PrivateSend and InstantSend

PrivateSend

This documentation describes how to use the PrivateSend feature to create CoinJoin transactions with your Dash for consumer grade privacy.

Background

PrivateSend is a trustless (i.e. non-custodial) method of running a sequence of transactions (known as “CoinJoin”) such that an observer has difficulty tracing transaction history. The current implementation of PrivateSend in the Dash Core wallet allows any amount of Dash to be processed. PrivateSend is also available in the Dash Electrum wallet.

Knowledge of the exact number of rounds of PrivateSend has a quantifiable effect on the confidence an adversary may have when attempting to guess transaction history. For this reason, the recommended (and default) number of rounds of PrivateSend is set to four, and some inputs may pass through additional rounds to further improve privacy.

You can read more about PrivateSend theory and processes here.

Configuration

  1. Open your Dash Core wallet, go to Settings and select Options. Go to the PrivateSend tab.

    ../../_images/options-privatesend.png
  2. Next to PrivateSend rounds to use, enter a value between 1-16. Each round of PrivateSend performs one CoinJoin transaction, known as a denomination. Higher numbers of rounds increase your overall level of privacy while decreasing the chance of detection via node collusion. 16 is the highest number of rounds currently available.

    NOTE: To prevent system abuse, an average of one in ten rounds incurs a fee of .0001 DASH.

  3. Enter a Target PrivateSend balance. This value provides a lower boundary on the final amount of funds to be processed. Depending on how the client splits your wallet balance, you may end up with denominated inputs whose sum total is slightly greater than the target amount.

  4. Click OK to save settings.

  5. PrivateSend is disabled by default when you open the wallet. It will only start after you set the number of rounds and number of Dash to process under settings and click Start Mixing on the Overview tab of your wallet.

Starting CoinJoin

The PrivateSend process is initiated by clicking the Start Mixing button on the Overview tab of the Dash Core wallet. CoinJoin is possible once the following conditions have been met:

  • The wallet contains sufficient non-denominated funds to create the minimum required denominated values.

  • The user has not disabled PrivateSend in the Options dialog.

  • The target value for processed funds in the Options dialog is greater than zero.

If your wallet is encrypted (highly recommended), you will be asked to enter your wallet passphrase. Enable the Only for mixing via PrivateSend checkbox to unlock the wallet for CoinJoin only.

../../_images/mixing-password.png

Entering a password for PrivateSend processing only

This will unlock your wallet, and the PrivateSend process will begin. The wallet will remain unlocked until PrivateSend processing is complete, at which point it will be locked automatically.

../../_images/mixing.png

PrivateSend interface after clicking the Start Mixing button. Note the Status is Enabled.

PrivateSend will begin creating transactions and your PrivateSend balance will gradually increase. This process can take some time, so be patient. You can monitor the process in more detail as described in the following section.

Any of the following actions will interrupt the process. Because the transactions are atomic (they either take place completely, or do not take place at all), it is possible to safely interrupt PrivateSend at any time.

  • Clicking the Stop Mixing button on the Overview tab

  • Closing the client before PrivateSend is completed

  • Sending PrivateSend funds from the wallet before PrivateSend rounds are completed

  • Disabling PrivateSend before the process is complete

Monitoring PrivateSend

If you want to monitor PrivateSend in more detail, you need to enable some advanced features of the wallet. Go to Settings, select Options and go to the Wallet tab. Check the Enable advanced PrivateSend interface checkbox. This will allow you to monitor progress and see which individual operations PrivateSend is carrying out in the background.

../../_images/mixing-progress.png

Monitoring PrivateSend progress

Since PrivateSend creates a lot of new address keys to send and receive the denominations, you may receive a warning when the number of remaining keys runs low. This is nothing to be worried about, since the wallet will simply create more keys as necessary. However, these keys will not exist in any previous backups of your wallet. For this reason, it is important to backup your wallet again after the process is complete.

You can also monitor PrivateSend progress by viewing the transactions created by the process on the Transactions tab.

../../_images/privatesend-transactions.png

Transactions created by PrivateSend on the Transactions tab

The following table describes the PrivateSend-related transactions displayed in the Type column of the Transactions tab:

PrivateSend Transaction Type

Transaction Description

PrivateSend Make Collateral Inputs (CoinJoin)

Wallet funds were moved to collateral inputs that will be used to make collateral payments. This is done to minimize traceability of collaterals.

