X9FieldElement.cs :  » PDF » iTextSharp » Org » BouncyCastle » Asn1 » X9 » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;

namespace Org.BouncyCastle.Asn1.X9{
    /**
     * Class for processing an ECFieldElement as a DER object.
     */
    public class X9FieldElement
        : Asn1Encodable
    {
    private ECFieldElement f;

    public X9FieldElement(
      ECFieldElement f)
    {
      this.f = f;
    }

    public X9FieldElement(
      BigInteger    p,
      Asn1OctetString  s)
      : this(new FpFieldElement(p, new BigInteger(1, s.GetOctets())))
    {
    }

    public X9FieldElement(
      int        m,
      int        k1,
      int        k2,
      int        k3,
      Asn1OctetString  s)
      : this(new F2mFieldElement(m, k1, k2, k3, new BigInteger(1, s.GetOctets())))
    {
    }

    public ECFieldElement Value
        {
            get { return f; }
        }

    /**
     * Produce an object suitable for an Asn1OutputStream.
     * <pre>
     *  FieldElement ::= OCTET STRING
     * </pre>
     * <p>
     * <ol>
     * <li> if <i>q</i> is an odd prime then the field element is
     * processed as an Integer and converted to an octet string
     * according to x 9.62 4.3.1.</li>
     * <li> if <i>q</i> is 2<sup>m</sup> then the bit string
     * contained in the field element is converted into an octet
     * string with the same ordering padded at the front if necessary.
     * </li>
     * </ol>
     * </p>
     */
    public override Asn1Object ToAsn1Object()
    {
      int byteCount = X9IntegerConverter.GetByteLength(f);
      byte[] paddedBigInteger = X9IntegerConverter.IntegerToBytes(f.ToBigInteger(), byteCount);

      return new DerOctetString(paddedBigInteger);
    }
    }
}