1 BTC, I must lose it. This is the Double Spending Problem.
Traditionally, banks solved this by keeping a central ledger. In Blockchain, Consensus Algorithms solve this.
"The first computer to solve a super-hard math puzzle gets to write the next block and earns Bitcoin."
"The one who locks up (stakes) the most coins gets to write the block."
Bitcoin is "Programmable Money". Ethereum takes it further: "Programmable Computer."
A Smart Contract is code deployed on the blockchain. It executes automatically when conditions are met. No lawyers or middlemen needed.
Smart contracts also enable DAOs (Decentralized Autonomous Organizations). Imagine a company without a CEO. Instead, decisions are made by code and community voting. Users hold Governance Tokens (e.g., UNI, ENS) which represent voting rights. This is a radical experiment in human organization.
Smart contracts live on the blockchain and can't see the outside world (like "Is it raining in London?"). They need a bridge called an Oracle. Chainlink is the most famous example. It brings real-world data (stock prices, weather) into the blockchain securely.
Proposed by Vitalik Buterin, this theory states you can only have 2 out of 3:
Current solution trends point towards Layer 2 (L2) rollups like Arbitrum or Optimism. They process transactions off-chain quickly and only write the final results to Ethereum for security. This is like settling the bar tab at the end of the night instead of paying for every sip.
The first era of the internet copied information. (Web 1.0 & 2.0). The blockchain era moves value. (Web 3.0).
Is it a bubble? Maybe. Is the technology revolutionary? Absolutely. It solves the "Double Spending Problem" without a central authority. For developers, learning Solidity or Rust opens doors to building DApps that belong to no single corporation but to the network itself.
It is a shift from Web 2.0 (Read-Write) to Web 3.0 (Read-Write-Own). This shift empowers users with data sovereignty and financial autonomy, challenging the centralized models of Big Tech and traditional finance.
