Mixer and CoinJoin Output: Recording Contamination Without Overstating It

Mixers and CoinJoin protocols deliberately break the link between source and destination addresses. Funds that pass through them carry a documentation footprint that a counterparty review will recognise, and the file records that footprint accurately rather than smoothing over it.

A mixer pools funds from many users and pays out to fresh addresses controlled by the same users. From the outside the input and output cannot be matched with certainty, only with probability that depends on the protocol, the pool size, and the timing of each entry.

CoinJoin is a non-custodial variant. Multiple users sign a single transaction that mixes their inputs and outputs without an intermediary holding the funds. The on-chain entry is visible, but the linkage between any specific input and any specific output is intentionally obscured.

The documentation file records the entry into the mixer and the exit address that the client claims as theirs. The claim is supported, where possible, by signed-message evidence from the exit address or by contemporaneous wallet logs that show the receipt at the expected time.

Probability of linkage is described rather than asserted. Where heuristics indicate the exit address with a stated confidence, the confidence level and the heuristic used are recorded so that a reviewer can weigh the claim against the documented methodology rather than against silence.

Counterparty posture matters. Some counterparties decline to receive funds that have any mixer exposure, regardless of evidence. The engagement records this as a factor for the client to weigh, but does not advise the client on which counterparties to approach with the file.

Where contamination cannot be resolved, the file says so. A counterparty reviewer is more likely to accept a file that discloses an open question with documented analysis than a file that obscures the analysis to present a cleaner appearance than the chain data supports.

Our role is to structure on-chain evidence into a documentation file. We do not advise the client on the legality of any prior transaction, do not represent the client to any exchange, and do not produce evidence for criminal or civil proceedings arising from the analysis.