Learn cryptocurrency fundamentals (blockchain basics)

Overview

Blockchain is the foundational technology behind cryptocurrencies—a distributed, immutable ledger that records transactions across a network of computers withouteding a central authority. Understanding blockchain is essential for evaluating cryptocurrencies as investment assets.

Core Concepts

[!intuition] Why Blockchain Exists

Traditional finance requires trusted intermediaries (banks, clearinghouses) to prevent double-spending and maintain transaction records. But what if we could create a system where:

• Everyone has a copy of the transaction history
• Mathematical proof replaces trust institutions
• No single entity can alter past records

This is blockchain's core innovation: distributed consensus without central authority.

[!definition] What is a Blockchain?

A blockchain is a chain of blocks, where each block contains:

1. Transaction data (who sent what to whom)
2. Timestamp (when this block was created)
3. Cryptographic hash of the previous block (linking blocks together)
4. Nonce (a number used in mining/validation)

The "chain" property means altering any historical block would require recalculating all subsequent blocks—computationally infeasible in well-designed systems.

Key Properties:

• Immutability: Past records cannot be changed without network consensus
• Transparency: All transactions are visible to network participants
• Decentralization: No single point of control or failure

[!formula] How Cryptographic Hashing Links Blocks

Each block contains the hash of the previous block, creating an unbreakable chain.

Hash Function Properties:

• Deterministic: Same input → same output
• One-way: Cannot reverse hash to find input
• Avalanche effect: Tiny input change → completely different hash
• Collision-resistant: Practically impossible to find two inputs with same hash

$\text{Block}_n = \{\text{Data}_n, \text{Timestamp}_n, \text{Hash}(\text{Block}_{n-1}), \text{Nonce}_n\}$

$\text{Hash}(\text{Block}_n) = \text{SHA-256}(\text{Data}_n \,|\, \text{Timestamp}_n \,||\, \text{Hash}(\text{Block}_{n-1}) \,||\, \text{Nonce}_n)$

Why this step? By including the previous block's hash, any tampering with Block5 would change Block 5's hash, which would invalidate Block 6's reference, then Block 7's, and so on. An attacker would need to recalculate the entire chain faster than honest nodes add new blocks—the basis of blockchain security.

[!example] Example 1: Building a Simple Blockchain

Let's trace three transactions through blocks:

Block 0(Genesis Block):

• Data: "Initial block"
• Previous Hash: 000000... (no previous block)
• Hash: a1b2c3d4...

Block 1:

• Data: "Alice sends 5 BTC to Bob"
• Previous Hash: a1b2c3d4...
• Combined input: "Alice sends 5 BTC to Bob" + "a1b2c3d4..."
• Hash: e5f6g7h8...

Block 2:

• Data: "Bob sends 2 BTC to Charlie"
• Previous Hash: e5f6g7h8...
• Hash: i9j0k1l2...

What happens if someone tries to alter Block 1?

1. Change "Alice sends 5 BTC" to "Alice sends 50 BTC"
2. Block 1's hash changes from e5f6g7h8... to something like x9y8z7w6...
3. Block 2's "Previous Hash" field still says e5f6g7h8...—mismatch detected!
4. The network rejects this altered chain because it's invalid

Why this step matters: The chain structure makes tampering visible and provable. Every node can independently verify integrity.

[!example] Example 2: Consensus Mechanisms (Proof of Work)

How does the network agree on which transactions are valid when there's no central authority?

Proof of Work (PoW) example (Bitcoin):

1. Transaction Pool: Miners collect pending transactions

2. Block Construction: Miner bundles transactions into a candidate block

3. Mining Challenge: Find a nonce such that: $\text{Hash}(\text{Block Data} \,||\, \text{Nonce}) < \text{Target Value}$ For example, find a hash starting with five zeros: 00000a3f2b...

4. Why this step? Finding nonce requires trillions of guesses (brute force). It's computationally expensive, making it costly to create fake transaction histories.

5. Broadcast: Miner broadcasts the solved block to the network

6. Verification: Other nodes verify (takes milliseconds) and add the block to their chain

7. Reward: Miner receives newly created cryptocurrency + transaction fees

The51% Attack Threshold: To alter history, an attacker needs more computing power than the rest of the network combined to re-mine all blocks faster than honest miners extend the real chain.

