{"id":37327,"date":"2020-05-06T07:00:49","date_gmt":"2020-05-06T04:00:49","guid":{"rendered":"https:\/\/forklog.com\/en\/?p=37327"},"modified":"2025-08-29T15:20:21","modified_gmt":"2025-08-29T12:20:21","slug":"what-is-coinjoin-what-is-zerolink-what-is-stonewall","status":"publish","type":"post","link":"https:\/\/forklog.com\/en\/what-is-coinjoin-what-is-zerolink-what-is-stonewall\/","title":{"rendered":"What is CoinJoin? What is ZeroLink? What is STONEWALL?"},"content":{"rendered":"
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1<\/span><\/p>\n

What is CoinJoin?<\/strong><\/p>\n

CoinJoin is a technique for anonymising bitcoin transactions.<\/div>\n<\/div>\n
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2<\/span><\/p>\n

Who created CoinJoin, and when?<\/strong><\/p>\n

The CoinJoin protocol was introduced<\/a> in 2013 by Gregory Maxwell, a Bitcoin Core and Blockstream developer.<\/div>\n<\/div>\n
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3<\/span><\/p>\n

What problem does CoinJoin solve?<\/strong><\/p>\n

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Contrary to a common refrain, bitcoin does not offer full anonymity. Analysis of the public blockchain can link transactions to an individual.<\/p>\n

Bitcoin transactions consist of inputs (sending addresses) and outputs (receiving addresses). When a user wants to transact, they select unspent transaction outputs (UTXOs) as inputs, specify outputs and sign the inputs. Each input is signed independently, and users may specify multiple outputs.<\/p>\n

Example of a transaction with four inputs and two outputs:<\/p>\n

\"\u0427\u0442\u043e<\/p>\n

This transaction has four inputs (0.2 BTC each) and two outputs (0.7 BTC and 0.09 BTC). It is obvious to an observer that a payment is being made: the sender pays one output to someone and returns the change to themselves. Because four inputs were used, the larger output is likely the payment to the recipient. A fee of 0.01 BTC is deducted and collected by the miner.<\/p>\n

An observer might also infer that the sender is consolidating smaller inputs to create a larger UTXO (0.7 BTC).<\/p>\n

Another inference from such a transaction is that each input is signed independently.<\/p>\n

CoinJoin addresses the lack of genuine anonymity in bitcoin.<\/p>\n<\/div>\n<\/div>\n

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4<\/span><\/p>\n

How does CoinJoin work?<\/strong><\/p>\n

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An analogy for CoinJoin is a group pooling their cash in one wallet before going shopping. Everyone can watch that no one overspends, but purchasers do not necessarily use the very banknotes they contributed.<\/p>\n

With CoinJoin, several parties jointly construct a transaction; each provides inputs and desired outputs. Once all inputs are combined, it becomes impossible to say with confidence which output belongs to which user.<\/p>\n

Example:<\/p>\n

\"\u0427\u0442\u043e<\/p>\n

Four participants want to break links between transactions. They coordinate among themselves (or via a dedicated coordinator) and state which inputs and outputs they want included.<\/p>\n

The coordinator embeds this information into a transaction, each participant signs it, and the transaction is broadcast. After participants have signed, it cannot be altered; otherwise it becomes invalid. There is therefore no risk of the coordinator stealing funds.<\/p>\n

The transaction acts as a black box that mixes coins. The old UTXOs are spent and new ones created. The only connection between the old and new UTXOs is the transaction itself, but its participants cannot be identified. At most, one can know that a participant supplied one of the inputs and may be the new owner of a final output.<\/p>\n<\/div>\n<\/div>\n

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5<\/span><\/p>\n

Are there weaknesses in CoinJoin?<\/strong><\/p>\n

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