From 0b3b1a5c3f45e1c81cdc15ea565c194ef615f814 Mon Sep 17 00:00:00 2001
From: Craig Raw <craigraw@gmail.com>
Date: Wed, 10 Sep 2025 13:10:22 +0200
Subject: [PATCH] align input pubkey retrieval to silent payments reference
 implementation

---
 .../silentpayments/SilentPaymentUtils.java    | 52 +++++++++++++++++--
 1 file changed, 47 insertions(+), 5 deletions(-)

diff --git a/src/main/java/com/sparrowwallet/drongo/silentpayments/SilentPaymentUtils.java b/src/main/java/com/sparrowwallet/drongo/silentpayments/SilentPaymentUtils.java
index 3f0fe2a..aa4322a 100644
--- a/src/main/java/com/sparrowwallet/drongo/silentpayments/SilentPaymentUtils.java
+++ b/src/main/java/com/sparrowwallet/drongo/silentpayments/SilentPaymentUtils.java
@@ -10,13 +10,21 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
 public class SilentPaymentUtils {
     private static final Logger log = LoggerFactory.getLogger(SilentPaymentUtils.class);
 
-    private static final List<ScriptType> SCRIPT_TYPES = List.of(ScriptType.P2TR, ScriptType.P2WPKH, ScriptType.P2SH_P2WPKH, ScriptType.P2PKH);
+    private static final List<ScriptType> SCRIPT_TYPES = List.of(ScriptType.P2TR, ScriptType.P2WPKH, ScriptType.P2SH, ScriptType.P2PKH);
+
+    //Alternative generator point on the secp256k1 curve (x-coordinate) generated from the SHA256 hash of "The scalar for this x is unknown"
+    private static final byte[] NUMS_H = {
+            (byte) 0x50, (byte) 0x92, (byte) 0x9b, (byte) 0x74, (byte) 0xc1, (byte) 0xa0, (byte) 0x49, (byte) 0x54, (byte) 0xb7, (byte) 0x8b, (byte) 0x4b, (byte) 0x60,
+            (byte) 0x35, (byte) 0xe9, (byte) 0x7a, (byte) 0x5e, (byte) 0x07, (byte) 0x8a, (byte) 0x5a, (byte) 0x0f, (byte) 0x28, (byte) 0xec, (byte) 0x96, (byte) 0xd5,
+            (byte) 0x47, (byte) 0xbf, (byte) 0xee, (byte) 0x9a, (byte) 0xce, (byte) 0x80, (byte) 0x3a, (byte) 0xc0
+    };
 
     public static boolean isEligible(Transaction tx, Map<HashIndex, Script> spentScriptPubKeys) {
         if(!containsTaprootOutput(tx)) {
@@ -46,21 +54,55 @@ public class SilentPaymentUtils {
                 if(scriptType.isScriptType(scriptPubKey)) {
                     switch(scriptType) {
                         case P2TR:
-                            keys.add(ScriptType.P2TR.getPublicKeyFromScript(scriptPubKey));
+                            if(input.getWitness() != null && input.getWitness().getPushCount() >= 1) {
+                                List<byte[]> stack = input.getWitness().getPushes();
+                                if(stack.size() > 1 && stack.getLast().length > 0 && stack.getLast()[0] == 0x50) {  //Last item is annex
+                                    stack = stack.subList(0, stack.size() - 1);
+                                }
+
+                                if(stack.size() > 1) {
+                                    // Script path spend
+                                    byte[] controlBlock = stack.getLast();
+                                    // Control block is <control byte> <32 byte internal key> and 0 or more <32 byte hash>
+                                    if(controlBlock.length >= 33) {
+                                        byte[] internalKey = Arrays.copyOfRange(controlBlock, 1, 33);
+                                        if(Arrays.equals(internalKey, NUMS_H)) {
+                                            break;
+                                        }
+                                    }
+                                }
+
+                                ECKey pubKey = ScriptType.P2TR.getPublicKeyFromScript(scriptPubKey);
+                                if(pubKey.isCompressed()) {
+                                    keys.add(pubKey);
+                                }
+                            }
+                            break;
+                        case P2SH:
+                            Script redeemScript = input.getScriptSig().getFirstNestedScript();
+                            if(ScriptType.P2WPKH.isScriptType(redeemScript)) {
+                                if(input.getWitness() != null && input.getWitness().getPushCount() == 2) {
+                                    byte[] pubKey = input.getWitness().getPushes().getLast();
+                                    if(pubKey != null && pubKey.length == 33) {
+                                        keys.add(ECKey.fromPublicOnly(pubKey));
+                                    }
+                                }
+                            }
                             break;
                         case P2WPKH:
-                        case P2SH_P2WPKH:
                             if(input.getWitness() != null && input.getWitness().getPushCount() == 2) {
-                                byte[] pubKey = input.getWitness().getPushes().get(input.getWitness().getPushCount() - 1);
+                                byte[] pubKey = input.getWitness().getPushes().getLast();
                                 if(pubKey != null && pubKey.length == 33) {
                                     keys.add(ECKey.fromPublicOnly(pubKey));
                                 }
                             }
                             break;
                         case P2PKH:
+                            byte[] spkHash = ScriptType.P2PKH.getHashFromScript(scriptPubKey);
                             for(ScriptChunk scriptChunk : input.getScriptSig().getChunks()) {
-                                if(scriptChunk.isPubKey() && scriptChunk.getData().length == 33) {
+                                if(scriptChunk.isPubKey() && scriptChunk.getData().length == 33 && Arrays.equals(Utils.sha256hash160(scriptChunk.getData()), spkHash)) {
                                     keys.add(scriptChunk.getPubKey());
+                                    break;
                                 }
                             }
                             break;