In the case of a Stonewall transaction, the wallet will build the transaction using multiple inputs and four outputs, only one is the spend and the other three are all sent back to the sender’s wallet with one of them being the same size as the spend. Both Samourai Wallet and Sparrow Wallet will attempt to compose a Stonewall transaction by default when spending.
You can review this transaction on your favorite Bitcoin testnet explorer, for example on mempool.space .
The transaction has four outputs and two of them are the same size, one 42,000 sat spend and one 42,000 sat decoy. To an external observer they can not tell which outputs belong to the entity in control of any of the inputs. Three out of the four outputs are being returned to the sender’s post-mix wallet.
Sparrow Wallet
To make a Stonewall spend with Sparrow Wallet:
Enter the address that you wish to spend to.
Add a label.
Enter the amount to spend.
Set the miner fee rate.
Notice the difference in how the transaction is constructed when selecting the “Efficiency” setting; there are two outputs, the spend and the change:
Contrast that with selecting the “Privacy” setting; this builds a Stonewall transaction where there are four outputs including a decoy spend:
Click on “Create Transaction.”
Then on the next screen, click on “Finalize Transaction for Signing.”
If everything looks good on the next screen, select “Sign.”
Once signed, you can broadcast the transaction.
You can review this transaction on your favorite Bitcoin testnet explorer, for example on mempool.space .
mempool_stonewall.png
The transaction has four outputs and two of them are the same size, one 690,000 sat spend and one 690,000 sat decoy. To an external observer they can not tell which outputs belong to the entity in control of any of the inputs.
Post-Mix Spending Tools: Ricochet
Ricochet is a post-mix spending tool that creates multiple hops between the initial sending transaction and the final destination. This technique can be useful when sending bitcoin to a destination where the receiver will snoop back through your transaction history to determine if there is something about your UTXO they don’t like.
Oftentimes this type of behavior is carried out by exchanges or some merchants; read this article by 6102 for more details on CoinJoin flagging. There is no industry standard that these flagging companies adhere to, they will arbitrarily decide how many hops back is within their own risk tolerance. But the five hops that Ricochet provides seems to be doing the job. Sparrow Wallet does not support Ricochet transactions. Samourai Wallet collects a 100,000 sat fee for this service.
To compose a Ricochet transaction in Samourai Wallet:
Navigate to your post-mix wallet and press the blue “+” sign.
Then select “Send.”
Toggle on the “Ricochet” option.
Then toggle on the “Staggered delivery” option if you want each hop to be in a separate block.
Otherwise, all five hops will occur in the same block, which may be preferable to you if time is of the essence.
Then paste or scan the address you would like to spend to.
Enter the amount to spend (the amount you want deposited to the final destination).
Then press “REVIEW TRANSACTION.”
Set the miner fee rate (the miner fee for all five hops is figured in).
Review the transaction details.
If everything looks good, press “SEND” and then confirm the spend to broadcast the transaction to the network.
Here is how this Ricochet transaction looks on testnet. You can follow the hops along the way.
Conclusion
This article explained how the wallet structure works in the Whirlpool-enabled wallets, Samourai Wallet and Sparrow Wallet .
By understanding the anonymity benefits achieved through Whirlpool, you can then better understand which post-mix spending tool is right for the job. Each post-mix spending tool was explained in detail with step-by-step instructions on how to use them and the additional anonymity preservation benefits they offer.
To learn more, join the communities on the Samourai Wallet Telegram channel or the Sparrow Wallet Telegram channel , where you will find several other users helping each other out on a variety of topics.
This is a guest post by Econoalchemist. Opinions expressed are entirely their own and do not necessarily reflect those of BTC Inc or Bitcoin Magazine.
