Fix field reduction for custom secp128r1 curve

- see https://github.com/bcgit/bc-java/issues/566

1 files changed, 5 insertions, 0 deletions

diff --git a/crypto/src/math/ec/custom/sec/SecP128R1Field.cs b/crypto/src/math/ec/custom/sec/SecP128R1Field.cs

index d1ac009b3..cf91c7e5d 100644
--- a/crypto/src/math/ec/custom/sec/SecP128R1Field.cs
+++ b/crypto/src/math/ec/custom/sec/SecP128R1Field.cs
@@ -134,6 +134,11 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
 
                 x = (uint)c;
             }
+
+            if (z[3] >= P3 && Nat128.Gte(z, P))
+            {
+                AddPInvTo(z);
+            }
         }
 
         public static void Square(uint[] x, uint[] z)