How does Kaspa's sighash mechanism protect data attached to a transaction payload?

Kaspa's signature hash (sighash) system was updated so that signing a transaction also cryptographically covers any data stored in the payload field. When you send a Kaspa transaction, a sighash is computed — a fingerprint over the transaction's key fields — and your private key signs that fingerprint, not the raw transaction. With payload support enabled, the payload is hashed into a value called payload_hash, which is then folded into the overall sighash. For backwards compatibility, if the payload is empty, the zero hash is used as the payload_hash, so older transaction formats still verify correctly. This matters for beginners because it means payload data cannot be swapped out after signing — any change to the payload invalidates the signature, giving the same tamper-evidence guarantee that already protects transfer amounts.