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Payjoin: Randomly round the payment output if it is one input tx

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nicolas.dorier
2020-04-13 13:34:23 +09:00
parent b0073af5aa
commit 1d2540543b
2 changed files with 17 additions and 1 deletions
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16
BTCPayServer/Payments/PayJoin/PayJoinEndpointController.cs
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@@ -341,6 +341,22 @@ namespace BTCPayServer.Payments.PayJoin
{
var change = await explorer.GetUnusedAsync(derivationSchemeSettings.AccountDerivation, DerivationFeature.Change);
var randomChangeAmount = RandomUtils.GetUInt64() % (ulong)contributedAmount.Satoshi;
// Randomly round the amount to make the payment output look like a change output
var roundMultiple = (ulong)Math.Pow(10, (ulong)Math.Log10(randomChangeAmount));
while (roundMultiple > 1_000UL)
{
if (RandomUtils.GetUInt32() % 2 == 0)
{
roundMultiple = roundMultiple / 10;
}
else
{
randomChangeAmount = (randomChangeAmount / roundMultiple) * roundMultiple;
break;
}
}
var fakeChange = newTx.Outputs.CreateNewTxOut(randomChangeAmount, change.ScriptPubKey);
if (fakeChange.IsDust(minRelayTxFee))
{