From 11ae28f007e8c932ca11f5351b93e5ebf1a9599a Mon Sep 17 00:00:00 2001
From: Peter Dettman <peter.dettman@bouncycastle.org>
Date: Sat, 3 Aug 2019 00:14:03 +0700
Subject: Improve caching behaviour for algorithms using endomorphisms

---
 crypto/src/math/ec/endo/EndoPreCompInfo.cs | 26 +++++++++++++++++
 crypto/src/math/ec/endo/EndoUtilities.cs   | 47 +++++++++++++++++++++++++++++-
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 crypto/src/math/ec/endo/EndoPreCompInfo.cs

(limited to 'crypto/src/math/ec/endo')

diff --git a/crypto/src/math/ec/endo/EndoPreCompInfo.cs b/crypto/src/math/ec/endo/EndoPreCompInfo.cs
new file mode 100644
index 000000000..cb926fc98
--- /dev/null
+++ b/crypto/src/math/ec/endo/EndoPreCompInfo.cs
@@ -0,0 +1,26 @@
+using System;
+
+using Org.BouncyCastle.Math.EC.Multiplier;
+
+namespace Org.BouncyCastle.Math.EC.Endo
+{
+    public class EndoPreCompInfo
+        : PreCompInfo
+    {
+        protected ECEndomorphism m_endomorphism;
+
+        protected ECPoint m_mappedPoint;
+
+        public virtual ECEndomorphism Endomorphism
+        {
+            get { return m_endomorphism; }
+            set { this.m_endomorphism = value; }
+        }
+
+        public virtual ECPoint MappedPoint
+        {
+            get { return m_mappedPoint; }
+            set { this.m_mappedPoint = value; }
+        }
+    }
+}
diff --git a/crypto/src/math/ec/endo/EndoUtilities.cs b/crypto/src/math/ec/endo/EndoUtilities.cs
index 16916e632..843103bca 100644
--- a/crypto/src/math/ec/endo/EndoUtilities.cs
+++ b/crypto/src/math/ec/endo/EndoUtilities.cs
@@ -1,11 +1,13 @@
 using System;
 
-using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.EC.Multiplier;
 
 namespace Org.BouncyCastle.Math.EC.Endo
 {
     public abstract class EndoUtilities
     {
+        public static readonly string PRECOMP_NAME = "bc_endo";
+
         public static BigInteger[] DecomposeScalar(ScalarSplitParameters p, BigInteger k)
         {
             int bits = p.Bits;
@@ -18,6 +20,13 @@ namespace Org.BouncyCastle.Math.EC.Endo
             return new BigInteger[]{ a, b };
         }
 
+        public static ECPoint MapPoint(ECEndomorphism endomorphism, ECPoint p)
+        {
+            EndoPreCompInfo precomp = (EndoPreCompInfo)p.Curve.Precompute(p, PRECOMP_NAME,
+                new MapPointCallback(endomorphism, p));
+            return precomp.MappedPoint;
+        }
+
         private static BigInteger CalculateB(BigInteger k, BigInteger g, int t)
         {
             bool negative = (g.SignValue < 0);
@@ -30,5 +39,41 @@ namespace Org.BouncyCastle.Math.EC.Endo
             }
             return negative ? b.Negate() : b;
         }
+
+        private class MapPointCallback
+            : IPreCompCallback
+        {
+            private readonly ECEndomorphism m_endomorphism;
+            private readonly ECPoint m_point;
+
+            internal MapPointCallback(ECEndomorphism endomorphism, ECPoint point)
+            {
+                this.m_endomorphism = endomorphism;
+                this.m_point = point;
+            }
+
+            public PreCompInfo Precompute(PreCompInfo existing)
+            {
+                EndoPreCompInfo existingEndo = existing as EndoPreCompInfo;
+
+                if (CheckExisting(existingEndo, m_endomorphism))
+                    return existingEndo;
+
+                ECPoint mappedPoint = m_endomorphism.PointMap.Map(m_point);
+
+                EndoPreCompInfo result = new EndoPreCompInfo();
+                result.Endomorphism = m_endomorphism;
+                result.MappedPoint = mappedPoint;
+                return result;
+            }
+
+            private bool CheckExisting(EndoPreCompInfo existingEndo, ECEndomorphism endomorphism)
+            {
+                return null != existingEndo
+                    && existingEndo.Endomorphism == endomorphism
+                    && existingEndo.MappedPoint != null;
+            }
+
+        }
     }
 }
-- 
cgit 1.5.1