Here’s an article on the topic:
Error Message: “Non-Mandatory Script-Verify-Flag (Invalid Schnorr Signature)” When Spending a Taproot Transaction via Musig2
When using the musig2 library at Rust for Taproot Transactions, you may encounter an error message indicating that your schnorr signature is an invalid. This Error Occurs Due to a Misunderstanding or How Musig2 Handles Script Verification Flags.
What is Script Verification?
Script Verification in Bitcoin Allows Developers to Sign Transactions and Scripts Using Digital Signatures. The script-verify flag specifications which type of script the programmer hens to execute when verifying a transaction or script. There are three types of script verification: mandatory, non-mandatory, and optional.
The Issue with Musig2
In the context of Taproot Transactions, Musig2 uses a variant or schnorr signatures. Crimps Allow for Multiple Owners to Participate in a Single Transaction by Aggregating them Into a Single Output. However, when using script-verify flags, musig2’s default glory can lead to an error message indicating that your signature is invalid.
The Error Message
When spending a Taproot Transaction via Musig2 with Two Owners, You May Encounter the Following Error Message:
`
Invalid Script Verification Flag: Non-Mandatory Script-Verify-Flag (Invalid Schnorr Signature)
`
This Error Occurs Because Musig2’s Default Gaavian Requires That All Script Verification Flags Be Non-Mandatory. However, in this case, there are one or more mandatory script verification flags present.
The Solution
To resolve this issue, you need to manuely specific which script verification flag should be used. The Correct Command Line Option is -S 1 (Script Verification Flag 1), Where the Number Corresponds to the Type of Verification Required.
Here’s An Example:
`Rest
Use Musig2 :: Taproot :: TaprootTransaction;
Let MUT TX = TaprootTransaction :: New ();
// Manually specific Script Verification Flags
TX.Sign (& Mut RMP :: RMP :: New (“Script-Verify-0”, “Script-Verify-1”));
TX.Sign (& Mut RMQ :: RMQ :: New (“Script-Verify-2”));
// Spend The Transaction
TX.Spend (& RMP :: RMP :: New (“some_Script”));
`
In This Example, We Manually specific Script-Verify-0 andScript-Verify-1 to Enable Mandatory Script Verification Flags. The Error Message Should Now Be Resolved.
Conclusion
When Using Musig2 for Taproot Transactions, It’s Essential to Understand How Script Verification Flags Work and How to Correctly specific them to Avoid Errors Like the One Described Above. By Manually Specying the Correct Script-Verify Flag, You Can Ensure That Your Transactions Are Signed Successully and Error-Free.