PrivateSend Create Denominations (CoinJoin)

Wallet funds were broken into PrivateSend denominations (Step 1 here)

PrivateSend Denominate (CoinJoin)

A transaction was sent to a masternode in order to participate in a CoinJoin session (Step 3 here)

PrivateSend Collateral Payment (CoinJoin)

The CoinJoin session collateral was claimed. This fee is charged in ~10% of sessions to prevent spam attacks.

PrivateSend (Spending)

Denominated funds were used to send a payment to someone. Note: Unlike the previous 4 transaction types, this is not a CoinJoin transaction.

You can also use the coin control feature to view which addresses hold denominations ready to be used for PrivateSend transactions. Go to the Send tab of your wallet and click Inputs to view the possible input addresses for your transactions. You can see how each address holds given denominations of Dash, and how many rounds have been completed. This is to ensure that an efficient combination of addresses can be used as inputs in PrivateSend transactions without too much change, since an amount in a PrivateSend transaction must be rounded up to completely spend all inputs. The current minimum balance for an input used in a PrivateSend transaction is 0.00100010 DASH.

../../_images/privatesend-addresses.png

Coin Selection dialog showing addresses holding PrivateSend balances in different denominations

Paying with PrivateSend

You can only use PrivateSend for payments once you have processed enough Dash to make up the amount you are trying to send. Because the process takes time, it must be done in advance before you create the send transaction. A PrivateSend transaction is effectively the same as any other transaction on the blockchain, but it draws only from input addresses where the denomination has previously been processed to ensure privacy of funds. Because several input addresses are usually required to make up the amount you are trying to send, a PrivateSend transaction will usually take up more space (in kilobytes) on the blockchain, and therefore will be charged a slightly higher fee.

To send a payment using PrivateSend, go to the PrivateSend tab of the Dash Core wallet. The balance displayed is your PrivateSend balance instead of the total balance as shown on the Send tab. You can then enter the Pay To address, Label, Amount and click PrivateSend. Your payment will be rounded up to completely spend the lowest possible denomination of denominated balance available (currently to the nearest 0.001 DASH). You will be prompted to enter your password and receive a detailed breakdown of the fee structure for PrivateSend before sending.

../../_images/privatesend-send.png

Dash Core ready to send a PrivateSend transaction. Note use of the PrivateSend tab and the amount to be sent is less than the available PrivateSend balance

Inputs

Like all Dash transactions, PrivateSend transactions are composed of a number of inputs and one or more outputs. PrivateSend transactions do not use change addresses, so any remaining Dash will be spent on the transaction fee.

Due to the probabilistic nature of the PrivateSend process, increasing the number of inputs in a transaction may marginally reduce privacy. For this reason, using PrivateSend is not recommended for users requiring a high level of privacy. While it is not possible to link a PrivateSend transaction to a single source address with absolute certainty, using more inputs may make a transaction more vulnerable to different potential linking attacks. There are a number of chain analysis companies that possess tools that can provide transaction risk scoring services for transactions on the Dash blockchain, including PrivateSend transactions.

You can reduce the number of inputs in a PrivateSend transaction by defining the transaction amount in such a way that it consumes your available input denominations more efficiently, or by processing more Dash to ensure enough appropriately denominated inputs are available. Use the Coin Control function in the PrivateSend tab to view and select or deselect CoinJoin UTXOs currently available for use as transaction inputs.

InstantSend

Introduction

This documentation describes how to use InstantSend to instantly send funds to any other Dash user around the world. Since the release of InstantSend based on Long Living Masternode Quorums (LLMQ-IS) in Dash 0.14, the Dash network itself will attempt to generate an InstantSend lock for almost every transaction processed by the network, according to these rules. Unlike the prior implementation of InstantSend, which required a higher fee, LLMQ-IS locks transactions without any action taken by the user. For this reason, only the recipient needs to monitor the network for the transaction lock in order to be able to receive funds and process transactions with immediate settlement.

Dash InstantSend is supported by many wallets and vendors, including (but not limited to) the following:

  • Dash Core Wallet

  • Dash Android Wallet

  • Dash iOS Wallet

  • My Dash Wallet

  • Kraken

  • Bitrefill

  • and many more…

You can read more about InstantSend theory and processes here.

InstantSend Transactions

Since Dash 0.14, all user-facing interface options to create an InstantSend transaction have been removed, because all transactions are effectively InstantSend transactions. As before, the recipient is responsible for monitoring the network for the InstantSend lock and implementing user-facing logic and interfaces to continue with transaction processing after payment has been recieved. See the InstantSend Integration documentation for more information on how to monitor for InstandSend locks.