Cache-safety for EC lookup tables

- creation of cache-safe lookup tables delegated to ECCurve
- FixedPointCombMultiplier uses cache-safe lookup table
- FixedPointCombMultiplier avoids BigInteger.TestBit

1 files changed, 61 insertions, 2 deletions

diff --git a/crypto/src/math/ec/custom/sec/SecT571K1Curve.cs b/crypto/src/math/ec/custom/sec/SecT571K1Curve.cs
index f5806f09c..3d84797f7 100644
--- a/crypto/src/math/ec/custom/sec/SecT571K1Curve.cs
+++ b/crypto/src/math/ec/custom/sec/SecT571K1Curve.cs
@@ -1,6 +1,7 @@
 using System;
 
 using Org.BouncyCastle.Math.EC.Multiplier;
+using Org.BouncyCastle.Math.Raw;
 using Org.BouncyCastle.Utilities.Encoders;
 
 namespace Org.BouncyCastle.Math.EC.Custom.Sec
@@ -8,7 +9,8 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
     internal class SecT571K1Curve
         : AbstractF2mCurve
     {
-        private const int SecT571K1_DEFAULT_COORDS = COORD_LAMBDA_PROJECTIVE;
+        private const int SECT571K1_DEFAULT_COORDS = COORD_LAMBDA_PROJECTIVE;
+        private const int SECT571K1_FE_LONGS = 9;
 
         protected readonly SecT571K1Point m_infinity;
 
@@ -22,7 +24,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
             this.m_order = new BigInteger(1, Hex.Decode("020000000000000000000000000000000000000000000000000000000000000000000000131850E1F19A63E4B391A8DB917F4138B630D84BE5D639381E91DEB45CFE778F637C1001"));
             this.m_cofactor = BigInteger.ValueOf(4);
 
-            this.m_coord = SecT571K1_DEFAULT_COORDS;
+            this.m_coord = SECT571K1_DEFAULT_COORDS;
         }
 
         protected override ECCurve CloneCurve()
@@ -100,5 +102,62 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
         {
             get { return 10; }
         }
+
+        public override ECLookupTable CreateCacheSafeLookupTable(ECPoint[] points, int off, int len)
+        {
+            ulong[] table = new ulong[len * SECT571K1_FE_LONGS * 2];
+            {
+                int pos = 0;
+                for (int i = 0; i < len; ++i)
+                {
+                    ECPoint p = points[off + i];
+                    Nat576.Copy64(((SecT571FieldElement)p.RawXCoord).x, 0, table, pos); pos += SECT571K1_FE_LONGS;
+                    Nat576.Copy64(((SecT571FieldElement)p.RawYCoord).x, 0, table, pos); pos += SECT571K1_FE_LONGS;
+                }
+            }
+
+            return new SecT571K1LookupTable(this, table, len);
+        }
+
+        private class SecT571K1LookupTable
+            : ECLookupTable
+        {
+            private readonly SecT571K1Curve m_outer;
+            private readonly ulong[] m_table;
+            private readonly int m_size;
+
+            internal SecT571K1LookupTable(SecT571K1Curve outer, ulong[] table, int size)
+            {
+                this.m_outer = outer;
+                this.m_table = table;
+                this.m_size = size;
+            }
+
+            public virtual int Size
+            {
+                get { return m_size; }
+            }
+
+            public virtual ECPoint Lookup(int index)
+            {
+                ulong[] x = Nat576.Create64(), y = Nat576.Create64();
+                int pos = 0;
+
+                for (int i = 0; i < m_size; ++i)
+                {
+                    ulong MASK = (ulong)(long)(((i ^ index) - 1) >> 31);
+
+                    for (int j = 0; j < SECT571K1_FE_LONGS; ++j)
+                    {
+                        x[j] ^= m_table[pos + j] & MASK;
+                        y[j] ^= m_table[pos + SECT571K1_FE_LONGS + j] & MASK;
+                    }
+
+                    pos += (SECT571K1_FE_LONGS * 2);
+                }
+
+                return m_outer.CreateRawPoint(new SecT571FieldElement(x), new SecT571FieldElement(y), false);
+            }
+        }
     }
 }