de.flexiprovider.common.math.finitefields
Class GFPElement

java.lang.Object
  |
  +--de.flexiprovider.common.math.finitefields.GFPElement

All Implemented Interfaces:

GFElement

public class GFPElement

extends java.lang.Object

implements GFElement

This class implements an element of the finite field GF(p), where p is a large prime.

Author:

Birgit Henhapl, Martin Döring

See Also:

GF2nElement, GFPElement

Constructor Summary

GFPElement(byte[] encValue, FlexiBigInt p)
Create a new GFPElement from the given encoded value and field order.

GFPElement(FlexiBigInt value, FlexiBigInt p)
Create a new GFPElement from the given value and field order.

GFPElement(GFPElement other)
Copy constructor.

Method Summary

GFElement	add(GFElement addend) Compute the sum of this element and addend.
void	addToThis(GFElement addend) Compute this + addend (overwrite this).
java.lang.Object	clone()
boolean	equals(java.lang.Object other) Compare this element with another object.
int	hashCode()
GFElement	invert() Compute the multiplicative inverse of this element.
boolean	isOne() Checks whether this element is one.
boolean	isZero() Checks whether this element is zero.
GFElement	multiply(GFElement factor) Compute the product of this element and factor.
void	multiplyThisBy(GFElement factor) Compute this * factor (overwrite this).
GFPElement	negate() Compute the additive inverse of this element.
static GFPElement	ONE(FlexiBigInt p) Create the one element.
GFElement	subtract(GFElement minuend) Compute the difference of this element and minuend.
void	subtractFromThis(GFElement minuend) Compute the difference of this element and minuend, overwriting this element.
byte[]	toByteArray() Returns this element as byte array.
FlexiBigInt	toFlexiBigInt() Returns this element as FlexiBigInt.
java.lang.String	toString() Return a String representation of this element.
java.lang.String	toString(int radix) Return a String representation of this element.
static GFPElement	ZERO(FlexiBigInt p) Create the zero element.

Methods inherited from class java.lang.Object

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

Constructor Detail

GFPElement

public GFPElement(FlexiBigInt value,
                  FlexiBigInt p)

Create a new GFPElement from the given value and field order.

Parameters:

value - the value

p - the order of the field

GFPElement

public GFPElement(byte[] encValue,
                  FlexiBigInt p)

Create a new GFPElement from the given encoded value and field order.

Parameters:

encValue - the encoded value

p - the order of the field

GFPElement

public GFPElement(GFPElement other)

Copy constructor.

Parameters:

other - another GFPElement

Method Detail

clone

public java.lang.Object clone()

Specified by:

clone in interface GFElement

Overrides:

clone in class java.lang.Object

Returns:

a copy of this GFPElement

ZERO

public static GFPElement ZERO(FlexiBigInt p)

Create the zero element.

Parameters:

p - the modulus

Returns:

the zero element in GF(p)

ONE

public static GFPElement ONE(FlexiBigInt p)

Create the one element.

Parameters:

p - the modulus

Returns:

the one element in GF(p)

isZero

public boolean isZero()

Checks whether this element is zero.

Specified by:

isZero in interface GFElement

Returns:

true if this is the zero element

isOne

public boolean isOne()

Checks whether this element is one.

Specified by:

isOne in interface GFElement

Returns:

true if this is the one element

equals

public boolean equals(java.lang.Object other)

Compare this element with another object.

Specified by:

equals in interface GFElement

Overrides:

equals in class java.lang.Object

Parameters:

other - the other object

Returns:

true if the two objects are equal, false otherwise

hashCode

public int hashCode()

Specified by:

hashCode in interface GFElement

Overrides:

hashCode in class java.lang.Object

Returns:

the hash code of this element

add

public GFElement add(GFElement addend)
              throws DifferentFieldsException

Compute the sum of this element and addend.

Specified by:

add in interface GFElement

Parameters:

addend - the addend

Returns:

this + other (newly created)

Throws:

DifferentFieldsException - if the elements are of different fields.

addToThis

public void addToThis(GFElement addend)
               throws DifferentFieldsException

Compute this + addend (overwrite this).

Specified by:

addToThis in interface GFElement

Parameters:

addend - the addend

Throws:

DifferentFieldsException - if the elements are of different fields.

subtract

public GFElement subtract(GFElement minuend)
                   throws DifferentFieldsException

Compute the difference of this element and minuend.

Specified by:

subtract in interface GFElement

Parameters:

minuend - the minuend

Returns:

this - minuend (newly created)

Throws:

DifferentFieldsException - if the elements are of different fields.

subtractFromThis

public void subtractFromThis(GFElement minuend)
                      throws DifferentFieldsException

Compute the difference of this element and minuend, overwriting this element.

Specified by:

subtractFromThis in interface GFElement

Parameters:

minuend - the minuend

Throws:

DifferentFieldsException - if the elements are of different fields.

negate

public GFPElement negate()

Compute the additive inverse of this element.

Returns:

-this (newly created)

multiply

public GFElement multiply(GFElement factor)
                   throws DifferentFieldsException

Compute the product of this element and factor.

Specified by:

multiply in interface GFElement

Parameters:

factor - the factor

Returns:

this * factor (newly created)

Throws:

DifferentFieldsException - if the elements are of different fields.

multiplyThisBy

public void multiplyThisBy(GFElement factor)
                    throws DifferentFieldsException

Compute this * factor (overwrite this).

Specified by:

multiplyThisBy in interface GFElement

Parameters:

factor - the factor

Throws:

DifferentFieldsException - if the elements are of different fields.

invert

public GFElement invert()
                 throws java.lang.ArithmeticException

Compute the multiplicative inverse of this element.

Specified by:

invert in interface GFElement

Returns:

this^-1 (newly created)

Throws:

java.lang.ArithmeticException - if this is the zero element.

toByteArray

public byte[] toByteArray()

Description copied from interface: GFElement

Returns this element as byte array. The conversion is P1363-conform.

Specified by:

toByteArray in interface GFElement

Returns:

this element as byte array

toFlexiBigInt

public FlexiBigInt toFlexiBigInt()

Description copied from interface: GFElement

Returns this element as FlexiBigInt. The conversion is P1363-conform.

Specified by:

toFlexiBigInt in interface GFElement

Returns:

this element as FlexiBigInt

toString

public java.lang.String toString()

Description copied from interface: GFElement

Return a String representation of this element.

Specified by:

toString in interface GFElement

Overrides:

toString in class java.lang.Object

Returns:

a human readable form of this element

toString

public java.lang.String toString(int radix)

Description copied from interface: GFElement

Return a String representation of this element. radix specifies the radix of the String representation.

Specified by:

toString in interface GFElement

Following copied from interface: de.flexiprovider.common.math.finitefields.GFElement

Parameters:

radix - specifies the radix of the String representation

Returns:

String representation of this element with the specified radix