diff options
| -rw-r--r-- | bip-0078.mediawiki | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/bip-0078.mediawiki b/bip-0078.mediawiki index 3bb8fc3..d67ab08 100644 --- a/bip-0078.mediawiki +++ b/bip-0078.mediawiki @@ -117,6 +117,7 @@ The payjoin proposal MAY: The payjoin proposal MUST NOT: * Shuffle the order of inputs or outputs, the additional outputs or additional inputs must be inserted at a random index. +* Decrease the absolute fee of the original transaction. ===BIP21 payjoin parameters=== @@ -249,6 +250,7 @@ The receiver needs to do some check on the original PSBT before proceeding: The sender should check the payjoin proposal before signing it to prevent a malicious receiver from stealing money. +* Verify that the absolute fee of the payjoin proposal is equals or higher than the original PSBT. * If the receiver's BIP21 signalled <code>pjos=0</code>, disable payment output substitution. * Verify that the transaction version, and the nLockTime are unchanged. * Check that the sender's inputs' sequence numbers are unchanged. @@ -529,6 +531,10 @@ public async Task<PSBT> RequestPayjoin( if (sequences.Count != 1) throw new PayjoinSenderException("Mixed sequence detected in the proposal"); + decimal newFee = proposal.GetFee(); + decimal additionalFee = newFee - originalFee; + if (additionalFee < 0) + throw new PayjoinSenderException("The receiver decreased absolute fee"); // For each outputs in the proposal: foreach (PSBTOutput proposedPSBTOutput in proposal.Outputs) { @@ -545,8 +551,6 @@ public async Task<PSBT> RequestPayjoin( // The amount that was substracted from the output's value is less or equal to maxadditionalfeecontribution if (actualContribution > optionalParameters.MaxAdditionalFeeContribution) throw new PayjoinSenderException("The actual contribution is more than maxadditionalfeecontribution"); - decimal newFee = proposal.GetFee(); - decimal additionalFee = newFee - originalFee; // Make sure the actual contribution is only paying fee if (actualContribution > additionalFee) throw new PayjoinSenderException("The actual contribution is not only paying fee"); |