From acb1d767e8ca0e575d1777f872aaec483ff4bbe8 Mon Sep 17 00:00:00 2001
From: Craig Raw <craigraw@gmail.com>
Date: Tue, 8 Oct 2024 10:31:23 +0200
Subject: [PATCH] add helper method to multiply a public key

---
 .../java/com/sparrowwallet/drongo/OutputDescriptor.java     | 2 +-
 src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java    | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/sparrowwallet/drongo/OutputDescriptor.java b/src/main/java/com/sparrowwallet/drongo/OutputDescriptor.java
index f222d98..490dc69 100644
--- a/src/main/java/com/sparrowwallet/drongo/OutputDescriptor.java
+++ b/src/main/java/com/sparrowwallet/drongo/OutputDescriptor.java
@@ -575,7 +575,7 @@ public class OutputDescriptor {
         return builder.toString();
     }
 
-    private List<ExtendedKey> sortExtendedPubKeys(Collection<ExtendedKey> keys) {
+    public List<ExtendedKey> sortExtendedPubKeys(Collection<ExtendedKey> keys) {
         List<ExtendedKey> sortedKeys = new ArrayList<>(keys);
         if(mapChildrenDerivations == null || mapChildrenDerivations.isEmpty() || mapChildrenDerivations.containsKey(null)) {
             return sortedKeys;
diff --git a/src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java b/src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java
index 676e193..9db942a 100644
--- a/src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java
+++ b/src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java
@@ -326,6 +326,12 @@ public class ECKey {
         return pub.get();
     }
 
+    /** Multiply the public point by the provided private key */
+    public ECKey multiply(BigInteger privKey) {
+        ECPoint point = pub.get().multiply(privKey);
+        return ECKey.fromPublicOnly(point, false);
+    }
+
     /**
      * Gets the private key in the form of an integer field element. The public key is derived by performing EC
      * point addition this number of times (i.e. point multiplying).