Pattern 3 (P2SH-P2WPKH) Verification Report

Overview

This document verifies the successful implementation of Pattern 3: P2SH-P2WPKH (BIP49 Nested SegWit) single-signature transactions.

Issue Reference

• Issue: #362 - P2SH-P2WPKH transaction validation failure
• Fix: PR #363 - Implement P2SH-P2WPKH (BIP49) support with BIP143 compliance
• Verification Date: 2026-01-15

Test Environment

Component	Value
Network	Bitcoin Regtest (local)
Test Script	scripts/operation/btc/e2e/e2e-p3-p2sh-p2wpkh-singlesig.sh
Command	make btc-e2e-reset P=3

Test Results

✅ All Phases Completed Successfully

1. Infrastructure Setup

   • Database container started and healthy
   • Bitcoin nodes (watch, keygen) started and healthy

2. Wallet Configuration

   • Bitcoin Core wallets created successfully
   • RPC endpoints configured correctly

3. Key Generation

   • HD keys generated for keygen wallet (client, deposit, payment, stored)
   • BIP49 derivation path used: m/49'/1'/account'/change/index

4. Descriptor Export/Import

   • Descriptors exported from keygen wallet
   • Format: sh(wpkh([fingerprint/49'/1'/1']tpub.../0/*))
   • Descriptors imported into watch wallet
   • 2000 addresses generated (1000 per descriptor: receive + change)

5. P2SH-P2WPKH Address Creation

   • Address format verified: 2... (P2SH format in regtest)
   • Sample address: 2N3r5aBFJWBGavJpX7HNpaFRoZWWdyr1jTd

6. Test UTXO Generation

   • 101 blocks generated to payment address
   • Coinbase maturity achieved (100 confirmations)
   • Balance verified: 50.00000000 BTC

7. Payment Request Creation

   • 3 payment requests created successfully
   • Sender address: 2N3r5aBFJWBGavJpX7HNpaFRoZWWdyr1jTd (P2SH format verified)
   • Receiver addresses generated (P2SH-SegWit format for testing)

8. Transaction Creation and Signing

   • ✅ Unsigned transaction created: payment_1_unsigned_0_1768471249785717000.psbt
   • ✅ Transaction signed with keygen wallet (single signature)
   • ✅ Signed transaction: payment_1_signed_0_1768471249856265000.psbt

9. Transaction Broadcast

   • ✅ Transaction sent successfully
   • ✅ Transaction ID: 5b17761f9ea9f5cee3f5a613b368d4a69128cf8177df817ee4d842fc2580bcd7
   • ✅ Transaction accepted into mempool

Technical Verification

BIP143 Compliance

The implementation correctly follows BIP143 (Segregated Witness Transaction Signature Verification):

1. ScriptCode Construction: P2PKH format for signature hash calculation

   OP_DUP OP_HASH160 <20-byte-pubkey-hash> OP_EQUALVERIFY OP_CHECKSIG

2. Signature Hash Calculation: Uses CalcWitnessSigHash with correct scriptCode

3. PSBT Finalization: Custom finalizeP2SHP2WPKHInput() function

   • ScriptSig: Contains redeemScript (P2WPKH script)
   • Witness: [<signature>, <pubkey>]

Key Implementation Files

File	Changes
internal/infrastructure/api/btc/btc/descriptor.go	Added deriveP2WPKHRedeemScript() for sh(wpkh(...)) descriptors
internal/infrastructure/api/btc/btc/psbt.go	BIP143-compliant signing and finalizeP2SHP2WPKHInput() finalization

Descriptor Format Verified

Descriptor: sh(wpkh([5ff97435/49'/1'/1']tpubDDhYwcV7NpBCsKUG6mU2L5qL8GBHwucnpYig9ziE7yWEzLzYQtJDgy3JatAqfRyxedR2A7p1CijnkV1LasdY3XAx9HGBcnv9DDgDw54TtNn/0/*))

Components:
- Type: sh(wpkh(...)) - P2SH-wrapped P2WPKH
- Derivation: [5ff97435/49'/1'/1'] - BIP49 path for testnet account 1
- Extended Pubkey: tpubDD...
- Range: /0/* - Receive addresses (0-999)

Address Format Verified

Expected: 2... (P2SH format in regtest)
Actual:   2N3r5aBFJWBGavJpX7HNpaFRoZWWdyr1jTd ✅

Address Type Breakdown:
- Prefix: 2 (P2SH in regtest/testnet)
- Contains: SegWit P2WPKH script (OP_0 <20-byte-hash>)
- Backward Compatible: Can receive from any wallet

Comparison with Other Patterns

Aspect	Pattern 1 (P2PKH)	Pattern 3 (P2SH-P2WPKH)	Pattern 5 (P2WPKH)
BIP	BIP44	BIP49	BIP84
Address	m.../n...	2...	tb1q...
SegWit	No	Yes (wrapped)	Yes (native)
Legacy Compatible	Yes	Yes	No
Transaction Size	Largest	Medium	Smallest
Status	✅ Working	✅ Working	✅ Working

Root Cause Analysis (Issue #362)

Original Problem

Transaction validation was failing with:

mandatory-script-verify-flag-failed (Script evaluated without error but
finished with a false/empty top stack element)

Root Cause

The original implementation was missing proper PSBT finalization for P2SH-P2WPKH:

1. ScriptSig construction was incorrect
2. Witness serialization was not properly implemented
3. Custom finalization function was needed to work around btcd limitations

Solution (PR #363)

Implemented finalizeP2SHP2WPKHInput() function that:

1. ✅ Properly constructs scriptSig with redeemScript
2. ✅ Correctly serializes witness as [<signature>, <pubkey>]
3. ✅ Uses ScriptBuilder for proper length prefixing
4. ✅ Clears partial signatures after finalization

Conclusion

✅ Pattern 3 (P2SH-P2WPKH Single-sig) is fully implemented and verified

• BIP143 compliance confirmed
• BIP49 derivation path working correctly
• Transactions create, sign, and broadcast successfully
• Address format matches specification (2... for regtest)
• E2E test passes completely without errors

References

• BIP16: Pay to Script Hash (P2SH)
• BIP49: Derivation scheme for P2WPKH-nested-in-P2SH based accounts
• BIP141: Segregated Witness (Consensus layer)
• BIP143: Transaction Signature Verification for Version 0 Witness Program
• Issue #362: https://github.com/hiromaily/go-crypto-wallet/issues/362
• PR #363: https://github.com/hiromaily/go-crypto-wallet/pull/363