Time estimates:

• Average 10 minutes per Bitcoin block
• Mining difficulty adjusts every 2,016 blocks (~2 weeks) to maintain this rate

[!example] Example 3: Transaction Verification

Alice wants to send 3 BTC to Bob. Here's what happens:

Step 1: Digital Signature

• Alice has a private key (secret) and public key (known to all)
• She creates: $\text{Signature} = \text{Sign}(\text{Transaction Data}, \text{Private Key}_{\text{Alice}})$

Why this step? Only Alice can create this signature, proving she authorized the transaction.

Step 2: Network Broadcast

• Transaction includes: {From: Alice's public key, To: Bob's public key, Amount: 3 BTC, Signature}

Step 3: Node Verification

• Nodes verify: $\text{Verify}(\text{Transaction Data}, \text{Signature}, \text{Public Key}_{\text{Alice}}) = \text{True}$
• Nodes check Alice has≥3 BTC by tracing her transaction history in the blockchain

Step 4: Mining & Confirmation

• Transaction enters a miner's block
• After mining, transaction is "1 confirmation" deep
• After 6 blocks built on top, it's "6 confirmations" deep (standard for finality)

Why 6 confirmations? Probability of reversal drops exponentially: $(0.1)^6 \approx 0.001\%$ assuming attacker has 10% of network hash power.

[!mistake] Common Misconceptions

Mistake 1: "Blockchain = Bitcoin"

Why it feels right: Bitcoin was the first major application, and the terms are often used interchangeably in media.

The fix: Blockchain is the technology; Bitcoin is one application of it. Other uses include:

• Ethereum: Smart contracts (programmable agreements)
• Supply chain tracking: Walmart uses blockchain for food provenance
• Non-cryptocurrency: Central bank digital currencies (CBDCs)

Think: "Blockchain is to Bitcoin as the internet is to email."

Mistake 2: "Transactions are anonymous"

Why it feels right: No names are attached—just cryptographic addresses like 1A1zP1eP5Q...

The fix: Blockchain is pseudonymous, not anonymous. All transactions are permanently public. If your identity is ever linked to an address (through an exchange KYC, IP address, spending patterns), your entire transaction history becomes traceable.

Real-world impact: Law enforcement has traced ransomware payments and darknet market transactions through blockchain analysis.

Mistake 3: "More decentralization always = better"

Why it feels right: Decentralization is blockchain's main advantage over traditional systems.

The fix: Decentralization involves tradeoffs:

When to choose decentralization: When censorship-resistance and trustlessness are worth the costs (e.g., international remittances avoiding capital controls, Store of value in unstable economies).

When not to: High-frequency trading, micropayments, or applications where trusted parties already exist efficiently.

Deep Dive: The Trilemma

[!formula] Blockchain Trilemma

No blockchain can simultaneously maximize all three:

1. Decentralization: Many independent nodes
2. Security: Resistant to attacks
3. Scalability: High transaction throughput

$\text{Optimization} = f(\text{Decentralization}, \text{Security}, \text{Scalability})$

Subject to: Cannot maximize all three simultaneously

Why?

Proof sketch:

• High decentralization → More nodes must reach consensus → Slower (low scalability)
• High security inPoW → Expensive mining → Fewer can afford hardware → Lower decentralization
• High scalability → Fewer validators or larger blocks → Centralization pressure or weaker security

Examples:

• Bitcoin: High security + decentralization, Low scalability (7 TPS)
• Binance Smart Chain: High scalability (300+ TPS), Lower decentralization (21 validators)
• Layer 2 solutions (Lightning Network): Attempt to solve trilemma by moving some transactions off-chain

[!example] Example 4: Calculating Block Propagation Time

Why can't Bitcoin just make blocks every second instead of 10 minutes?

Parameters:

• Average block size: 1.5 MB
• Network bandwidth: 10 Mbps (typical node in 2020s)
• Number of peer connections: 8

Propagation time: $t_{\text{propagate}} = \frac{\text{Block Size}}{\text{Bandwidth}} \times \text{Number of hops}$

$t_{\text{propagate}} = \frac{1.5 \times 8\text{ Mb}}{10 \text{ Mbps}} \times 3 \text{ hops} \approx 3.6 \text{ seconds}$

Why this matters: If blocks came every 3 seconds, and propagation takes 3.6 seconds, different parts of the network would be mining on different "tips" of the blockchain. This causes frequent orphaned blocks (wasted work) and reduced security.

