iaik.security.ec.math.curve

Class ECPoint

java.lang.Object

iaik.security.ec.math.curve.ECPoint

All Implemented Interfaces:

Cloneable

public final class ECPoint
extends Object
implements Cloneable

This class is used to represent points on arbitrary elliptic curves. It provides the most important methods for point arithmetic.

Note that (almost) all methods in this class work in-place. So, there is no guarantee that values input to methods in this class will not be overridden. In case of doubt and if values need to be reused, always clone the value, before inputting it to a method.

Author:

Christian Hanser

See Also:

EllipticCurve, Coordinate

Method Summary

Modifier and Type	Method and Description
ECPoint	addPoint(ECPoint b) Computes this += b.
static void	allFunctionsInPlace(boolean value) Switch to set if all functions should work in-place.
ECPoint	clone()
ECPoint	doublePoint() Computes this *= 2.
byte[]	encodePoint() Encodes this point, i.e.
byte[]	encodePoint(PointEncoders encoder) Encodes this point, i.e.
boolean	equals(Object obj) This method compares two different ECPoint instances.
Coordinate	getCoordinate() Returns the coordinates of this point.
EllipticCurve	getCurve() Returns the curve on which this point is defined.
int	hashCode()
boolean	isNeutralPoint() Returns true, iff this is the neutral element.
boolean	isScaled() Checks whether this point is scaled, i.e.
ECPoint	mixedAddPoint(ECPoint b) Computes this += b, where b is either scaled or given in affine coordinates.
ECPoint	mixedSubtractPoint(ECPoint b) Computes this -= b, where b is either scaled or given in affine coordinates.
ECPoint	multiplyPoint(BigInteger k) Computes this *= k.
ECPoint	negatePoint() Negates this point, i.e.
ECPoint	scalePoint() Scales this, i.e.
ECPoint	setNeutralPoint() Sets this to the neutral element.
ECPoint	subtractPoint(ECPoint b) Computes this -= b.
ECPoint	toJDKECPoint() Converts this point to a point of the class ECPoint.
String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

getCurve

public EllipticCurve getCurve()

Returns the curve on which this point is defined.

Returns:

the curve

addPoint

public ECPoint addPoint(ECPoint b)

Computes this += b.

Parameters:

b - the addend

Returns:

this holding the sum

mixedAddPoint

public ECPoint mixedAddPoint(ECPoint b)

Computes this += b, where b is either scaled or given in affine coordinates. This function is only in-place if workInPlace is set to true.

Parameters:

b - the addend

Returns:

this holding the sum

subtractPoint

public ECPoint subtractPoint(ECPoint b)

Computes this -= b.

Parameters:

b - the subtrahend

Returns:

this holding the difference

negatePoint

public ECPoint negatePoint()

Negates this point, i.e. sets this = -this.

Returns:

the negative of this

mixedSubtractPoint

public ECPoint mixedSubtractPoint(ECPoint b)

Computes this -= b, where b is either scaled or given in affine coordinates.

Parameters:

b - the subtrahend

Returns:

the difference

doublePoint

public ECPoint doublePoint()

Computes this *= 2.

Returns:

the double of this

multiplyPoint

public ECPoint multiplyPoint(BigInteger k)

Computes this *= k. It is assumed that k is a scalar modulo the order of the curve group. This function is only in-place if workInPlace is set to true.

Parameters:

k - the scalar

Returns:

the multiple of this

scalePoint

public ECPoint scalePoint()

Scales this, i.e. returns the according point with Z=1.

Returns:

the scaled version of this

isScaled

public boolean isScaled()

Checks whether this point is scaled, i.e. whether it is either affine or has z-coordinate 1.

Returns:

true, iff this is scaled.

getCoordinate

public Coordinate getCoordinate()

Returns the coordinates of this point. Call scalePoint() before obtaining the coordinates.

Returns:

a Coordinate object holding the coordinates

isNeutralPoint

public boolean isNeutralPoint()

Returns true, iff this is the neutral element.

Returns:

true, iff this is the neutral element

setNeutralPoint

public ECPoint setNeutralPoint()

Sets this to the neutral element.

Returns:

this instance

toJDKECPoint

public ECPoint toJDKECPoint()

Converts this point to a point of the class ECPoint.

Returns:

a JDK ECPoint instance

encodePoint

public byte[] encodePoint(PointEncoders encoder)

Encodes this point, i.e. converts it to a byte[]. The user can choose between point compression (if the IAIK ECCelerate™ Addon is available) and non-compressed encoding.

Parameters:

encoder - the point encoding algorithm to be used

Returns:

a byte[] representing the encoded point

encodePoint

public byte[] encodePoint()

Encodes this point, i.e. converts it to a byte[] using the default point encoding mechanism.

Returns:

a byte[] representing the encoded point

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

This method compares two different ECPoint instances.

Overrides:

equals in class Object

Parameters:

obj - another ECPoint instance

Returns:

true iff both points are the same

clone

public ECPoint clone()

Overrides:

clone in class Object

toString

public String toString()

Overrides:

toString in class Object

allFunctionsInPlace

public static void allFunctionsInPlace(boolean value)

Switch to set if all functions should work in-place. If set to true, all functions work in-place. If set to false, behaviour from previous versions will be used. (Mixed behaviour, but most functions are in-place). Note: Not synchronized!

Parameters:

value - if set to true, all Functions work in-place. Default value is false