using System; using Org.BouncyCastle.Math; using Org.BouncyCastle.Math.EC; using Org.BouncyCastle.Utilities; namespace Org.BouncyCastle.Asn1.X9 { /** * ASN.1 def for Elliptic-Curve Curve structure. See * X9.62, for further details. */ public class X9Curve : Asn1Encodable { private readonly ECCurve curve; private readonly byte[] seed; private readonly DerObjectIdentifier fieldIdentifier; public X9Curve( ECCurve curve) : this(curve, null) { } public X9Curve( ECCurve curve, byte[] seed) { if (curve == null) throw new ArgumentNullException("curve"); this.curve = curve; this.seed = Arrays.Clone(seed); if (ECAlgorithms.IsFpCurve(curve)) { this.fieldIdentifier = X9ObjectIdentifiers.PrimeField; } else if (ECAlgorithms.IsF2mCurve(curve)) { this.fieldIdentifier = X9ObjectIdentifiers.CharacteristicTwoField; } else { throw new ArgumentException("This type of ECCurve is not implemented"); } } [Obsolete("Use constructor including order/cofactor")] public X9Curve( X9FieldID fieldID, Asn1Sequence seq) : this(fieldID, null, null, seq) { } public X9Curve( X9FieldID fieldID, BigInteger order, BigInteger cofactor, Asn1Sequence seq) { if (fieldID == null) throw new ArgumentNullException("fieldID"); if (seq == null) throw new ArgumentNullException("seq"); this.fieldIdentifier = fieldID.Identifier; if (fieldIdentifier.Equals(X9ObjectIdentifiers.PrimeField)) { BigInteger p = ((DerInteger)fieldID.Parameters).Value; BigInteger A = new BigInteger(1, Asn1OctetString.GetInstance(seq[0]).GetOctets()); BigInteger B = new BigInteger(1, Asn1OctetString.GetInstance(seq[1]).GetOctets()); curve = new FpCurve(p, A, B, order, cofactor); } else if (fieldIdentifier.Equals(X9ObjectIdentifiers.CharacteristicTwoField)) { // Characteristic two field DerSequence parameters = (DerSequence)fieldID.Parameters; int m = ((DerInteger)parameters[0]).IntValueExact; DerObjectIdentifier representation = (DerObjectIdentifier)parameters[1]; int k1 = 0; int k2 = 0; int k3 = 0; if (representation.Equals(X9ObjectIdentifiers.TPBasis)) { // Trinomial basis representation k1 = ((DerInteger)parameters[2]).IntValueExact; } else { // Pentanomial basis representation DerSequence pentanomial = (DerSequence) parameters[2]; k1 = ((DerInteger)pentanomial[0]).IntValueExact; k2 = ((DerInteger)pentanomial[1]).IntValueExact; k3 = ((DerInteger)pentanomial[2]).IntValueExact; } BigInteger A = new BigInteger(1, Asn1OctetString.GetInstance(seq[0]).GetOctets()); BigInteger B = new BigInteger(1, Asn1OctetString.GetInstance(seq[1]).GetOctets()); curve = new F2mCurve(m, k1, k2, k3, A, B, order, cofactor); } else { throw new ArgumentException("This type of ECCurve is not implemented"); } if (seq.Count == 3) { seed = ((DerBitString)seq[2]).GetBytes(); } } public ECCurve Curve { get { return curve; } } public byte[] GetSeed() { return Arrays.Clone(seed); } /** * Produce an object suitable for an Asn1OutputStream. *
         *  Curve ::= Sequence {
         *      a               FieldElement,
         *      b               FieldElement,
         *      seed            BIT STRING      OPTIONAL
         *  }
         * 
*/ public override Asn1Object ToAsn1Object() { Asn1EncodableVector v = new Asn1EncodableVector(); if (fieldIdentifier.Equals(X9ObjectIdentifiers.PrimeField) || fieldIdentifier.Equals(X9ObjectIdentifiers.CharacteristicTwoField)) { v.Add(new X9FieldElement(curve.A).ToAsn1Object()); v.Add(new X9FieldElement(curve.B).ToAsn1Object()); } if (seed != null) { v.Add(new DerBitString(seed)); } return new DerSequence(v); } } }