File	Doc	Category	Size	Date	Package
EllipticCurve.java	API Doc	Java SE 5 API	5459	Fri Aug 26 14:57:18 BST 2005	java.security.spec

EllipticCurve

• java.lang.Object

Fields Summary
private final ECField	field
private final BigInteger	a
private final BigInteger	b
private final byte[]	seed

Constructors Summary
public EllipticCurve(ECField field, BigInteger a, BigInteger b) Creates an elliptic curve with the specified elliptic field field and the coefficients a and b. param field the finite field that this elliptic curve is over. param a the first coefficient of this elliptic curve. param b the second coefficient of this elliptic curve. exception NullPointerException if field, a, or b is null. exception IllegalArgumentException if a or b is not null and not in field. this(field, a, b, null);
public EllipticCurve(ECField field, BigInteger a, BigInteger b, byte[] seed) Creates an elliptic curve with the specified elliptic field field, the coefficients a and b, and the seed used for curve generation. param field the finite field that this elliptic curve is over. param a the first coefficient of this elliptic curve. param b the second coefficient of this elliptic curve. param seed the bytes used during curve generation for later validation. Contents of this array are copied to protect against subsequent modification. exception NullPointerException if field, a, or b is null. exception IllegalArgumentException if a or b is not null and not in field. 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 = field; this.a = a; this.b = b; if (seed != null) { this.seed = (byte[]) seed.clone(); } else { this.seed = null; }

Methods Summary
private static void	checkValidity(java.security.spec.ECField field, java.math.BigInteger c, java.lang.String cName) // can only perform check if field is ECFieldFp or ECFieldF2m. if (field instanceof ECFieldFp) { BigInteger p = ((ECFieldFp)field).getP(); if (p.compareTo(c) != 1) { throw new IllegalArgumentException(cName + " is too large"); } else if (c.signum() != 1) { throw new IllegalArgumentException(cName + " is negative"); } } else if (field instanceof ECFieldF2m) { int m = ((ECFieldF2m)field).getM(); if (c.bitLength() > m) { throw new IllegalArgumentException(cName + " is too large"); } }
public boolean	equals(java.lang.Object obj) Compares this elliptic curve for equality with the specified object. param obj the object to be compared. return true if obj is an instance of EllipticCurve and the field, A, B, and seeding bytes match, false otherwise. if (this == obj) return true; if (obj instanceof EllipticCurve) { EllipticCurve curve = (EllipticCurve) obj; if ((field.equals(curve.field)) && (a.equals(curve.a)) && (b.equals(curve.b)) && (Arrays.equals(seed, curve.seed))) { return true; } } return false;
public java.math.BigInteger	getA() Returns the first coefficient a of the elliptic curve. return the first coefficient a. return a;
public java.math.BigInteger	getB() Returns the second coefficient b of the elliptic curve. return the second coefficient b. return b;
public java.security.spec.ECField	getField() Returns the finite field field that this elliptic curve is over. return the field field that this curve is over. return field;
public byte[]	getSeed() Returns the seeding bytes seed used during curve generation. May be null if not specified. return the seeding bytes seed. A new array is returned each time this method is called. if (seed == null) return null; else return (byte[]) seed.clone();
public int	hashCode() Returns a hash code value for this elliptic curve. return a hash code value. return (field.hashCode() << 6 + (a.hashCode() << 4) + (b.hashCode() << 2) + (seed==null? 0:seed.length));