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, 15 insertions, 0 deletions

diff --git a/crypto/src/util/Integers.cs b/crypto/src/util/Integers.cs
index e746b0ef4..bd05a053e 100644
--- a/crypto/src/util/Integers.cs
+++ b/crypto/src/util/Integers.cs
@@ -4,6 +4,21 @@ namespace Org.BouncyCastle.Utilities
 {
     public abstract class Integers
     {
+        public static int NumberOfLeadingZeros(int i)
+        {
+            if (i <= 0)
+                return (~i >> (31 - 5)) & (1 << 5);
+
+            uint u = (uint)i;
+            int n = 1;
+            if (0 == (u >> 16)) { n += 16; u <<= 16; }
+            if (0 == (u >> 24)) { n +=  8; u <<=  8; }
+            if (0 == (u >> 28)) { n +=  4; u <<=  4; }
+            if (0 == (u >> 30)) { n +=  2; u <<=  2; }
+            n -= (int)(u >> 31);
+            return n;
+        }
+
         public static int RotateLeft(int i, int distance)
         {
             return (i << distance) ^ (int)((uint)i >> -distance);