verify_transaction

Verify Transaction (using SPV and BEEF) Example

This example demonstrates how to use the spv and transaction packages to perform a comprehensive verification of a transaction, including its scripts and Merkle proof (from BEEF data).

Overview

The verify_transaction example showcases:

1. Starting with a hexadecimal string representing BEEF data (which includes the transaction and its Merkle path).
2. Creating a transaction.Transaction object from this hex string using transaction.NewTransactionFromBEEFHex.
3. Calling the spv.Verify function to perform a series of checks.
4. Using spv.GullibleHeadersClient as a placeholder for actual block header validation.

The spv.Verify function typically checks:

• The internal consistency and validity of the BEEF structure.
• The syntactic validity of the transaction's input and output scripts.
• The correctness of the Merkle path against the transaction ID (i.e., the transaction is correctly placed in its purported Merkle tree).
• (Optionally) Fee verification if a FeeVerifier is provided.
• Confirmation of the Merkle root against a block header obtained via the spv.Headers client.

Code Walkthrough

Verifying the Transaction

// BEEF data as a hex string (truncated for brevity)
const BEEFHex = "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"

// Create transaction from BEEF hex
tx, err := transaction.NewTransactionFromBEEFHex(BEEFHex)
if err != nil {
    panic(err)
}

// Perform SPV verification
// This checks BEEF structure, script validity, Merkle path,
// and (conceptually) block header confirmation.
// GullibleHeadersClient trusts any header. No FeeVerifier is provided.
verified, _ := spv.Verify(tx, &spv.GullibleHeadersClient{}, nil)
println(verified)

This section shows loading a transaction from BEEF hex. The spv.Verify function is then called. It uses the MerklePath embedded within the tx object (which comes from the BEEF data) and the provided spv.Headers client.

Because spv.GullibleHeadersClient is used, the block header check will always pass. Thus, verified will be true if the BEEF structure is valid, the transaction scripts are syntactically correct, and the Merkle path correctly proves the transaction's inclusion in some Merkle tree. It does not, with this client, confirm that the transaction is in a block on the actual main chain.

Running the Example

To run this example:

go run verify_transaction.go

The output will be true if the transaction passes all checks relative to the GullibleHeadersClient (i.e., scripts are valid, Merkle proof is internally consistent).

Note:

• The example uses a hardcoded BEEF hex string.
• spv.GullibleHeadersClient is used for simplicity. For true SPV, a headers_client.Client connected to a real headers service should be used.
• A FeeVerifier (the third argument to spv.Verify) can be provided to check if the transaction pays adequate fees, but it's nil in this example.

Integration Steps

To integrate transaction verification into your application:

1. Obtain the transaction data, preferably in BEEF format (hex or binary) to include the Merkle proof.
2. Create a transaction.Transaction object (e.g., using transaction.NewTransactionFromBEEFHex()).
3. Initialize a proper spv.Headers client, like headers_client.Client, configured for your network and a trusted headers source.
4. (Optional) Create and configure a FeeVerifier if you need to check transaction fees.
5. Call spv.Verify(yourTransaction, yourHeadersClient, yourFeeVerifier).
   • A true result indicates the transaction is valid, confirmed, and (if applicable) meets fee requirements according to your provided clients.
   • A false result or an error indicates a failure in one of the verification steps.

Additional Resources

For more information, see:

• Package Documentation - SPV
• Package Documentation - Transaction
• Package Documentation - Headers Client
• Verify BEEF Example
• Validate SPV Example