1.1 Definition and Origin of Blockchain

Learning Objective: Understand the fundamental definition of blockchain, its historical roots, and its close connection with Bitcoin.

Definition:

Blockchain is an advanced digital ledger technology that organizes and stores data in units called “blocks” and links these blocks sequentially using cryptographic principles to form a “chain”. This chain creates a distributed, transparent (in public blockchains), and tamper-resistant shared database maintained across multiple computer nodes. Each block records a set of transactions within a specific timeframe and includes a timestamp, ensuring chronological order and traceability.

Origin:

The concept of blockchain technology can be traced back to 1991, when Stuart Haber and W. Scott Stornetta proposed a system to address the issue of digital document timestamping. However, blockchain gained widespread attention and real-world application in 2008, when a mysterious individual or group under the pseudonym “Satoshi Nakamoto” published the groundbreaking whitepaper “Bitcoin: A Peer-to-Peer Electronic Cash System”. Bitcoin became the world’s first successful cryptocurrency and the first killer application of blockchain technology, aiming to enable secure and trusted value exchange without the need for centralized institutions.

1.2 How Blockchain Works

Learning Objective: Gain a deep understanding of how blocks are created and verified, how chains are formed to ensure data integrity, and the vital role of miners (or validators) in achieving network consensus.

The working of blockchain can be summarized as a cyclical process of “Transaction Packaging into Blocks → Blocks Linked into a Chain → Network Consensus Assurance”.

Workflow:

1. Transaction Creation and Broadcasting:
   When a user initiates a transaction (e.g., transferring digital assets or executing a smart contract), the transaction is signed and broadcast to the entire blockchain network.
2. Transaction Verification and Block Creation:
   Specific nodes in the network (known as “miners” in Proof of Work (PoW) or “validators” in Proof of Stake (PoS)) collect these pending transactions. They verify the legitimacy of transactions (e.g., checking the sender’s balance and signature validity), then package a batch of verified transactions into a new “block”. Each new block contains a unique identifier (hash) of the previous block, creating an unbreakable chain.
3. Chain Formation and Immutability:
   Once the new block is confirmed through the consensus mechanism, it is added to the existing blockchain. Since each block references the hash of its predecessor, any attempt to modify historical blocks would result in a cascading change to all subsequent blocks, making tampering computationally infeasible and easily detectable. This design ensures data integrity and immutability.
4. Consensus Mechanism and Record-Keeping Rights:
   To ensure all participants in the network agree on the blockchain’s state, a consensus mechanism is employed. For example, in Bitcoin’s PoW, miners must solve a complex mathematical puzzle using significant computational resources to win the right to create a new block (“record-keeping rights”) and earn block rewards (newly minted coins and transaction fees). Other consensus mechanisms, such as Proof of Stake (PoS) and Delegated Proof of Stake (DPoS), operate differently but share the goal of ensuring fair, secure, and efficient network operations.

1.3 Core Characteristics of Blockchain

Learning Objective: Comprehend the key features of blockchain, including decentralization, transparency, immutability, security, and pseudonymity.

Key Features:

1. Decentralization:
   Data is not stored on a single centralized server but is maintained and stored across thousands of nodes in the network. This distributed architecture eliminates single points of failure and significantly reduces the control of centralized entities.
2. 透明性:
   In public blockchains, all transaction records (usually pseudonymous, not linked to real identities) are publicly accessible. Anyone can query and verify the transaction history via blockchain explorers, ensuring operational transparency.
3. Immutability:
   Once data is written to the blockchain and confirmed by a majority of nodes, it becomes almost impossible to unilaterally alter or delete it. This is ensured by cryptographic hash links and consensus mechanisms, providing a high level of trustworthiness.
4. セキュリティ:
   By combining cryptography (e.g., digital signatures and hash algorithms), decentralized architecture, and consensus mechanisms, blockchain effectively resists various attacks (e.g., data tampering and double-spending), offering robust security.
5. Pseudonymity:
   Users on the blockchain are represented by cryptographic addresses (derived from public keys) rather than their real-world identities. While transaction data is public, mapping blockchain addresses to real-world identities requires additional information, providing a degree of privacy.
6. Consensus-Driven:
   All changes (e.g., adding new blocks) on the blockchain must be confirmed through the consensus mechanism, ensuring data consistency and orderly system operation.

