Spend proof

Spend authorization and payment evidence

The wallet has separate get_spend_proof and check_spend_proof interfaces. The proof binds the transaction and supplied message to a demonstration involving the secret information for its inputs.

Payment verification checks the destination and amount of an output. A transaction key or payment proof addresses that question through a different interface. Choose the proof that answers the recipient's question.

References: Monero source: wallet/wallet2.cpp · Wallet RPC reference

Historical data is part of verification

PR #11696 reports that a malicious daemon can substitute inputs in historical version-1 transaction data when the requested hash has not been independently established. Its proposed correction retrieves the full legacy transaction and verifies the hash before using those inputs.

The PR remained open on 9 November 2026, and the pinned stable release does not include its correction. The issue concerns proof verification against untrusted historical data, not a demonstrated way to extract a wallet seed or spend its funds.

References: Monero PR #11696: legacy spend-proof verification

Example

Alice needs to show that she created a transaction. She supplies a spend proof for its transaction ID and an agreed message. Bob verifies those inputs rather than treating the proof as evidence of a payment to his own address.

References: Monero source: wallet/wallet2.cpp · Monero PR #11696: legacy spend-proof verification

Limits and cautions

A spend proof does not by itself prove the recipient, paid amount or a person's legal identity. Verification also depends on obtaining the correct transaction data. Legacy version-1 verification has a proposed correction still under review.

References: Monero source: wallet/wallet2.cpp · Monero PR #11696: legacy spend-proof verification