Merge pull request #3938

01cc978 ringct: remove an unnecessary scalarmultBase in zeroCommit (moneromooo-monero)

3 files changed, 12 insertions, 4 deletions

diff --git a/src/ringct/rctOps.cpp b/src/ringct/rctOps.cpp
index cc46d0aa7..68cc43128 100644
--- a/src/ringct/rctOps.cpp
+++ b/src/ringct/rctOps.cpp
@@ -134,12 +134,9 @@ namespace rct {
     }
     
     key zeroCommit(xmr_amount amount) {
-        key mask = identity();
-        mask = scalarmultBase(mask);
         key am = d2h(amount);
         key bH = scalarmultH(am);
-        addKeys(mask, mask, bH);
-        return mask;
+        return addKeys(G, bH);
     }
 
     key commit(xmr_amount amount, const key &mask) {
diff --git a/src/ringct/rctOps.h b/src/ringct/rctOps.h
index 3f8f6955c..f8889af5c 100644
--- a/src/ringct/rctOps.h
+++ b/src/ringct/rctOps.h
@@ -62,6 +62,7 @@ namespace rct {
     static const key Z = { {0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00  } };
     static const key I = { {0x01, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00 , 0x00, 0x00, 0x00,0x00  } };
     static const key L = { {0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10 } };
+    static const key G = { {0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66 } };
 
     //Creates a zero scalar
     inline key zero() { return Z; }
diff --git a/tests/unit_tests/ringct.cpp b/tests/unit_tests/ringct.cpp
index b7fcbbcab..0f4bd3edf 100644
--- a/tests/unit_tests/ringct.cpp
+++ b/tests/unit_tests/ringct.cpp
@@ -1061,3 +1061,13 @@ TEST(ringct, key_ostream)
     out.str()
   );
 }
+
+TEST(ringct, zeroCommmit)
+{
+  static const uint64_t amount = crypto::rand<uint64_t>();
+  const rct::key z = rct::zeroCommit(amount);
+  const rct::key a = rct::scalarmultBase(rct::identity());
+  const rct::key b = rct::scalarmultH(rct::d2h(amount));
+  const rct::key manual = rct::addKeys(a, b);
+  ASSERT_EQ(z, manual);
+}