Provide some extra methods on ECFieldElement to avoid full conversion to

BigInteger for common, simple tests

6 files changed, 71 insertions, 61 deletions

diff --git a/core/src/main/java/org/bouncycastle/asn1/ua/DSTU4145PointEncoder.java b/core/src/main/java/org/bouncycastle/asn1/ua/DSTU4145PointEncoder.java
index 0227d2ad..41b50d04 100644
--- a/core/src/main/java/org/bouncycastle/asn1/ua/DSTU4145PointEncoder.java
+++ b/core/src/main/java/org/bouncycastle/asn1/ua/DSTU4145PointEncoder.java
@@ -38,26 +38,23 @@ public abstract class DSTU4145PointEncoder
      * @return the solution for <code>z<sup>2</sup> + z = beta</code> or
      *         <code>null</code> if no solution exists.
      */
-    private static ECFieldElement solveQuadradicEquation(ECFieldElement beta)
+    private static ECFieldElement solveQuadraticEquation(ECCurve curve, ECFieldElement beta)
     {
-        ECFieldElement.F2m b = (ECFieldElement.F2m)beta;
-        ECFieldElement zeroElement = new ECFieldElement.F2m(
-            b.getM(), b.getK1(), b.getK2(), b.getK3(), ECConstants.ZERO);
-
-        if (beta.toBigInteger().equals(ECConstants.ZERO))
+        if (beta.isZero())
         {
-            return zeroElement;
+            return beta;
         }
 
+        ECFieldElement zeroElement = curve.fromBigInteger(ECConstants.ZERO);
+
         ECFieldElement z = null;
-        ECFieldElement gamma = zeroElement;
+        ECFieldElement gamma = null;
 
         Random rand = new Random();
-        int m = b.getM();
+        int m = beta.getFieldSize();
         do
         {
-            ECFieldElement t = new ECFieldElement.F2m(b.getM(), b.getK1(),
-                b.getK2(), b.getK3(), new BigInteger(m, rand));
+            ECFieldElement t = curve.fromBigInteger(new BigInteger(m, rand));
             z = zeroElement;
             ECFieldElement w = beta;
             for (int i = 1; i <= m - 1; i++)
@@ -66,13 +63,13 @@ public abstract class DSTU4145PointEncoder
                 z = z.square().add(w2.multiply(t));
                 w = w2.add(beta);
             }
-            if (!w.toBigInteger().equals(ECConstants.ZERO))
+            if (!w.isZero())
             {
                 return null;
             }
             gamma = z.square().add(z);
         }
-        while (gamma.toBigInteger().equals(ECConstants.ZERO));
+        while (gamma.isZero());
 
         return z;
     }
@@ -94,7 +91,7 @@ public abstract class DSTU4145PointEncoder
         int byteCount = converter.getByteLength(Q.getX());
         byte[] bytes = converter.integerToBytes(Q.getX().toBigInteger(), byteCount);
 
-        if (!(Q.getX().toBigInteger().equals(ECConstants.ZERO)))
+        if (!Q.getX().isZero())
         {
             ECFieldElement y = Q.getY().multiply(Q.getX().invert());
             if (trace(y).equals(ECConstants.ONE))
@@ -129,13 +126,12 @@ public abstract class DSTU4145PointEncoder
             bytes = Arrays.clone(bytes);
             bytes[bytes.length - 1] ^= 0x01;
         }
-        ECCurve.F2m c = (ECCurve.F2m)curve;
         ECFieldElement xp = curve.fromBigInteger(new BigInteger(1, bytes));
         ECFieldElement yp = null;
-        if (xp.toBigInteger().equals(ECConstants.ZERO))
+        if (xp.isZero())
         {
             yp = (ECFieldElement.F2m)curve.getB();
-            for (int i = 0; i < c.getM() - 1; i++)
+            for (int i = 0; i < curve.getFieldSize() - 1; i++)
             {
                 yp = yp.square();
             }
@@ -144,7 +140,7 @@ public abstract class DSTU4145PointEncoder
         {
             ECFieldElement beta = xp.add(curve.getA()).add(
                 curve.getB().multiply(xp.square().invert()));
-            ECFieldElement z = solveQuadradicEquation(beta);
+            ECFieldElement z = solveQuadraticEquation(curve, beta);
             if (z == null)
             {
                 throw new RuntimeException("Invalid point compression");
diff --git a/core/src/main/java/org/bouncycastle/crypto/signers/DSTU4145Signer.java b/core/src/main/java/org/bouncycastle/crypto/signers/DSTU4145Signer.java
index a8fc194e..a12e4012 100644
--- a/core/src/main/java/org/bouncycastle/crypto/signers/DSTU4145Signer.java
+++ b/core/src/main/java/org/bouncycastle/crypto/signers/DSTU4145Signer.java
@@ -57,7 +57,7 @@ public class DSTU4145Signer
     public BigInteger[] generateSignature(byte[] message)
     {
         ECFieldElement h = hash2FieldElement(key.getParameters().getCurve(), message);
-        if (h.toBigInteger().signum() == 0)
+        if (h.isZero())
         {
             h = key.getParameters().getCurve().fromBigInteger(ONE);
         }
@@ -74,7 +74,7 @@ public class DSTU4145Signer
                     e = generateRandomInteger(key.getParameters().getN(), random);
                     Fe = key.getParameters().getG().multiply(e).getX();
                 }
-                while (Fe.toBigInteger().signum() == 0);
+                while (Fe.isZero());
 
