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Whirlpool

Whirlpool is a CoinJoin implementation originally developed by Samourai Wallet. It uses a 5-party model with fixed denominations to create privacy on the Bitcoin blockchain.

Other CoinJoin Implementations

Whirlpool is one of several CoinJoin implementations. Others include JoinMarket (decentralized, maker-taker model) and Wasabi Wallet (WabiSabi protocol, 50-150 participants). Each has different trade-offs in terms of privacy, convenience, and censorship resistance.

What Is Whirlpool?

Whirlpool is a CoinJoin protocol where exactly 5 participants come together to mix their bitcoin. Each participant contributes one input of a specific denomination and receives one output of the same denomination.

How It Works

5 users each contribute 0.1 BTC. The coordinator combines all 5 inputs and creates 5 outputs of 0.1 BTC each. An outside observer cannot tell which input funded which output.

Whirlpool Denominations

Whirlpool uses fixed denominations to make the CoinJoin outputs indistinguishable from each other:

Denomination Sats Use Case
0.0005 BTC 50,000 Small amounts, testing
0.001 BTC 100,000 Small payments
0.01 BTC 1,000,000 Medium amounts
0.05 BTC 5,000,000 Larger amounts
0.5 BTC 50,000,000 Large holdings

Fixed Denominations Matter

The fixed denominations are what make Whirlpool effective. If outputs were different sizes, they could be linked to specific inputs.

How Whirlpool Works

Whirlpool wallets use 4 distinct accounts to support the coinjoin process:

Account Index Purpose
Deposit 0' Where you receive unmixed bitcoin
Premix 2147483645' UTXOs waiting to enter a round
Postmix 2147483646' Mixed UTXOs after completing rounds
Bad Bank 2147483644' Doxxic change from Tx0 transactions

When you initiate a mix, your wallet creates a Tx0 transaction. This transaction takes your deposit UTXO(s) and splits them into equal-sized premix outputs. Any leftover bitcoin becomes doxxic change.

Your premix UTXOs enter the queue. When 5 participants are ready, the CoinJoin round executes.

Once the round completes, you receive post-mix outputs of the same denomination. These UTXOs have been mixed with 4 other participants.

Post-mix UTXOs can automatically enter additional rounds (remixes) to increase your anonymity set. Each remix costs no additional service or mining fees.

Whirlpool Fees

Whirlpool charges a coordinator fee for each Tx0. Remixes cost nothing extra - no additional service or mining fees.

Denomination Fee
0.0005 BTC 0.000005 BTC (1%)
0.001 BTC 0.00001 BTC (1%)
0.01 BTC 0.0001 BTC (1%)
0.05 BTC 0.0005 BTC (1%)
0.5 BTC 0.005 BTC (1%)

Spending the Doxxic Change

Remember: Whirlpool's model equalizes coins in the Tx0 before entering pools, which makes tracking harder. This is the most effective coinjoin model, but it has a drawback: a change output that does not go through the coinjoin process, we call this doxxic change.

This change output is created for each Tx0. It is isolated in a specific account named Doxxic Change or Bad Bank depending on the software to avoid using it with your other UTXOs. This point is critical: these UTXOs have not been mixed - their traceability links remain intact and can compromise your privacy by tying you to your coinjoin activity. Handle them carefully and never use them with other UTXOs, mixed or not. Combining a toxic UTXO with a mixed UTXO destroys all privacy gains from coinjoins.

Currently, Ashigaru does not provide direct access to the Doxxic Change account, at least it wasn't found at the time of writing. This feature will likely be added in a future update. In the meantime, the only way to retrieve these funds is to import your seed into Sparrow Wallet. Sparrow usually auto-detects a Whirlpool wallet and gives access to all four accounts, including Doxxic Change. You can then spend those UTXOs like regular bitcoin from Sparrow.

Here are several possible strategies to handle coinjoin change UTXOs without compromising your privacy:

  • Mix Them in Smaller Pools

    If a toxic UTXO is large enough for a smaller pool, this is often the best option. Do not merge multiple toxic UTXOs to reach the threshold - that would link your entries.

  • Mark Them as Unspendable

    Another cautious approach is to keep them in their separate account and not touch them to avoid accidental spending. If BTC appreciates, new pools may become available for their size.

  • Donate Them

    You can donate toxic UTXOs to Bitcoin developers, open-source projects, or nonprofits that accept BTC. This disposes of them usefully while supporting the ecosystem.

  • Buy Gift Cards or Prepaid Cards

    Platforms like Bitrefill allow exchanging bitcoin for gift cards or reloadable Visa cards. This can be a simple, discreet way to spend toxic UTXOs. But be aware that these UTXOs are still linked to their previous history so be careful which ones you spend.

