# Introduction to Web 3

## I don't know WTF

PPR: Pricing, Portofolio-mgmt, Risk-mgmt

Trading （金融科技聖杯） is on top of paper, not pepper

## Finance

like "時光機" or "任意門"

跟未來的自己借錢、跟遠在地球另一端的的人借錢

價值：資產、收益（預期標的物收成分潤）、便利性、安全性

## Web 3

- Web 3 is the internet owned by the builders and users, orchestrated with tokens

## Blockchain

### Seed Phrase and Key

- Mnemonic phrase (usually 12 or 24 words)
- Private key ➜ Derive public key ➜ Then derive address (e.g., 0xabc...123)

### Transaction and Signing

- The transaction, before being signed, is typically in a JSON format.
- After signing, it becomes a cryptographic signature, often represented as a hexadecimal string.
- The signed transaction is sent to a node for verification using the sender’s public key.
- The transaction enters the consensus mechanism and is permanently recorded on the blockchain.

## Wallets

### Software Wallet - MetaMask

The private key is encrypted and stored in the browser's local storage.

#### Disadvantages:
- Since the extension can access the private key and is integrated with the browser, there is a risk of leakage.
- The private key can be exposed if tricked by a phishing website and clicking a button.
- It may be vulnerable to malicious scripts being injected.

#### Advantages
- It allows convenient interaction with functions on websites.

### Web Wallet - FTX

The private key is in the company's hands.

#### Disadvantages:
- The company could go bankrupt.
- The company might misuse your funds for gambling.
- The company could be hacked.

#### Advantages:
- Access to various exchange functions like long/short trading, staking, lending, etc.
- No need to interact with underlying calls directly.

### Cold Wallet - Paper / Hardware

The private key is on a piece of paper.

#### Disadvantages:
- Requires knowledge of underlying functionality for interactions.

#### Advantages:
- Secure.

## Smart Contract Implementation

- CLI or GUI
- EOAs or Smart Contract Account

### Ethereum Gas

- 合約運行時會根據使用到的指令和空間消耗對應的 gas
- 總花費 = gas * gas price
- gas price 是浮動的，由 base fee (根據前一個區塊的壅塞程度調整) + priority fee (小費) 組成
- 因為協助驗證區塊的 validator，會根據其質押的 eth 獲得相對應獎勵，為了避免通貨膨脹，gas 中的 base fee 會被銷毀 ( burn )，priority fee 則保留給礦工作為額外收入

**Remix IDE**: https://remix.ethereum.org

## Key Perspectives: Essence & Blockchain’s 5w1h

### Essence: 金融科技區塊鏈本質 (with CS2)
金融科技區塊鏈’s essentials:

#### WHY 金融科技區塊鏈?
Decentralization: PayFi (“指東打東, 指哪打哪”): A peer-to-peer electronic cash system.
#### WHAT is it?
Ledger formed by value-yielding consensus. (If today is a small class, we’ll do a CS2 here too.)
#### HOW to do it?
Proof of work
#### WHO owns this value?
Proof of knowledge
#### WHEN to do it?
Blockchain literally means block chained after block, which is after another block etc.
Block time = ?
#### WHERE is it?
To the users, it’s where the Lightning network is.
Internet companies: User-centric and growth-hacking. vs. some crypto companies’ 90-10 rule.