Bitcoin: Are Segwit-format transactions with all non-witness inputs valid?
Introduction
The introduction of Segwit, an extension to the Bitcoin protocol designed to improve scalability and reduce transaction times, has raised questions among many users about the validity of certain transaction formats. In this article, we will explore whether a Segwit-format transaction with all non-witness program (NWP) inputs is valid.
What are types of non-witness programs?
Non-witness programs in Bitcoin refer to functions or scripts that are not part of a witnessed transaction. They can include user-defined code, such as smart contract execution functions. The goal of Segwit was to improve the performance and efficiency of these types of transactions by reducing the amount of memory required.
What is Segwit?
Segwit is an innovation in the Bitcoin protocol designed to improve scalability and reduce transaction times. This allows for the creation of new transaction types, such as segwit-spend, which can be used to transfer funds without including a full script. It also allows for more efficient execution of smart contract functions.
Validity of Segwit-format transactions
When it comes to valid segwit-format transactions with NWP inputs, we need to consider the following key aspects:
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NWP inputs
: Non-witness program inputs must be in script form. Script types can include various options, such as pay-to-script-priority (P2SP), pay-to-witness-program (P2WP), pay-to-address-priority (P2AP), and pay-to-bitcoin-composite-priority. (P2BCCP).
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Script hashes: The hashing of the script input is very important to determine its validity.
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Script length: The length of the script input must not exceed a certain threshold depending on the specific transaction type.
Example of Segwit Transaction Format
Let’s look at an example of a Segwit transaction format with inputs of non-witness program types:
[nVersion][token][flag][txins][txouts][witness]
Here “txins” is the input transaction index, “txouts” is the output transaction index, and “witness” indicates whether a witness or script hash should be included.
Is this valid?
For this particular example to be valid according to Segwit standards, the following conditions must be met:
– The NWP inputs are in the form of scripts with the specified types (P2SP, P2WP, etc.).
– The hashes of these input scripts match their respective “txins” and “txouts”.
– There is no invalid or excessive script length.
Conclusion
Finally, while certain transaction formats may be valid according to Segwit standards, the above conditions must be met to ensure that the input NWP transactions are indeed correct. This ensures the proper execution of smart contract functions on the Bitcoin network.
Example Use Case
Here is an example use case:
[nVersion][marker][flag][txins][txouts]
In this format, the “n” represents a new version of the protocol. The remaining parameters indicate whether the input NWP transactions should include witness or script hashes.
[1,0][1][0x00000000][01]
This sample transaction with inputs of non-witness program types (P2SP and P2WP) would be valid according to Segwit standards, assuming that the hashes of these scripts match their respective “txins” and “txouts”.
Note
The format shown is a simplified representation, not an actual Bitcoin transaction. In practice, more precise information is included in real transactions.
Conclusion
In this article, we investigated whether segwit-format transactions are valid with all types of non-witness programs. By understanding the requirements for NWP input scripts according to the Segwit standards, users can create valid transactions that meet these specifications.