Bitcoin: Is there a helper method to confirm PSBTs?

Confirming Properly Formatted Private Sector Blockchain Transactions (PSBTs) Using Base64

In the world of cryptocurrencies, private sector blockchain transactions (PSBTs) are a crucial aspect of securing and verifying financial transactions. However, as the use of Bitcoin and other cryptocurrencies increases, it becomes increasingly important to pay attention to the correct formatting of PSBTs.

What makes a PSBT properly formatted?

A properly formatted PSBT consists of a header with several fields, including the public key, transaction data, and metadata. Here is a breakdown of each field:

• Public Key: A 256-bit hexadecimal string representing the recipient’s public key.

• Transaction Data: A variable-length array of unsigned integers representing the transaction amount, fee, and other relevant data.

• Metadata

  : A fixed-length byte array containing metadata such as the sender’s identifier (public key) and the hash of the previous block.

Base64 encoding: A useful way to verify PSBTs

To verify the formatting of a PSBT, you can use Base64 encoding. Base64 is a widely used encoding scheme that converts binary data into text strings. In Java, you can use the java.util.Base64 class to encode and decode text strings.

Java code example: Verifying a PSBT using Base64

Here is an example of how you can use Java to verify a correctly base64-formatted PSBT:

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class Main {
public static void main(String[] args) throws NoSuchAlgorithmException {
String psbtStr = "your_psbts_string_here"; // replace with the actual PSBT string
byte[] decodedBase64Bytes = Base64.getDecoder().decode(psbtStr);
MessageDigest digest = MessageDigest.getInstance("SHA-256");
String formattedPsbt = digest.digest(decodedBase64Bytes).toString();
// compare with expected output
String expectedOutput = "your_expected_output_here"; // replace with actual expected output
if (!formattedPsbt.equals(expectedOutput)) {
System.out.println("PSBT is not formatted correctly.");
} else {
System.out.println("PSBT is correctly formatted.");
}
}
}

Library/method for verifying PSBTs in Java

To simplify the verification process, you can use a library like com.github.snookbase64 or create your own custom method. Here is an example using a custom method:

import com.github.snookbase64.Base64Util;
public class Main {
public static void main(String[] args) throws NoSuchAlgorithmException {
String psbtStr = "your_psbts_string_here"; // replace with the actual PSBT string
byte[] decodedBase64Bytes = Base64Util.decode(psbtStr);
boolean is correctly formatted = true;
for (int i = 0; i < decodedBase64Bytes.length; i += 4) {
int publicKeyLength = Math.min(32, decodedBase64Bytes[i] / 256);
if (decodedBase64Bytes[i + publicKeyLength] != (Byte) 255 || !Base64Util.decode(psbtStr.substring(i + 1, i + publicKeyLength + 1)).equals(Base64Util.decode(psbtStr.substring(i + publicKeyLength + 2)))) {
isProperlyFormatted = false;
}
}
System.out.println(isProperlyFormatted ? "PSBT is properly formatted." : "PSBT is not properly formatted.");
}
}

In this example, we check the length of the public key and make sure the transaction data matches the expected output.

Conclusion

Checking the formatting of a PSBT can be a challenging task, especially when working with Base64 encoding. However, using libraries like com.github.snookbase64 or creating custom methods can simplify the process.