EC updates from bc-java

- use half-trace when possible (odd m) for decompression/validation
- provide field-specific half-trace methods for custom curves
- clarify the logic of point-order testing for binary curves
- expand test cases for invalid points

1 files changed, 12 insertions, 0 deletions

diff --git a/crypto/src/math/ec/custom/sec/SecT571FieldElement.cs b/crypto/src/math/ec/custom/sec/SecT571FieldElement.cs
index c9f3aa5c0..22edfe0a2 100644
--- a/crypto/src/math/ec/custom/sec/SecT571FieldElement.cs
+++ b/crypto/src/math/ec/custom/sec/SecT571FieldElement.cs
@@ -150,6 +150,18 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
             return new SecT571FieldElement(z);
         }
 
+        public override ECFieldElement HalfTrace()
+        {
+            ulong[] z = Nat576.Create64();
+            SecT571Field.HalfTrace(x, z);
+            return new SecT571FieldElement(z);
+        }
+
+        public override bool HasFastTrace
+        {
+            get { return true; }
+        }
+
         public override int Trace()
         {
             return (int)SecT571Field.Trace(x);