Blockchain Technology – Module 1 Quick Review

Distributed Systems & Blockchain

• Distributed system = many nodes acting as one logical platform.
• Node types: honest, faulty, malicious (Byzantine).
• Byzantine Generals Problem → need for Byzantine Fault Tolerance (BFT).
• PBFT (1999, Castro–Liskov): practical consensus despite Byzantine failures.
• Key challenges: fault tolerance, network partitioning.

CAP Theorem

• Impossible to achieve all three simultaneously:
  1. Consistency (C)
  2. Availability (A)
  3. Partition Tolerance (P)
• Public chains: favor $A+P$ (eventual consistency).
• Private chains: favor $C+P$ (lower availability).
• Consortium chains: favor $C+A$ (weak partition tolerance).

Timeline (Key Milestones)

• $1982$ – David Chaum: mutual-suspicion ledger concept.
• $1991$ – Haber & Stornetta: timestamped docs.
• $1992$ – Add Merkle trees.
• $2008$ – Satoshi Nakamoto: Bitcoin white-paper.
• $2009$ – First Bitcoin software.
• $2014$ – “Blockchain” term popularized.

Blockchain Basics

• Decentralized, distributed, append-only ledger.
• Removes intermediaries via P2P network + consensus.

Core Components / Generic Elements

• Blocks: data + timestamp + prev-hash + own hash.
• Distributed ledger on P2P network.
• Cryptographic hashing (e.g., SHA-256).
• Consensus algorithms: PoW, PoS, PBFT, etc.
• Smart contracts (programmable logic).
• Node roles: full, miner/validator, light.
• Incentives/tokenomics (public chains).

Key Features

1. Decentralization (no single authority).
2. Transparency (public auditability).
3. Immutability (tamper-proof data).
4. Security (cryptography).
5. Consensus without central trust.
6. P2P networking (fault tolerance).
7. Smart contracts & programmability.
8. Tokenization & incentives.
9. Privacy (pseudonymity, ZK options).

Consensus Mechanisms (Essentials)

• Proof of Work (PoW): secure, energy-heavy, $\approx 10$ min/block.
• Proof of Stake (PoS): stake-based, energy-light.
• Delegated PoS (DPoS): token-holder voting, high TPS.
• Practical BFT (PBFT): message agreement, permissioned use.
• Proof of Authority (PoA): trusted validators, enterprise focus.

Blockchain Generations (Tiers)

1. 1.0 – Cryptocurrency payments (Bitcoin). Issues: scalability, energy.
2. 2.0 – Smart contracts & DApps (Ethereum). Issues: congestion, security bugs.
3. 3.0 – Scalability, interoperability, privacy (Polkadot, Solana).
4. 4.0 – Enterprise & AI/IoT integration (Hyperledger Fabric, Corda).

Major Applications

• Cryptocurrencies & DeFi.
• Supply chain traceability.
• Healthcare EHR.
• Voting & e-governance.
• Identity/KYC, IoT, cybersecurity.
• NFTs, gaming, metaverse, carbon credits, etc.

Benefits vs. Limitations

Benefits:

• Decentralization & trustless interaction.
• Transparency/immutability (audit trails).
• Enhanced security.
• Cost & time reduction (smart contracts).
• Improved data integrity.

Limitations:

• Scalability: Bitcoin $\approx 7\,\text{TPS}$ vs Visa $65\,000\,\text{TPS}$.
• High energy (PoW).
• Regulatory uncertainty.
• Privacy & permanent data exposure.
• Storage bloat; smart-contract vulnerabilities.
• Complex cross-chain security.