1.4 Blockchain Architecture and Types

Learning Objective: Understand the common layered architecture of blockchain technology and distinguish between public, private, and consortium blockchains.

Technical Architecture (General Model):

1. Data Layer:
   The foundation of the blockchain, responsible for storing raw data, including transaction details, account balances, digital signatures, timestamps, and hash pointers linking blocks.
2. Network Layer (P2P Layer):
   Constructs the peer-to-peer communication network. It handles data propagation across nodes, such as transaction broadcasting, block synchronization, and node discovery.
3. Consensus Layer:
   Defines the rules and algorithms for achieving network-wide agreement on the blockchain’s state (e.g., PoW, PoS). This layer ensures fair and secure record-keeping and transaction validation.
4. Incentive Layer:
   Primarily present in public blockchains, this layer designs economic models (e.g., block rewards and transaction fees) to incentivize miners/validators to participate honestly in maintaining the network.
5. Contract Layer:
   Allows for the deployment and execution of smart contracts, which are pre-written code that automatically enforces contract terms. This expands blockchain’s functionality beyond just being a ledger.
6. Application Layer:
   The interface between blockchain technology and end-users, encompassing decentralized applications (DApps) and solutions such as wallets, decentralized finance (DeFi), and supply chain systems.

Blockchain Types:

1. Public Blockchain:
   Fully open; anyone can join, read data, send transactions, and participate in consensus (e.g., Bitcoin, Ethereum). It offers the highest decentralization and transparency.
2. Private Blockchain:
   Access is restricted and controlled by a single organization. Node participation, data access, and consensus rights are centrally managed. Suitable for internal enterprise use cases.
3. Consortium Blockchain:
   A hybrid between public and private blockchains, managed by a group of pre-selected organizations. It balances efficiency, privacy, and partial decentralization, ideal for collaborative scenarios like industry consortia.

1.5 Evolution of Blockchain: From 1.0 to 3.0

Learning Objective: Trace the developmental stages of blockchain technology and understand the core breakthroughs and representative applications of each stage.

Blockchain 1.0: Programmable Money

• Era: Digital currency.
• Led by Bitcoin, focusing on decentralized peer-to-peer electronic cash systems.
• Solved double-spending and created a secure, global, censorship-resistant currency system.
  

Blockchain 2.0: Programmable Finance

• Era: Smart contracts and financial innovation.
• Led by Ethereum, introducing smart contracts to automate complex operations.
• Enabled decentralized applications (DApps), DeFi, ICOs, NFTs, and DAOs.

Blockchain 3.0 Programmable Society

• Era: Broad applications beyond finance.
• Focuses on integrating blockchain into supply chains, healthcare, digital identity, IoT, voting systems, and more.
• Emphasizes convergence with AI, big data, and cloud computing to solve societal trust issues and enable efficient collaboration.

1.6 Applications and Future Trends

Learning Objective: Explore blockchain’s potential use cases, analyze its advantages and challenges, and foresee its future direction.

Applications:

1. Finance: Cross-border payments, trade finance, digital identity verification, securities issuance, and insurance automation.
2. Supply Chain: End-to-end product traceability, counterfeit prevention, and inventory optimization.
3. Healthcare: Secure storage and sharing of electronic health records, drug traceability, and clinical trial data management.
4. 不動産: Simplified property registration, asset tokenization, and reduced transaction costs.
5. Voting: Secure, transparent, and verifiable electronic voting systems.
6. Copyright Protection: Immutable ownership records for digital content (e.g., via NFTs).
7. Energy: Peer-to-peer energy trading and efficient energy distribution.

Challenges:

• Scalability issues (e.g., low TPS on Bitcoin/Ethereum).
• High energy consumption (especially in PoW systems).
• Regulatory uncertainty and compliance risks.
• Lack of standardization and interoperability.
• Complex user experience (UX).
• Privacy concerns in open networks.

Trends:

1. Layer 2 Solutions: Rollups, sidechains, and channels to improve scalability.
2. 相互運用性: Cross-chain solutions to connect isolated blockchains.
3. Integration with AI, IoT, and Big Data.
4. Enterprise Blockchain: Adoption of private/consortium solutions for business efficiency.
5. Decentralized Identity (DID): Empowering users to control digital identities.
6. Web3 and Metaverse: Blockchain as the backbone for immersive virtual worlds and the next-generation internet.