Clear DefinitionsCoinJoin
1 min read
Pronunciation
[koyn joyn]
Analogy
Like pooling different people’s cash in a hat and redistributing it; observers cannot tell which original bill went to which person.
Definition
A privacy technique where multiple users combine their transactions into a single joint transaction, obfuscating the link between inputs and outputs.
Key Points Intro
CoinJoin enhances transaction privacy by mixing UTXOs among participants.
Key Points
Input anonymity: Breaks input-output linkage.
Coordinator: Optional party assembles joint transaction.
Fees: Participants share small mixing fees.
Script types: Works with standard P2PKH, P2WPKH UTXOs.
Example
Technical Deep Dive
Protocol: Participants register inputs with coordinator, receive blinded output addresses, coordinator constructs transaction, participants sign. Chaumian variant uses blind ECDSA to prevent coordinator from linking outputs. Security relies on at least two honest participants.
Security Warning
Coordinator can deanonymize if blind signatures are flawed. Use non‑custodial, open‑source implementations and avoid low‑participant rounds.
Caveat
Mixing reduces but does not eliminate traceability; chain analysis techniques continue to evolve.
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