diff --git a/crypto/src/math/ec/ECFieldElement.cs b/crypto/src/math/ec/ECFieldElement.cs
index f31732aaf..93f63a435 100644
--- a/crypto/src/math/ec/ECFieldElement.cs
+++ b/crypto/src/math/ec/ECFieldElement.cs
@@ -138,13 +138,7 @@ namespace Org.BouncyCastle.Math.EC
public override ECFieldElement Subtract(
ECFieldElement b)
{
- BigInteger x2 = b.ToBigInteger();
- BigInteger x3 = x.Subtract(x2);
- if (x3.SignValue < 0)
- {
- x3 = x3.Add(q);
- }
- return new FpFieldElement(q, r, x3);
+ return new FpFieldElement(q, r, ModSubtract(x, b.ToBigInteger()));
}
public override ECFieldElement Multiply(
@@ -156,7 +150,7 @@ namespace Org.BouncyCastle.Math.EC
public override ECFieldElement Divide(
ECFieldElement b)
{
- return new FpFieldElement(q, r, ModMult(x, b.ToBigInteger().ModInverse(q)));
+ return new FpFieldElement(q, r, ModMult(x, ModInverse(b.ToBigInteger())));
}
public override ECFieldElement Negate()
@@ -172,7 +166,7 @@ namespace Org.BouncyCastle.Math.EC
public override ECFieldElement Invert()
{
// TODO Modular inversion can be faster for a (Generalized) Mersenne Prime.
- return new FpFieldElement(q, r, x.ModInverse(q));
+ return new FpFieldElement(q, r, ModInverse(x));
}
// D.1.4 91
@@ -318,6 +312,18 @@ namespace Org.BouncyCastle.Math.EC
return _2x;
}
+ protected virtual BigInteger ModInverse(BigInteger x)
+ {
+ // Our BigInteger.ModInverse performance is quite poor, so use the new Nat/Mod classes here
+ //return x.ModInverse(q);
+ int len = (FieldSize + 31) >> 5;
+ uint[] p = Nat.FromBigInteger(len, q);
+ uint[] n = Nat.FromBigInteger(len, x);
+ uint[] z = Nat.Create(len);
+ Mod.Invert(p, n, z);
+ return Nat.ToBigInteger(len, z);
+ }
+
protected virtual BigInteger ModMult(BigInteger x1, BigInteger x2)
{
return ModReduce(x1.Multiply(x2));
@@ -359,6 +365,16 @@ namespace Org.BouncyCastle.Math.EC
return x;
}
+ protected virtual BigInteger ModSubtract(BigInteger x1, BigInteger x2)
+ {
+ BigInteger x3 = x1.Subtract(x2);
+ if (x3.SignValue < 0)
+ {
+ x3 = x3.Add(q);
+ }
+ return x3;
+ }
+
public override bool Equals(
object obj)
{
@@ -1067,7 +1083,7 @@ namespace Org.BouncyCastle.Math.EC
public override ECFieldElement Multiply(
ECFieldElement b)
{
- // Right-to-left comb multiplication in the IntArray
+ // Right-to-left comb multiplication in the LongArray
// Input: Binary polynomials a(z) and b(z) of degree at most m-1
// Output: c(z) = a(z) * b(z) mod f(z)
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