diff --git a/crypto/src/math/ec/custom/sec/SecT571Field.cs b/crypto/src/math/ec/custom/sec/SecT571Field.cs
index 0711ee4aa..fc84e336b 100644
--- a/crypto/src/math/ec/custom/sec/SecT571Field.cs
+++ b/crypto/src/math/ec/custom/sec/SecT571Field.cs
@@ -59,6 +59,57 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
return z;
}
+ public static void Invert(ulong[] x, ulong[] z)
+ {
+ if (Nat576.IsZero64(x))
+ throw new InvalidOperationException();
+
+ // Itoh-Tsujii inversion with bases { 2, 3, 5 }
+
+ ulong[] t0 = Nat576.Create64();
+ ulong[] t1 = Nat576.Create64();
+ ulong[] t2 = Nat576.Create64();
+
+ Square(x, t2);
+
+ // 5 | 570
+ Square(t2, t0);
+ Square(t0, t1);
+ Multiply(t0, t1, t0);
+ SquareN(t0, 2, t1);
+ Multiply(t0, t1, t0);
+ Multiply(t0, t2, t0);
+
+ // 3 | 114
+ SquareN(t0, 5, t1);
+ Multiply(t0, t1, t0);
+ SquareN(t1, 5, t1);
+ Multiply(t0, t1, t0);
+
+ // 2 | 38
+ SquareN(t0, 15, t1);
+ Multiply(t0, t1, t2);
+
+ // ! {2,3,5} | 19
+ SquareN(t2, 30, t0);
+ SquareN(t0, 30, t1);
+ Multiply(t0, t1, t0);
+
+ // 3 | 9
+ SquareN(t0, 60, t1);
+ Multiply(t0, t1, t0);
+ SquareN(t1, 60, t1);
+ Multiply(t0, t1, t0);
+
+ // 3 | 3
+ SquareN(t0, 180, t1);
+ Multiply(t0, t1, t0);
+ SquareN(t1, 180, t1);
+ Multiply(t0, t1, t0);
+
+ Multiply(t0, t2, z);
+ }
+
public static void Multiply(ulong[] x, ulong[] y, ulong[] z)
{
ulong[] tt = Nat576.CreateExt64();
@@ -199,7 +250,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec
protected static void ImplMulwAcc(ulong[] xs, ulong y, ulong[] z, int zOff)
{
ulong[] u = new ulong[32];
- // u[0] = 0;
+ //u[0] = 0;
u[1] = y;
for (int i = 2; i < 32; i += 2)
{
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