claude-dev-suite CoinJoin
A CoinJoin combines inputs from multiple users into a single tx with multiple equal-amount outputs to defeat the common-input- ownership heuristic that chain analysts use.
Heuristic broken
Pre-CoinJoin: chain analysts assume "all inputs of a tx belong to the same wallet". This is true for most txs.
CoinJoin breaks this: 10 users, each contributing 1 input, 10 outputs of equal size. Analyst can't link any specific input to any specific output.
Major implementations
Wabisabi (Wasabi Wallet 2.0)
- Coordinator-mediated with credential-based blinding.
- Users register inputs with the coordinator privately (blind sig).
- Anonymity within the round; coordinator can't link inputs to outputs.
- Wasabi 2.0 uses WabiSabi protocol — successor to ZeroLink.
- Default round: ~50 participants; output amounts in tiered denominations.
Whirlpool (Samourai Wallet, RIP)
- Coordinator-mediated but Samourai shut down 2024 (legal action).
- Used 5x equal-output structure.
- Still technically possible but ecosystem is gone.
JoinMarket
- Maker/taker model:
- Makers offer liquidity passively, earn small fees.
- Takers initiate CoinJoins, pay makers.
- No central coordinator — IRC + onion services.
- Slower / smaller anonymity sets but censorship-resistant.
Privacy properties
After CoinJoin, the linked inputs:
- Have equal anonymity-set among the participants.
- Subsequent tx that mixes them can re-cluster (if you spend two CoinJoined outputs together, observer infers same wallet).
Crucial: maintain post-CoinJoin hygiene:
- Don't combine CoinJoined outputs with non-CoinJoined ones.
- Don't reuse addresses.
- Don't immediately spend (timing analysis).
CoinJoin types
Equal-output ZeroLink/Wabisabi
All outputs are equal (or tiered by denomination). Best privacy.
Variable-output PayJoin (BIP78)
Different mechanism — see payjoin/SKILL.md.
Use cases
- Privacy-conscious users wanting on-chain anonymity.
- Pre-emptive privacy before storing or spending large amounts.
- Pre-spend mixing for high-profile addresses.
Costs
- Per-round fee to coordinator: small percentage of input.
- On-chain tx fee: shared among participants.
- Time: multiple rounds for full anonymity (hours typical).
Status (late 2025)
- Wasabi Wallet 2.0 (zkSNACKs): operational; some legal pressure.
- Whirlpool: Samourai shutdown. Some forks attempting to revive.
- JoinMarket: niche but operational.
- Joinstr (Nostr-based CoinJoin coordination): experimental.
Limitations
- Coordinator availability: Wasabi requires coordinator.
- Anonymity set size: small rounds = weak privacy.
- Post-mix hygiene required; users often re-link unintentionally.
- Exchange refusals: some exchanges (esp. KYC-heavy) refuse deposits from CoinJoin outputs.