                 y = h.multiply(Fe);
                 r = fieldElement2Integer(key.getParameters().getN(), y);
@@ -100,7 +100,7 @@ public class DSTU4145Signer
         }
 
         ECFieldElement h = hash2FieldElement(key.getParameters().getCurve(), message);
-        if (h.toBigInteger().signum() == 0)
+        if (h.isZero())
         {
             h = key.getParameters().getCurve().fromBigInteger(ONE);
         }
diff --git a/core/src/main/java/org/bouncycastle/math/ec/ECCurve.java b/core/src/main/java/org/bouncycastle/math/ec/ECCurve.java
index 58281af7..63a5f19b 100644
--- a/core/src/main/java/org/bouncycastle/math/ec/ECCurve.java
+++ b/core/src/main/java/org/bouncycastle/math/ec/ECCurve.java
@@ -148,9 +148,7 @@ public abstract class ECCurve
             }
 
             BigInteger betaValue = beta.toBigInteger();
-            int bit0 = betaValue.testBit(0) ? 1 : 0;
-
-            if (bit0 != yTilde)
+            if (betaValue.testBit(0) != (yTilde == 1))
             {
                 // Use the other root
                 beta = fromBigInteger(q.subtract(betaValue));
@@ -432,10 +430,7 @@ public abstract class ECCurve
          */
         public boolean isKoblitz()
         {
-            return ((n != null) && (h != null) &&
-                    ((a.toBigInteger().equals(ECConstants.ZERO)) ||
-                    (a.toBigInteger().equals(ECConstants.ONE))) &&
-                    (b.toBigInteger().equals(ECConstants.ONE)));
+            return n != null && h != null && a.bitLength() <= 1 && b.bitLength() == 1;
         }
 
         /**
@@ -480,7 +475,7 @@ public abstract class ECCurve
         {
             ECFieldElement xp = fromBigInteger(X1);
             ECFieldElement yp = null;
-            if (xp.toBigInteger().equals(ECConstants.ZERO))
+            if (X1.signum() == 0)
             {
                 yp = (ECFieldElement.F2m)b;
                 for (int i = 0; i < m - 1; i++)
@@ -491,13 +486,12 @@ public abstract class ECCurve
             else
             {
                 ECFieldElement beta = xp.add(a).add(b.multiply(xp.square().invert()));
-                ECFieldElement z = solveQuadradicEquation(beta);
+                ECFieldElement z = solveQuadraticEquation(beta);
                 if (z == null)
                 {
                     throw new IllegalArgumentException("Invalid point compression");
                 }
-                int zBit = z.toBigInteger().testBit(0) ? 1 : 0;
-                if (zBit != yTilde)
+                if (z.testBitZero() != (yTilde == 1))
                 {
                     z = z.add(fromBigInteger(ECConstants.ONE));
                 }
@@ -512,28 +506,26 @@ public abstract class ECCurve
          * D.1.6) The other solution is <code>z + 1</code>.
          * 
          * @param beta
-         *            The value to solve the qradratic equation for.
+         *            The value to solve the quadratic equation for.
          * @return the solution for <code>z<sup>2</sup> + z = beta</code> or
          *         <code>null</code> if no solution exists.
          */
-        private ECFieldElement solveQuadradicEquation(ECFieldElement beta)
+        private ECFieldElement solveQuadraticEquation(ECFieldElement beta)
         {
-            ECFieldElement zeroElement = new ECFieldElement.F2m(
-                    this.m, this.k1, this.k2, this.k3, ECConstants.ZERO);
-
-            if (beta.toBigInteger().equals(ECConstants.ZERO))
+            if (beta.isZero())
             {
-                return zeroElement;
+                return beta;
             }
 
+            ECFieldElement zeroElement = fromBigInteger(ECConstants.ZERO);
+
             ECFieldElement z = null;
-            ECFieldElement gamma = zeroElement;
+            ECFieldElement gamma = null;
 
