From 5fe4c66462e6149c2ed3ce24224a7a7b328a2cfa Mon Sep 17 00:00:00 2001
From: Ava Chow <github@achow101.com>
Date: Mon, 29 Jan 2024 17:32:02 -0500
Subject: [PATCH] XOnlyPubKey: Add GetCPubKeys

We need to retrieve the even and odd compressed pubkeys for xonly
pubkeys, so add a function to do that. Also reuse it in GetKeyIDs.
---
 src/pubkey.cpp | 20 +++++++++++++-------
 src/pubkey.h   |  4 ++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/pubkey.cpp b/src/pubkey.cpp
index a4ca9a170a9..6041c89e7f1 100644
--- a/src/pubkey.cpp
+++ b/src/pubkey.cpp
@@ -197,20 +197,26 @@ constexpr XOnlyPubKey XOnlyPubKey::NUMS_H{
     []() consteval { return XOnlyPubKey{"50929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0"_hex_u8}; }(),
 };
 
-std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
+std::vector<CPubKey> XOnlyPubKey::GetCPubKeys() const
 {
-    std::vector<CKeyID> out;
-    // For now, use the old full pubkey-based key derivation logic. As it is indexed by
-    // Hash160(full pubkey), we need to return both a version prefixed with 0x02, and one
-    // with 0x03.
+    std::vector<CPubKey> out;
     unsigned char b[33] = {0x02};
     std::copy(m_keydata.begin(), m_keydata.end(), b + 1);
     CPubKey fullpubkey;
     fullpubkey.Set(b, b + 33);
-    out.push_back(fullpubkey.GetID());
+    out.push_back(fullpubkey);
     b[0] = 0x03;
     fullpubkey.Set(b, b + 33);
-    out.push_back(fullpubkey.GetID());
+    out.push_back(fullpubkey);
+    return out;
+}
+
+std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
+{
+    std::vector<CKeyID> out;
+    for (const CPubKey& pk : GetCPubKeys()) {
+        out.push_back(pk.GetID());
+    }
     return out;
 }
 
diff --git a/src/pubkey.h b/src/pubkey.h
index cbc827dc606..442dc2d6431 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -283,9 +283,13 @@ public:
     std::optional<std::pair<XOnlyPubKey, bool>> CreateTapTweak(const uint256* merkle_root) const;
 
     /** Returns a list of CKeyIDs for the CPubKeys that could have been used to create this XOnlyPubKey.
+     * As the CKeyID is the Hash160(full pubkey), the produced CKeyIDs are for the versions of this
+     * XOnlyPubKey with 0x02 and 0x03 prefixes.
      * This is needed for key lookups since keys are indexed by CKeyID.
      */
     std::vector<CKeyID> GetKeyIDs() const;
+    /** Returns this XOnlyPubKey with 0x02 and 0x03 prefixes */
+    std::vector<CPubKey> GetCPubKeys() const;
 
     CPubKey GetEvenCorrespondingCPubKey() const;