diff --git a/crypto/src/math/ec/custom/sec/SecT409Field.cs b/crypto/src/math/ec/custom/sec/SecT409Field.cs
index d71f5b5f9..84eada96e 100644
--- a/crypto/src/math/ec/custom/sec/SecT409Field.cs
+++ b/crypto/src/math/ec/custom/sec/SecT409Field.cs
@@ -47,6 +47,57 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
return z;
}
+ public static void Invert(ulong[] x, ulong[] z)
+ {
+ if (Nat448.IsZero64(x))
+ throw new InvalidOperationException();
+
+ // Itoh-Tsujii inversion with bases { 2, 3 }
+
+ ulong[] t0 = Nat448.Create64();
+ ulong[] t1 = Nat448.Create64();
+ ulong[] t2 = Nat448.Create64();
+
+ Square(x, t0);
+
+ // 3 | 408
+ SquareN(t0, 1, t1);
+ Multiply(t0, t1, t0);
+ SquareN(t1, 1, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 136
+ SquareN(t0, 3, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 68
+ SquareN(t0, 6, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 34
+ SquareN(t0, 12, t1);
+ Multiply(t0, t1, t2);
+
+ // ! {2,3} | 17
+ SquareN(t2, 24, t0);
+ SquareN(t0, 24, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 8
+ SquareN(t0, 48, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 4
+ SquareN(t0, 96, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 2
+ SquareN(t0, 192, t1);
+ Multiply(t0, t1, t0);
+
+ Multiply(t0, t2, z);
+ }
+
public static void Multiply(ulong[] x, ulong[] y, ulong[] z)
{
ulong[] tt = Nat448.CreateExt64();
@@ -196,7 +247,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
Debug.Assert(y >> 59 == 0);
ulong[] u = new ulong[8];
- // u[0] = 0;
+ //u[0] = 0;
u[1] = y;
u[2] = u[1] << 1;
u[3] = u[2] ^ y;
|