  • Swap Them for Monero

    Samourai Wallet previously offered atomic BTC/XMR swaps, now discontinued. This service exists in Eigen Wallet. You can isolate these UTXOs, convert to XMR, then back to BTC if desired. This method can be costly and depends on available liquidity. Also consider whether you want to potentially risk a UTXO that may be associated with you being given to a third party who can do whatever they want with it.

  • Open a Lightning Channel

    Transferring toxic UTXOs to LN to benefit from lower transaction fees can be useful. However, this may leak information depending on your LN usage, so proceed carefully.

Handle Doxxic Change Carefully

Carefully consider what you want to do with your doxxic change, always proceed carefully.

How to Manage Postmix

After several coinjoin cycles, the best strategy is to keep UTXOs in the Postmix account, letting them remix indefinitely until you actually need to spend them.

Some users prefer moving mixed BTC to a hardware wallet. This is possible, but it requires discipline to avoid compromising privacy gains from coinjoins.

The most common mistake is merging UTXOs. Never combine mixed UTXOs with unmixed UTXOs in the same transaction, or you risk creating links via the CIOH. This means rigorous UTXO management is key - clear and precise labeling is essential. In general, UTXO merging is risky and often leads to privacy loss when done poorly.

Be careful with consolidation of mixed UTXOs with each other, too. Limited consolidation may be acceptable if UTXOs have large anonsets, but it inevitably reduces your privacy. Avoid large or rushed consolidations before sufficient remixes, as they can create deducible links between your coins before and after mixing. When in doubt, do not consolidate postmix UTXOs. Instead, transfer them one by one to your hardware wallet, generating a fresh receiving address each time. Label every transferred UTXO carefully.

It is strongly discouraged to move postmix UTXOs into wallets using minority script types. For example, if you participated in Whirlpool from a multisig P2WSH wallet, few users share that script type. Sending postmix UTXOs back to the same script greatly reduces your anonymity set. Beyond script type, other wallet fingerprints can harm your privacy. The safest option is to spend from the Ashigaru app.

Finally, as with any Bitcoin usage, never reuse a receiving address. Each payment should go to a fresh, unused address.

The simplest and safest method remains: keep mixed UTXOs resting in Postmix, let them remix naturally, and spend only when needed from Ashigaru.

Ashigaru and Sparrow include additional protections against common chain analysis pitfalls, helping you preserve transaction privacy.

Postmix Best Practices

Avoid merging mixed and unmixed UTXOs; prefer spending from Postmix directly; don't reuse addresses; and be cautious with script types and consolidations.

Whirlpool Best Practices

  • Do Multiple Rounds

    One round gives you 5 possible interpretations. Multiple rounds multiply your anonymity set.

  • Wait Between Rounds

    Do not do all your rounds in quick succession. Wait hours or days between rounds.

  • Never Spend Post-Mix Together

    Each post-mix output should be spent independently. Never combine them.

  • Use Tor

    Always route Whirlpool through Tor. Samourai Wallet supports this natively.

  • Label Your Outputs

    Keep track of which UTXOs are post-mix. Never mix them with premix.

  • Use Sparrow for Desktop

    Sparrow Wallet has built-in Whirlpool support for desktop users.

Whirlpool and Ashigaru

Ashigaru is now the primary wallet for Whirlpool. It provides all the features originally offered by Samourai Wallet:

  • Premix wallet: Where you hold bitcoin before mixing
  • Post-mix wallet: Where you receive mixed bitcoin
  • Bad Bank: A pool of post-mix UTXOs that have been through many rounds
  • Stowaway: PayJoin support for spending post-mix bitcoin
  • Ricochet: Adds transactional distance between post-mix and final destination

Ashigaru continues to be actively maintained by an anonymous team committed to Bitcoin privacy and user sovereignty.

Whirlpool Is Now Done via Ashigaru

Ashigaru is a Bitcoin wallet that continues the Samourai Wallet project in a new form. In April 2024, the founders of Samourai Wallet were arrested by American authorities and their servers were seized. While the original Samourai app remained usable, it is no longer maintained.

Ashigaru is a free, open-source fork maintained by an anonymous team to preserve Samourai's functionality and original philosophy: defending the privacy and sovereignty of Bitcoin users. All Whirlpool CoinJoin features are now accessed through Ashigaru.

Excellent guides on using Ashigaru Whirlpool from Loïc Morel can be found on planb academy.

Common Whirlpool Mistakes

This is the single most damaging mistake. It completely destroys the mixing.

One round gives limited privacy. Do at least 3-5 rounds for meaningful privacy.

Without Tor, your IP is exposed to the coordinator and other participants.

Do not mix KYC bitcoin with non-KYC bitcoin in Whirlpool. Keep them separate.

Combining multiple post-mix UTXOs in a single transaction reduces your anonymity set and creates links between your mixed coins.