1 files changed, 47 insertions, 0 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256R1Curve.java b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256R1Curve.java
index 5ff6a38d..7d7b51d5 100644
--- a/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256R1Curve.java
+++ b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256R1Curve.java
@@ -4,7 +4,9 @@ import java.math.BigInteger;
 
 import org.bouncycastle.math.ec.ECCurve;
 import org.bouncycastle.math.ec.ECFieldElement;
+import org.bouncycastle.math.ec.ECLookupTable;
 import org.bouncycastle.math.ec.ECPoint;
+import org.bouncycastle.math.raw.Nat256;
 import org.bouncycastle.util.encoders.Hex;
 
 public class SecP256R1Curve extends ECCurve.AbstractFp
@@ -77,4 +79,49 @@ public class SecP256R1Curve extends ECCurve.AbstractFp
     {
         return infinity;
     }
+
+    public ECLookupTable createCacheSafeLookupTable(ECPoint[] points, int off, final int len)
+    {
+        final int FE_INTS = 8;
+
+        final int[] table = new int[len * FE_INTS * 2];
+        {
+            int pos = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                ECPoint p = points[off + i];
+                Nat256.copy(((SecP256R1FieldElement)p.getRawXCoord()).x, 0, table, pos); pos += FE_INTS;
+                Nat256.copy(((SecP256R1FieldElement)p.getRawYCoord()).x, 0, table, pos); pos += FE_INTS;
+            }
+        }
+
+        return new ECLookupTable()
+        {
+            public int getSize()
+            {
+                return len;
+            }
+
+            public ECPoint lookup(int index)
+            {
+                int[] x = Nat256.create(), y = Nat256.create();
+                int pos = 0;
+
+                for (int i = 0; i < len; ++i)
+                {
+                    int MASK = ((i ^ index) - 1) >> 31;
+
+                    for (int j = 0; j < FE_INTS; ++j)
+                    {
+                        x[j] ^= table[pos + j] & MASK;
+                        y[j] ^= table[pos + FE_INTS + j] & MASK;
+                    }
+
+                    pos += (FE_INTS * 2);
+                }
+
+                return createRawPoint(new SecP256R1FieldElement(x), new SecP256R1FieldElement(y), false);
+            }
+        };
+    }
 }