             Random rand = new Random();
             do
             {
-                ECFieldElement t = new ECFieldElement.F2m(this.m, this.k1,
-                        this.k2, this.k3, new BigInteger(m, rand));
+                ECFieldElement t = fromBigInteger(new BigInteger(m, rand));
                 z = zeroElement;
                 ECFieldElement w = beta;
                 for (int i = 1; i <= m - 1; i++)
@@ -542,13 +534,13 @@ public abstract class ECCurve
                     z = z.square().add(w2.multiply(t));
                     w = w2.add(beta);
                 }
-                if (!w.toBigInteger().equals(ECConstants.ZERO))
+                if (!w.isZero())
                 {
                     return null;
                 }
                 gamma = z.square().add(z);
             }
-            while (gamma.toBigInteger().equals(ECConstants.ZERO));
+            while (gamma.isZero());
 
             return z;
         }
diff --git a/core/src/main/java/org/bouncycastle/math/ec/ECFieldElement.java b/core/src/main/java/org/bouncycastle/math/ec/ECFieldElement.java
index b5e9aa55..10a0fd35 100644
--- a/core/src/main/java/org/bouncycastle/math/ec/ECFieldElement.java
+++ b/core/src/main/java/org/bouncycastle/math/ec/ECFieldElement.java
@@ -19,6 +19,21 @@ public abstract class ECFieldElement
     public abstract ECFieldElement invert();
     public abstract ECFieldElement sqrt();
 
+    public int bitLength()
+    {
+        return toBigInteger().bitLength();
+    }
+
+    public boolean isZero()
+    {
+        return 0 == toBigInteger().signum();
+    }
+
+    public boolean testBitZero()
+    {
+        return toBigInteger().testBit(0);
+    }
+
     public String toString()
     {
         return this.toBigInteger().toString(2);
@@ -925,7 +940,21 @@ public abstract class ECFieldElement
             {
                 this.representation = PPB;
             }
+        }
+
+        public int bitLength()
+        {
+            return x.bitLength();
+        }
 
+        public boolean isZero()
+        {
+            return x.isZero();
+        }
+
+        public boolean testBitZero()
+        {
+            return !x.isZero() && x.testBit(0);
         }
 
         public BigInteger toBigInteger()
diff --git a/core/src/main/java/org/bouncycastle/math/ec/ECPoint.java b/core/src/main/java/org/bouncycastle/math/ec/ECPoint.java
index cbc5aaf4..ff0dc33a 100644
--- a/core/src/main/java/org/bouncycastle/math/ec/ECPoint.java
+++ b/core/src/main/java/org/bouncycastle/math/ec/ECPoint.java
@@ -401,10 +401,9 @@ public abstract class ECPoint
                 // bit of y * x^(-1)
                 // if ypTilde = 0, then PC := 02, else PC := 03
                 // Note: PC === PO[0]
-                if (!(this.getX().toBigInteger().equals(ECConstants.ZERO)))
+                if (!this.getX().isZero())
                 {
-                    if (this.getY().multiply(this.getX().invert())
-                            .toBigInteger().testBit(0))
+                    if (this.getY().multiply(this.getX().invert()).testBitZero())
                     {
                         // ypTilde = 1, hence PC = 03
                         PO[0] = 0x03;
@@ -545,7 +544,7 @@ public abstract class ECPoint
                 return this;
             }
 
-            if (this.x.toBigInteger().signum() == 0) 
+            if (this.x.isZero()) 
             {
                 // if x1 == 0, then (x1, y1) == (x1, x1 + y1)
                 // and hence this = -this and thus 2(x1, y1) == infinity
diff --git a/core/src/main/java/org/bouncycastle/math/ec/Tnaf.java b/core/src/main/java/org/bouncycastle/math/ec/Tnaf.java
index af4355f3..03fc4da0 100644
--- a/core/src/main/java/org/bouncycastle/math/ec/Tnaf.java
+++ b/core/src/main/java/org/bouncycastle/math/ec/Tnaf.java
@@ -415,23 +415,17 @@ class Tnaf
      */
     public static byte getMu(ECCurve.F2m curve)
     {
-        BigInteger a = curve.getA().toBigInteger();
-        byte mu;
-
-        if (a.equals(ECConstants.ZERO))
-        {
-            mu = -1;
-        }
-        else if (a.equals(ECConstants.ONE))
+        if (!curve.isKoblitz())
         {
-            mu = 1;
+            throw new IllegalArgumentException("No Koblitz curve (ABC), TNAF multiplication not possible");
         }
-        else
+
+        if (curve.getA().isZero())
         {
-            throw new IllegalArgumentException("No Koblitz curve (ABC), " +
-                    "TNAF multiplication not possible");
+            return -1;
         }
-        return mu;
+
+        return 1;
     }
 
     /**