Phase 4 — Privacy Techniques

Bitcoin is transparent by default. Every transaction is permanently recorded on a public ledger. Privacy requires deliberate technique — this phase teaches you how.

"Privacy is not secrecy. A private matter is something one doesn't want the whole world to know, but a secret matter is something one doesn't want anybody to know." — Hal Finney

Weeks 8–12: Reclaiming fungibility

Primary resources

Resource Focus
Bitcoin Fungibility Wiki Privacy concepts and techniques
CoinJoin Developer Guide Collaborative transaction privacy
Wasabi Wallet Docs WabiSabi CoinJoin implementation
Samourai Wallet Mobile privacy wallet
JoinMarket Decentralized CoinJoin market

Platform path: Bitcoin Privacy Techniques

Week 8: Understanding the transparency problem

Key concepts

Concept Explanation
Pseudonymity Addresses are not names, but all activity is public
Chain analysis Linking addresses to identities via heuristics
Fungibility Every unit should be interchangeable — transparency breaks this
UTXO labeling Your wallet knows which coins are "tainted" by history
Common input ownership Heuristic: inputs in same tx belong to same entity

Study questions

  1. Why is Bitcoin pseudonymous but not anonymous?
  2. How do chain analysis companies cluster addresses?
  3. What is the difference between privacy and fungibility?
  4. Why does accepting KYC bitcoin into your wallet reduce your privacy?

Exercise

  1. Look up a known address on mempool.space
  2. Trace its transaction history
  3. Note how quickly you can build a picture of activity
  4. Reflect: this is what chain analysis companies do at scale

Week 9: CoinJoin fundamentals

How CoinJoin works

Before CoinJoin:
  Alice → 1 BTC → Exchange (visible link)

After CoinJoin:
  Alice ─┐
         ├─→ Mixed transaction ─→ Alice' (1 BTC, no link)
  Bob   ─┘                      Bob'   (1 BTC, no link)

Multiple users collaborate to create a transaction where inputs and outputs cannot be linked.

Implementations

Tool Type Notes
Wasabi Wallet Desktop CoinJoin WabiSabi protocol, coordinator-based
Samourai Whirlpool Mobile CoinJoin Stonewall + Ricochet + Whirlpool
JoinMarket Market-based Earn fees as maker or pay as taker
Mercury Wallet Layer-2 statechain Different trust model

Exercise

  1. Read the CoinJoin developer guide
  2. Understand the difference between maker and taker roles
  3. Study one implementation's documentation in depth

Weeks 10–12: Practical privacy workflow

A privacy-conscious Bitcoin workflow

1. Acquire bitcoin (prefer non-KYC sources)
2. Receive to fresh address (never reuse)
3. Run your own node (don't leak to third-party nodes)
4. CoinJoin before consolidating
5. Use separate wallets for separate purposes
6. Route node traffic through Tor
7. Never link on-chain activity to real identity

Advanced techniques

Technique What it does
PayJoin Break input-output clustering heuristics
Lightning Off-chain payments with better privacy
Silent Payments Reusable donation addresses without linkability
Coin control Choose which UTXOs to spend
Stonewall Decoy transactions that look like CoinJoin

Parallel: Monero

For private money beyond Bitcoin's limitations, study the Monero Privacy Path in parallel during weeks 10–12.

Checkpoint — Bitcoin track complete

  • [ ] I understand why Bitcoin is not private by default
  • [ ] I can explain CoinJoin to someone in plain language
  • [ ] I have studied at least one privacy wallet implementation
  • [ ] I run my own node (preferably Tor-only)
  • [ ] I practice address reuse avoidance and coin control
  • [ ] I understand the tradeoffs between Bitcoin privacy tools and Monero

Congratulations. You have completed the Bitcoin learning track from whitepaper to privacy techniques.

Where to go next