5.1 The Internet and its uses

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Blockchain and Digital Currency

1. What is Blockchain?

A Blockchain is a digital, decentralized ledger that records transactions across many computers. Once a piece of data is recorded, it cannot be changed without altering all subsequent blocks.

The "Shared Diary" Analogy

Imagine a classroom where every student has an identical diary. When the teacher gives a sticker to a student, everyone writes it down at the same time.

  • If one student tries to secretly erase a page or change a name, their diary won't match the other 29 diaries.
  • The class compares diaries regularly. If one doesn't match, it is rejected.
  • This creates Trust without needing a Principal (Central Authority) to watch over them.
Block 1
Data + Hash
➔
Block 2
Link to B1
➔
Block 3
Link to B2

2. Digital Currency (Cryptocurrency)

Digital currency is a medium of exchange that exists only in electronic form. It uses blockchain technology to track who owns what.

Examples: Bitcoin (BTC), Ethereum (ETH), Litecoin (LTC).

How it works in Finance:

  1. Transaction: Someone requests a transfer of currency.
  2. P2P Network: The request is broadcast to a global network of computers (Nodes).
  3. Validation: The nodes verify the transaction using algorithms.
  4. The Block: Once verified, the transaction is combined with others to create a new block of data for the ledger.
  5. Completion: The block is added to the existing chain, and the money is "moved."

3. Advantages & Limitations

Advantages

  • Security: Nearly impossible to hack due to decentralization.
  • Transparency: Every transaction is visible on the public ledger.
  • No Middleman: No need for banks, which reduces transaction fees.
  • Global: Can be sent anywhere in the world instantly.

Limitations

  • Volatility: Prices can crash or skyrocket in minutes.
  • Environment: "Mining" (verifying blocks) uses massive amounts of electricity.
  • Irreversible: If you lose your "Private Key" (password) or send money to the wrong address, it is gone forever.
  • Crime: Anonymity can attract illegal activities.

4. Beyond Money: Uses of Blockchain

Blockchain isn't just for currency. Because it is a "permanent record," it can be used for:

  • Smart Contracts: Agreements that execute automatically when conditions are met.
  • Voting Systems: Ensuring votes cannot be tampered with.
  • Supply Chain: Tracking exactly where a product (like organic coffee) came from.
⚠️ Exam Note: When asked why blockchain is secure, emphasize that it is "Distributed" (stored in many places) and "Immutable" (cannot be changed once written).
End of Blockchain Notes • Ready for Cybersecurity (Malware, Phishing, Cookies)?