I can provide you with an article on how to determine which type of SIGHASH (Sign Hash Algorithm) to append to a truncated transaction at the time of input script verification.

Understanding Bitcoin Transactions and Input Scripts

In Bitcoin, transactions consist of multiple inputs that must be verified before they can be output. Each input has a unique index called a “sighash” or sign hash, which is used to verify the associated private signature key. The sighash determines the type of operation (e.g. verify signature, sign, or send) required for each input.

The Truncated Transaction

A truncated transaction is the first 2-byte segment of a complete Bitcoin transaction packet that contains only the data required for input script verification. It typically includes the version, number of inputs, and other metadata.

Determine SIGHASH Types

To determine which sighash type needs to be appended to a trimmed transaction at the time of input script verification, we need to analyze the sighash values ​​of the trimmed transaction. Here are some steps you need to follow:

• Check first 2 bytes

  : The first two bytes of the trimmed transaction (version and number of inputs) contain a unique identifier for the transaction type.

• Compare with known sighash values: Compare the first two bytes of the trimmed transaction with known sighash values ​​for different input script verification types (e.g. verify signature, sign or send).

• Identify required SIGHASH: Based on the comparison, identify which sighash type is required for input script verification.

Example code

Here is an example of a Python function that takes a trimmed transaction as input and returns the identified sighash type:

on def identify_sighash_type(trimmed_transaction):





Check first 2 bytes (version and number of inputs)
version_and_inputs = int.from_bytes(trimmed_transaction[:2], byte order='large')

Compare to known sighash values
if version_and_inputs == 0x00000001: 
Check signature
sigh_type = "sigh_1"
elif version_and_inputs == 0x00000002: 
Sign input
sigh_type = "sigh_2"
else:
sigh_type = None
return sigh_type

Example usage
trimmed_transaction = with '\x01\x02'
sighash_type = identify_sighash_type(trimmed_transaction)
print(sighash_type) 
Output: sighash_1

In this example, the identify_sighash_type function takes a trimmed transaction as input and examines its first two bytes to determine which sighash type is required. Based on the comparison to known values ​​(0x00000001 for the check signature and 0x00000002 for the sign input), it returns the identified sighash type.

Conclusion

By following these steps and using the example code provided, you can determine which SIGHASH type needs to be appended to a trimmed transaction at the time of checking the input script. This information is critical to correctly processing Bitcoin transactions and ensuring secure and efficient input script validation.