diff options
Diffstat (limited to 'crypto/src/asn1/x9/X9Curve.cs')
| -rw-r--r-- | crypto/src/asn1/x9/X9Curve.cs | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/crypto/src/asn1/x9/X9Curve.cs b/crypto/src/asn1/x9/X9Curve.cs new file mode 100644 index 000000000..b92e7b3b5 --- /dev/null +++ b/crypto/src/asn1/x9/X9Curve.cs @@ -0,0 +1,147 @@ +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) + { + this.curve = curve; + } + + public X9Curve( + ECCurve curve, + byte[] seed) + { + if (curve == null) + throw new ArgumentNullException("curve"); + + this.curve = curve; + this.seed = Arrays.Clone(seed); + + if (curve is FpCurve) + { + this.fieldIdentifier = X9ObjectIdentifiers.PrimeField; + } + else if (curve is F2mCurve) + { + this.fieldIdentifier = X9ObjectIdentifiers.CharacteristicTwoField; + } + else + { + throw new ArgumentException("This type of ECCurve is not implemented"); + } + } + + public X9Curve( + X9FieldID fieldID, + 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 q = ((DerInteger) fieldID.Parameters).Value; + X9FieldElement x9A = new X9FieldElement(q, (Asn1OctetString) seq[0]); + X9FieldElement x9B = new X9FieldElement(q, (Asn1OctetString) seq[1]); + curve = new FpCurve(q, x9A.Value.ToBigInteger(), x9B.Value.ToBigInteger()); + } + else + { + if (fieldIdentifier.Equals(X9ObjectIdentifiers.CharacteristicTwoField)) + { + // Characteristic two field + DerSequence parameters = (DerSequence)fieldID.Parameters; + int m = ((DerInteger)parameters[0]).Value.IntValue; + 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]).Value.IntValue; + } + else + { + // Pentanomial basis representation + DerSequence pentanomial = (DerSequence) parameters[2]; + k1 = ((DerInteger) pentanomial[0]).Value.IntValue; + k2 = ((DerInteger) pentanomial[1]).Value.IntValue; + k3 = ((DerInteger) pentanomial[2]).Value.IntValue; + } + X9FieldElement x9A = new X9FieldElement(m, k1, k2, k3, (Asn1OctetString)seq[0]); + X9FieldElement x9B = new X9FieldElement(m, k1, k2, k3, (Asn1OctetString)seq[1]); + // TODO Is it possible to get the order (n) and cofactor(h) too? + curve = new F2mCurve(m, k1, k2, k3, x9A.Value.ToBigInteger(), x9B.Value.ToBigInteger()); + } + } + + 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. + * <pre> + * Curve ::= Sequence { + * a FieldElement, + * b FieldElement, + * seed BIT STRING OPTIONAL + * } + * </pre> + */ + 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); + } + } +} |