/// <summary>
/// Creates an elliptic curve with the specified elliptic field
/// {@code field}, the coefficients {@code a} and
/// {@code b}, and the {@code seed} used for curve generation. </summary>
/// <param name="field"> the finite field that this elliptic curve is over. </param>
/// <param name="a"> the first coefficient of this elliptic curve. </param>
/// <param name="b"> the second coefficient of this elliptic curve. </param>
/// <param name="seed"> the bytes used during curve generation for later
/// validation. Contents of this array are copied to protect against
/// subsequent modification. </param>
/// <exception cref="NullPointerException"> if {@code field},
/// {@code a}, or {@code b} is null. </exception>
/// <exception cref="IllegalArgumentException"> if {@code a}
/// or {@code b} is not null and not in {@code field}. </exception>
public EllipticCurve(ECField field, System.Numerics.BigInteger a, System.Numerics.BigInteger b, sbyte[] seed)
{
if (field == null)
{
throw new NullPointerException("field is null");
}
if (a == null)
{
throw new NullPointerException("first coefficient is null");
}
if (b == null)
{
throw new NullPointerException("second coefficient is null");
}
CheckValidity(field, a, "first coefficient");
CheckValidity(field, b, "second coefficient");
this.Field_Renamed = field;
this.a = a;
this.b = b;
if (seed != null)
{
this.Seed_Renamed = seed.clone();
}
else
{
this.Seed_Renamed = null;
}
}
// Check coefficient c is a valid element in ECField field.
private static void CheckValidity(ECField field, System.Numerics.BigInteger c, String cName)
{
// can only perform check if field is ECFieldFp or ECFieldF2m.
if (field is ECFieldFp)
{
System.Numerics.BigInteger p = ((ECFieldFp)field).P;
if (p.CompareTo(c) != 1)
{
throw new IllegalArgumentException(cName + " is too large");
}
else if (c.signum() < 0)
{
throw new IllegalArgumentException(cName + " is negative");
}
}
else if (field is ECFieldF2m)
{
int m = ((ECFieldF2m)field).M;
if (c.bitLength() > m)
{
throw new IllegalArgumentException(cName + " is too large");
}
}
}
/// <summary>
/// Creates an elliptic curve with the specified elliptic field
/// {@code field} and the coefficients {@code a} and
/// {@code b}. </summary>
/// <param name="field"> the finite field that this elliptic curve is over. </param>
/// <param name="a"> the first coefficient of this elliptic curve. </param>
/// <param name="b"> the second coefficient of this elliptic curve. </param>
/// <exception cref="NullPointerException"> if {@code field},
/// {@code a}, or {@code b} is null. </exception>
/// <exception cref="IllegalArgumentException"> if {@code a}
/// or {@code b} is not null and not in {@code field}. </exception>
public EllipticCurve(ECField field, System.Numerics.BigInteger a, System.Numerics.BigInteger b) : this(field, a, b, null)
{
}
