1 files changed, 163 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/asn1/x9/X9Curve.java b/core/src/main/java/org/spongycastle/asn1/x9/X9Curve.java
new file mode 100644
index 00000000..f2d2976c
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/asn1/x9/X9Curve.java
@@ -0,0 +1,163 @@
+package org.spongycastle.asn1.x9;
+
+import java.math.BigInteger;
+
+import org.spongycastle.asn1.ASN1EncodableVector;
+import org.spongycastle.asn1.ASN1Integer;
+import org.spongycastle.asn1.ASN1Object;
+import org.spongycastle.asn1.ASN1ObjectIdentifier;
+import org.spongycastle.asn1.ASN1OctetString;
+import org.spongycastle.asn1.ASN1Primitive;
+import org.spongycastle.asn1.ASN1Sequence;
+import org.spongycastle.asn1.DERBitString;
+import org.spongycastle.asn1.DERSequence;
+import org.spongycastle.math.ec.ECAlgorithms;
+import org.spongycastle.math.ec.ECCurve;
+
+/**
+ * ASN.1 def for Elliptic-Curve Curve structure. See
+ * X9.62, for further details.
+ */
+public class X9Curve
+    extends ASN1Object
+    implements X9ObjectIdentifiers
+{
+    private ECCurve     curve;
+    private byte[]      seed;
+    private ASN1ObjectIdentifier fieldIdentifier = null;
+
+    public X9Curve(
+        ECCurve     curve)
+    {
+        this.curve = curve;
+        this.seed = null;
+        setFieldIdentifier();
+    }
+
+    public X9Curve(
+        ECCurve     curve,
+        byte[]      seed)
+    {
+        this.curve = curve;
+        this.seed = seed;
+        setFieldIdentifier();
+    }
+
+    public X9Curve(
+        X9FieldID     fieldID,
+        ASN1Sequence  seq)
+    {
+        // TODO Is it possible to get the order(n) and cofactor(h) too?
+
+        fieldIdentifier = fieldID.getIdentifier();
+        if (fieldIdentifier.equals(prime_field))
+        {
+            BigInteger      p = ((ASN1Integer)fieldID.getParameters()).getValue();
+            X9FieldElement  x9A = new X9FieldElement(p, (ASN1OctetString)seq.getObjectAt(0));
+            X9FieldElement  x9B = new X9FieldElement(p, (ASN1OctetString)seq.getObjectAt(1));
+            curve = new ECCurve.Fp(p, x9A.getValue().toBigInteger(), x9B.getValue().toBigInteger());
+        }
+        else if (fieldIdentifier.equals(characteristic_two_field)) 
+        {
+            // Characteristic two field
+            ASN1Sequence parameters = ASN1Sequence.getInstance(fieldID.getParameters());
+            int m = ((ASN1Integer)parameters.getObjectAt(0)).getValue().
+                intValue();
+            ASN1ObjectIdentifier representation
+                = (ASN1ObjectIdentifier)parameters.getObjectAt(1);
+
+            int k1 = 0;
+            int k2 = 0;
+            int k3 = 0;
+
+            if (representation.equals(tpBasis)) 
+            {
+                // Trinomial basis representation
+                k1 = ASN1Integer.getInstance(parameters.getObjectAt(2)).getValue().intValue();
+            }
+            else if (representation.equals(ppBasis))
+            {
+                // Pentanomial basis representation
+                ASN1Sequence pentanomial = ASN1Sequence.getInstance(parameters.getObjectAt(2));
+                k1 = ASN1Integer.getInstance(pentanomial.getObjectAt(0)).getValue().intValue();
+                k2 = ASN1Integer.getInstance(pentanomial.getObjectAt(1)).getValue().intValue();
+                k3 = ASN1Integer.getInstance(pentanomial.getObjectAt(2)).getValue().intValue();
+            }
+            else
+            {
+                throw new IllegalArgumentException("This type of EC basis is not implemented");
+            }
+            X9FieldElement x9A = new X9FieldElement(m, k1, k2, k3, (ASN1OctetString)seq.getObjectAt(0));
+            X9FieldElement x9B = new X9FieldElement(m, k1, k2, k3, (ASN1OctetString)seq.getObjectAt(1));
+            curve = new ECCurve.F2m(m, k1, k2, k3, x9A.getValue().toBigInteger(), x9B.getValue().toBigInteger());
+        }
+        else
+        {
+            throw new IllegalArgumentException("This type of ECCurve is not implemented");
+        }
+
+        if (seq.size() == 3)
+        {
+            seed = ((DERBitString)seq.getObjectAt(2)).getBytes();
+        }
+    }
+
+    private void setFieldIdentifier()
+    {
+        if (ECAlgorithms.isFpCurve(curve))
+        {
+            fieldIdentifier = prime_field;
+        }
+        else if (ECAlgorithms.isF2mCurve(curve))
+        {
+            fieldIdentifier = characteristic_two_field;
+        }
+        else
+        {
+            throw new IllegalArgumentException("This type of ECCurve is not implemented");
+        }
+    }
+
+    public ECCurve  getCurve()
+    {
+        return curve;
+    }
+
+    public byte[]   getSeed()
+    {
+        return seed;
+    }
+
+    /**
+     * Produce an object suitable for an ASN1OutputStream.
+     * <pre>
+     *  Curve ::= SEQUENCE {
+     *      a               FieldElement,
+     *      b               FieldElement,
+     *      seed            BIT STRING      OPTIONAL
+     *  }
+     * </pre>
+     */
+    public ASN1Primitive toASN1Primitive()
+    {
+        ASN1EncodableVector v = new ASN1EncodableVector();
+
+        if (fieldIdentifier.equals(prime_field)) 
+        { 
+            v.add(new X9FieldElement(curve.getA()).toASN1Primitive());
+            v.add(new X9FieldElement(curve.getB()).toASN1Primitive());
+        } 
+        else if (fieldIdentifier.equals(characteristic_two_field)) 
+        {
+            v.add(new X9FieldElement(curve.getA()).toASN1Primitive());
+            v.add(new X9FieldElement(curve.getB()).toASN1Primitive());
+        }
+
+        if (seed != null)
+        {
+            v.add(new DERBitString(seed));
+        }
+
+        return new DERSequence(v);
+    }
+}