The rule of thumb: Block time should be ≥10× propagation time to keep orphan rate <1%.

$\text{Block Time} \geq 10 \times t_{\text{propagate}}$

Bitcoin's 10-minute blocks ensure network-wide consensus despite global latency.

Investment Implications

[!intuition] Why Blockchain Properties Matter for Investors

1. Scarcity is Programmable

• Bitcoin's 21 million coin cap is enforced by code, not central bank policy
• Unlike fiat currency, supply inflation is predetermined and transparent

2. Settlement Finality

• After 6 confirmations (~1 hour for Bitcoin), reversal probability is astronomically low
• Contrast with credit card chargebacks (possible for120 days)

3. 24/7 Markets

• No "market hours"—blockchain never sleeps
• Implications: Need for different risk management strategies

4. Custody Risk

• "Not your keys, not your coins"—if exchange holds your crypto, you have counterparty risk (see Mt. Gox, FTX colapses)
• Self-custody requires technical knowledge and security practices

5. Regulatory Uncertainty

• Decentralized nature makes regulation difficult
• Governments may ban, tax differently, or require KYC—price impacts

[!formula] Valuation Challenge: Network Effects

Traditional assets have cash flows to discount. Cryptocurrencies derive value from network effects:

$V \propto n^2 \quad \text{(Metcalfe's Law)}$

Where $V$ = network value, $n$ = number of active users.

Why squared? Each user can transact with every other user: $\text{Possible connections} = \frac{n(n-1)}{2} \approx \frac{n^2}{2}$

Investment approach:

1. On-chain metrics: Active addresses, transaction volume, hash rate
2. Relative valuation: NVT ratio (Network Value to Transactions) similar to P/E ratio
3. Stock-to-flow models: Treat supply schedule like commodity scarcity

Critical caveat: These models have mixed track records. Crypto remains highly speculative.

[!recall]- Explain to a 12-Year-Old

Imagine you and your friends pass around a notebook where you write down who owes what to whom. "Sarah gave John $5 for lunch." "John gave Maria$3 for movie ticket."

Now, what if:

1. Everyone has a copy of the notebook (not just one person who could cheat)
2. Before writing a new page, you must solve a really hard math puzzle (so no one can fake old pages easily)
3. Each new page has a "fingerprint" of the previous page, so if someone tries to erase "Sarah gave John $5" and write "$50" instead, everyone's fingerprints stop matching and we all know someone cheated

That's blockchain! It's a shared notebook (ledger) where:

• Everyone can see all the transactions (transparent)
• No one person controls it (decentralized)
• Cheating is super obvious because the "fingerprints" (hashes) won't match
• You need to solve puzzles to add pages, which costs electricity and time, making it expensive to attack

Bitcoin and other cryptocurrencies use this notebook to send digital money without neding a bank to keep track for us.

[!mnemonic] Remember: CHIPS

• Chained: Blocks linked by cryptographic hashes
• Hashed: One-way functions secure each block
• Immutable: Past records can't be changed without detection
• Public: All transactions visible (but pseudonymous)
• Secure: Requires majority computing power to attack (51%+)

Connections

Prerequisites

• Understand currency pairs and exchange rates - Foundation for crypto trading pairs
• Introduction to commodity markets - Similarities in treating crypto as digital commodity

Related Topics

• Bitcoin vs altcoins - key differences - Specific cryptocurrencies built on blockchain
• Crypto wallet types and security - Practical storage of blockchain assets
• Smart contracts and DeFi basics - Advanced blockchain applications

Advanced Applications

• Layer 2 scaling solutions - Lightning Network, Polygon, etc.
• Consensus mechanisms comparison - PoW vs PoS vs DPoS
• On-chain analysis for trading decisions - Using blockchain data for investment

Flashcards

What is a blockchain? :: A distributed, immutable ledger where transactions are recorded in blocks, each cryptographically linked to the previous block, maintained across a network of computers without central authority.

Concept Map

Hinglish (regional understanding)