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The recent introduction of new Payment-to-Anyone (P2A) spending in Bitcoin has sparked curiosity about the nature of these scripts. In particular, we examine whether “scriptSig spending” is expected to always be empty.
Understanding Script Sig Spending
In Bitcoin, “Sig Spending” by a script means that it is responsible for paying a fee to unlock a transaction. The script signature contains information about who or what originally paid the fee, but this does not necessarily mean that there are actual withdrawable funds associated with the script signature.
P2A Spending: A New Era of Simplification
The introduction of P2A spending represents a significant departure from traditional Bitcoin transactions. Unlike regular Public Key Hash (P2PKH) addresses, which require a “scriptPubKey” to unlock the transaction and transfer funds, P2A spending has an optional “scriptSig” component. This new format promises to simplify the process of approving payments.
The problem of script sig outputs
Now that we know the concept of script signature outputs, let’s address the question of whether it can be assumed that they are always empty. The reason is simple: when someone has paid a fee in a P2A transaction, they have not necessarily spent their own money. In other words, there could be multiple wallets involved in the payment process, each contributing to the same P2A output.
This raises an interesting question: is « scriptSig output » always equal to « 0x00000000000000000000000000000000000000000000000000000000000000000000000000000001 » as some might expect? Not necessarily.
The answer
In short, yes, it is possible for “scriptSig spending” to be empty in certain cases. Here’s why:
Multiple wallets can contribute to the same P2A output.
Some transactions may not have a corresponding script signature at all (e.g. when using a special “PayToAnchor” (P2A) address).
The existence of other wallets with scripts that spend different amounts of coins may result in empty “ScriptSig spending” values.
However, it must be noted that the P2A standard for releasing transactions is still based on the concept of script sig spending. When a wallet receives a payment from an external source (e.g. a P2A transaction or a PayToAnchor address), it typically spends its own funds associated with the “scriptSig” component.
In conclusion
While scriptSig spending is not always expected to be empty, there are scenarios where it can happen. To mitigate these risks, Bitcoin developers and users should be aware of the possibility that multiple wallets may contribute to the same P2A output or other wallet-specific script sig values.
Understanding how the new P2A outputs work and the implications of their design can help us better navigate the world of Bitcoin payments and transactions.