From 4f256c2f1bc119b208f9d35d847bf4c5b8072a5e Mon Sep 17 00:00:00 2001
From: Peter Dettman <peter.dettman@bouncycastle.org>
Date: Wed, 12 Mar 2014 18:28:37 +0700
Subject: Add GLVMultiplier and supporting interfaces

---
 .../org/bouncycastle/math/ec/ECEndomorphism.java   |  8 +++++
 .../org/bouncycastle/math/ec/GLVEndomorphism.java  |  8 +++++
 .../org/bouncycastle/math/ec/GLVMultiplier.java    | 40 ++++++++++++++++++++++
 3 files changed, 56 insertions(+)
 create mode 100644 core/src/main/java/org/bouncycastle/math/ec/ECEndomorphism.java
 create mode 100644 core/src/main/java/org/bouncycastle/math/ec/GLVEndomorphism.java
 create mode 100644 core/src/main/java/org/bouncycastle/math/ec/GLVMultiplier.java

(limited to 'core/src/main/java/org')

diff --git a/core/src/main/java/org/bouncycastle/math/ec/ECEndomorphism.java b/core/src/main/java/org/bouncycastle/math/ec/ECEndomorphism.java
new file mode 100644
index 00000000..110bd2ab
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/math/ec/ECEndomorphism.java
@@ -0,0 +1,8 @@
+package org.bouncycastle.math.ec;
+
+public interface ECEndomorphism
+{
+    ECPointMap getPointMap();
+
+    boolean hasEfficientPointMap();
+}
diff --git a/core/src/main/java/org/bouncycastle/math/ec/GLVEndomorphism.java b/core/src/main/java/org/bouncycastle/math/ec/GLVEndomorphism.java
new file mode 100644
index 00000000..bf576908
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/math/ec/GLVEndomorphism.java
@@ -0,0 +1,8 @@
+package org.bouncycastle.math.ec;
+
+import java.math.BigInteger;
+
+public interface GLVEndomorphism extends ECEndomorphism
+{
+    BigInteger[] decomposeScalar(BigInteger k);
+}
diff --git a/core/src/main/java/org/bouncycastle/math/ec/GLVMultiplier.java b/core/src/main/java/org/bouncycastle/math/ec/GLVMultiplier.java
new file mode 100644
index 00000000..4a6b2343
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/math/ec/GLVMultiplier.java
@@ -0,0 +1,40 @@
+package org.bouncycastle.math.ec;
+
+import java.math.BigInteger;
+
+public class GLVMultiplier extends AbstractECMultiplier
+{
+    protected final ECCurve curve;
+    protected final GLVEndomorphism glvEndomorphism;
+
+    public GLVMultiplier(ECCurve curve, GLVEndomorphism glvEndomorphism)
+    {
+        if (curve == null || curve.getOrder() == null)
+        {
+            throw new IllegalArgumentException("Need curve with known group order");
+        }
+
+        this.curve = curve;
+        this.glvEndomorphism = glvEndomorphism;
+    }
+
+    protected ECPoint multiplyPositive(ECPoint p, BigInteger k)
+    {
+        if (!curve.equals(p.getCurve()))
+        {
+            throw new IllegalStateException();
+        }
+
+        BigInteger n = p.getCurve().getOrder();
+        BigInteger[] ab = glvEndomorphism.decomposeScalar(k.mod(n));
+        BigInteger a = ab[0], b = ab[1];
+
+        ECPointMap pointMap = glvEndomorphism.getPointMap();
+        if (glvEndomorphism.hasEfficientPointMap())
+        {
+            return ECAlgorithms.implShamirsTrickWNaf(p, a, pointMap, b);
+        }
+
+        return ECAlgorithms.implShamirsTrickWNaf(p, a, pointMap.map(p), b);
+    }
+}
-- 
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