1 files changed, 102 insertions, 0 deletions
diff --git a/Crypto/src/asn1/x9/X9FieldID.cs b/Crypto/src/asn1/x9/X9FieldID.cs
new file mode 100644
index 000000000..c51cc4df2
--- /dev/null
+++ b/Crypto/src/asn1/x9/X9FieldID.cs
@@ -0,0 +1,102 @@
+using Org.BouncyCastle.Math;
+
+namespace Org.BouncyCastle.Asn1.X9
+{
+ /**
+ * ASN.1 def for Elliptic-Curve Field ID structure. See
+ * X9.62, for further details.
+ */
+ public class X9FieldID
+ : Asn1Encodable
+ {
+ private readonly DerObjectIdentifier id;
+ private readonly Asn1Object parameters;
+
+ /**
+ * Constructor for elliptic curves over prime fields
+ * <code>F<sub>2</sub></code>.
+ * @param primeP The prime <code>p</code> defining the prime field.
+ */
+ public X9FieldID(
+ BigInteger primeP)
+ {
+ this.id = X9ObjectIdentifiers.PrimeField;
+ this.parameters = new DerInteger(primeP);
+ }
+
+ /**
+ * Constructor for elliptic curves over binary fields
+ * <code>F<sub>2<sup>m</sup></sub></code>.
+ * @param m The exponent <code>m</code> of
+ * <code>F<sub>2<sup>m</sup></sub></code>.
+ * @param k1 The integer <code>k1</code> where <code>x<sup>m</sup> +
+ * x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
+ * represents the reduction polynomial <code>f(z)</code>.
+ * @param k2 The integer <code>k2</code> where <code>x<sup>m</sup> +
+ * x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
+ * represents the reduction polynomial <code>f(z)</code>.
+ * @param k3 The integer <code>k3</code> where <code>x<sup>m</sup> +
+ * x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
+ * represents the reduction polynomial <code>f(z)</code>..
+ */
+ public X9FieldID(
+ int m,
+ int k1,
+ int k2,
+ int k3)
+ {
+ this.id = X9ObjectIdentifiers.CharacteristicTwoField;
+
+ Asn1EncodableVector fieldIdParams = new Asn1EncodableVector(new DerInteger(m));
+
+ if (k2 == 0)
+ {
+ fieldIdParams.Add(
+ X9ObjectIdentifiers.TPBasis,
+ new DerInteger(k1));
+ }
+ else
+ {
+ fieldIdParams.Add(
+ X9ObjectIdentifiers.PPBasis,
+ new DerSequence(
+ new DerInteger(k1),
+ new DerInteger(k2),
+ new DerInteger(k3)));
+ }
+
+ this.parameters = new DerSequence(fieldIdParams);
+ }
+
+ internal X9FieldID(
+ Asn1Sequence seq)
+ {
+ this.id = (DerObjectIdentifier) seq[0];
+ this.parameters = (Asn1Object) seq[1];
+ }
+
+ public DerObjectIdentifier Identifier
+ {
+ get { return id; }
+ }
+
+ public Asn1Object Parameters
+ {
+ get { return parameters; }
+ }
+
+ /**
+ * Produce a Der encoding of the following structure.
+ * <pre>
+ * FieldID ::= Sequence {
+ * fieldType FIELD-ID.&id({IOSet}),
+ * parameters FIELD-ID.&Type({IOSet}{@fieldType})
+ * }
+ * </pre>
+ */
+ public override Asn1Object ToAsn1Object()
+ {
+ return new DerSequence(id, parameters);
+ }
+ }
+}
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