diff --git a/crypto/src/math/ec/ECAlgorithms.cs b/crypto/src/math/ec/ECAlgorithms.cs
index be4fd1b14..06288132b 100644
--- a/crypto/src/math/ec/ECAlgorithms.cs
+++ b/crypto/src/math/ec/ECAlgorithms.cs
@@ -1,93 +1,105 @@
using System;
-using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.Field;
namespace Org.BouncyCastle.Math.EC
{
- public class ECAlgorithms
- {
- public static ECPoint SumOfTwoMultiplies(ECPoint P, BigInteger a,
- ECPoint Q, BigInteger b)
- {
- ECCurve c = P.Curve;
- if (!c.Equals(Q.Curve))
- throw new ArgumentException("P and Q must be on same curve");
+ public class ECAlgorithms
+ {
+ public static bool IsF2mCurve(ECCurve c)
+ {
+ IFiniteField field = c.Field;
+ return field.Dimension > 1 && field.Characteristic.Equals(BigInteger.Two)
+ && field is IPolynomialExtensionField;
+ }
- // Point multiplication for Koblitz curves (using WTNAF) beats Shamir's trick
- if (c is F2mCurve)
- {
- F2mCurve f2mCurve = (F2mCurve) c;
- if (f2mCurve.IsKoblitz)
- {
- return P.Multiply(a).Add(Q.Multiply(b));
- }
- }
+ public static bool IsFpCurve(ECCurve c)
+ {
+ return c.Field.Dimension == 1;
+ }
- return ImplShamirsTrick(P, a, Q, b);
- }
+ public static ECPoint SumOfTwoMultiplies(ECPoint P, BigInteger a,
+ ECPoint Q, BigInteger b)
+ {
+ ECCurve c = P.Curve;
+ if (!c.Equals(Q.Curve))
+ throw new ArgumentException("P and Q must be on same curve");
- /*
- * "Shamir's Trick", originally due to E. G. Straus
- * (Addition chains of vectors. American Mathematical Monthly,
- * 71(7):806-808, Aug./Sept. 1964)
- *
- * Input: The points P, Q, scalar k = (km?, ... , k1, k0)
- * and scalar l = (lm?, ... , l1, l0).
- * Output: R = k * P + l * Q.
- * 1: Z <- P + Q
- * 2: R <- O
- * 3: for i from m-1 down to 0 do
- * 4: R <- R + R {point doubling}
- * 5: if (ki = 1) and (li = 0) then R <- R + P end if
- * 6: if (ki = 0) and (li = 1) then R <- R + Q end if
- * 7: if (ki = 1) and (li = 1) then R <- R + Z end if
- * 8: end for
- * 9: return R
- */
- public static ECPoint ShamirsTrick(
- ECPoint P,
- BigInteger k,
- ECPoint Q,
- BigInteger l)
- {
- if (!P.Curve.Equals(Q.Curve))
- throw new ArgumentException("P and Q must be on same curve");
+ // Point multiplication for Koblitz curves (using WTNAF) beats Shamir's trick
+ if (c is F2mCurve)
+ {
+ F2mCurve f2mCurve = (F2mCurve) c;
+ if (f2mCurve.IsKoblitz)
+ {
+ return P.Multiply(a).Add(Q.Multiply(b));
+ }
+ }
- return ImplShamirsTrick(P, k, Q, l);
- }
+ return ImplShamirsTrick(P, a, Q, b);
+ }
- private static ECPoint ImplShamirsTrick(ECPoint P, BigInteger k,
- ECPoint Q, BigInteger l)
- {
- int m = System.Math.Max(k.BitLength, l.BitLength);
- ECPoint Z = P.Add(Q);
- ECPoint R = P.Curve.Infinity;
+ /*
+ * "Shamir's Trick", originally due to E. G. Straus
+ * (Addition chains of vectors. American Mathematical Monthly,
+ * 71(7):806-808, Aug./Sept. 1964)
+ *
+ * Input: The points P, Q, scalar k = (km?, ... , k1, k0)
+ * and scalar l = (lm?, ... , l1, l0).
+ * Output: R = k * P + l * Q.
+ * 1: Z <- P + Q
+ * 2: R <- O
+ * 3: for i from m-1 down to 0 do
+ * 4: R <- R + R {point doubling}
+ * 5: if (ki = 1) and (li = 0) then R <- R + P end if
+ * 6: if (ki = 0) and (li = 1) then R <- R + Q end if
+ * 7: if (ki = 1) and (li = 1) then R <- R + Z end if
+ * 8: end for
+ * 9: return R
+ */
+ public static ECPoint ShamirsTrick(
+ ECPoint P,
+ BigInteger k,
+ ECPoint Q,
+ BigInteger l)
+ {
+ if (!P.Curve.Equals(Q.Curve))
+ throw new ArgumentException("P and Q must be on same curve");
- for (int i = m - 1; i >= 0; --i)
- {
- R = R.Twice();
+ return ImplShamirsTrick(P, k, Q, l);
+ }
- if (k.TestBit(i))
- {
- if (l.TestBit(i))
- {
- R = R.Add(Z);
- }
- else
- {
- R = R.Add(P);
- }
- }
- else
- {
- if (l.TestBit(i))
- {
- R = R.Add(Q);
- }
- }
- }
+ private static ECPoint ImplShamirsTrick(ECPoint P, BigInteger k,
+ ECPoint Q, BigInteger l)
+ {
+ int m = System.Math.Max(k.BitLength, l.BitLength);
+ ECPoint Z = P.Add(Q);
+ ECPoint R = P.Curve.Infinity;
- return R;
- }
- }
+ for (int i = m - 1; i >= 0; --i)
+ {
+ R = R.Twice();
+
+ if (k.TestBit(i))
+ {
+ if (l.TestBit(i))
+ {
+ R = R.Add(Z);
+ }
+ else
+ {
+ R = R.Add(P);
+ }
+ }
+ else
+ {
+ if (l.TestBit(i))
+ {
+ R = R.Add(Q);
+ }
+ }
+ }
+
+ return R;
+ }
+ }
}
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