Class EllipticCurve

java.lang.Object

java.security.spec.EllipticCurve

public class EllipticCurve
extends Object

This immutable class holds the necessary values needed to represent an elliptic curve.

Since:

1.5

See Also:

• ECField
• ECFieldFp
• ECFieldF2m

Constructor Summary

Constructors

Constructor	Description
EllipticCurve(ECField field, BigInteger a, BigInteger b)	Creates an elliptic curve with the specified elliptic field field and the coefficients a and b.
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.

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object obj)	Compares this elliptic curve for equality with the specified object.
BigInteger	getA()	Returns the first coefficient a of the elliptic curve.
BigInteger	getB()	Returns the second coefficient b of the elliptic curve.
ECField	getField()	Returns the finite field field that this elliptic curve is over.
byte[]	getSeed()	Returns the seeding bytes seed used during curve generation.
int	hashCode()	Returns a hash code value for this elliptic curve.

Methods declared in class Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Details

EllipticCurve

public EllipticCurve(ECField field,
 BigInteger a,
 BigInteger b)

Creates an elliptic curve with the specified elliptic field field and the coefficients a and b.

Parameters:

field - the finite field that this elliptic curve is over.

a - the first coefficient of this elliptic curve.

b - the second coefficient of this elliptic curve.

Throws:

NullPointerException - if field, a, or b is null.

IllegalArgumentException - if a or b is not null and not in field.

EllipticCurve

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.

Parameters:

field - the finite field that this elliptic curve is over.

a - the first coefficient of this elliptic curve.

b - the second coefficient of this elliptic curve.

seed - the bytes used during curve generation for later validation. Contents of this array are copied to protect against subsequent modification.

Throws:

NullPointerException - if field, a, or b is null.

IllegalArgumentException - if a or b is not null and not in field.

Method Details

getField

public ECField getField()

Returns the finite field field that this elliptic curve is over.

Returns:

the field field that this curve is over.

getA

public BigInteger getA()

Returns the first coefficient a of the elliptic curve.

Returns:

the first coefficient a.

getB

public BigInteger getB()

Returns the second coefficient b of the elliptic curve.

Returns:

the second coefficient b.

getSeed

public byte[] getSeed()

Returns the seeding bytes seed used during curve generation. May be null if not specified.

Returns:

the seeding bytes seed. A new array is returned each time this method is called.

equals

public boolean equals(Object obj)

Compares this elliptic curve for equality with the specified object.

Overrides:

equals in class Object

Parameters:

obj - the object to be compared.

Returns:

true if obj is an instance of EllipticCurve and the field, A, and B match, false otherwise.

See Also:

• Object.hashCode()
• HashMap

hashCode

public int hashCode()

Returns a hash code value for this elliptic curve.

Overrides:

hashCode in class Object

Returns:

a hash code value computed from the hash codes of the field, A, and B, as follows:

    (field.hashCode() << 6) + (a.hashCode() << 4) + (b.hashCode() << 2)

See Also:

• Object.equals(java.lang.Object)
• System.identityHashCode(Object)