de.flexiprovider.pqc.rainbow.util
Class GF2Field

java.lang.Object
  |
  +--de.flexiprovider.pqc.rainbow.util.GF2Field

public class GF2Field

extends java.lang.Object

This class provides the basic operations like addition, multiplication and finding the multiplicative inverse of an element in GF2^8. The operations are implemented using the irreducible polynomial 1+x^2+x^3+x^6+x^8 ( 1 0100 1101 = 0x14d ) This class makes use of lookup tables(exps and logs) for implementing the operations in order to increase the efficiency of Rainbow.

Author:

Patrick Neugebauer, Marius Senftleben, Tsvetoslava Vateva

Field Summary

(package private) static short[]	exps
(package private) static short[]	logs
static int	MASK

Constructor Summary

GF2Field()

Method Summary

static short	addElem(short x, short y) This function calculates the sum of two elements as an operation in GF2^8
static short	getExp(short x) This function returns the values of exps-lookup table which correspond to the input
static short	getLog(short x) This function returns the values of logs-lookup table which correspond to the input
static short	invElem(short x) This function computes the multiplicative inverse of a given element in GF2^8 The 0 has no multiplicative inverse and in this case 0 is returned.
static short	multElem(short x, short y) This function multiplies two elements in GF2^8.

Methods inherited from class java.lang.Object

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

Field Detail

MASK

public static final int MASK

exps

static final short[] exps

logs

static final short[] logs

Constructor Detail

GF2Field

public GF2Field()

Method Detail

addElem

public static short addElem(short x,
                            short y)

This function calculates the sum of two elements as an operation in GF2^8

Parameters:

x - the first element that is to be added

y - the second element that should be add

Returns:

the sum of the two elements x and y in GF2^8

invElem

public static short invElem(short x)

This function computes the multiplicative inverse of a given element in GF2^8 The 0 has no multiplicative inverse and in this case 0 is returned.

Parameters:

x - the element which multiplicative inverse is to be computed

Returns:

the multiplicative inverse of the given element, in case it exists or 0, otherwise

multElem

public static short multElem(short x,
                             short y)

This function multiplies two elements in GF2^8. If one of the two elements is 0, 0 is returned.

Parameters:

x - the first element to be multiplied.

y - the second element to be multiplied.

Returns:

the product of the two input elements in GF2^8.

getExp

public static short getExp(short x)

This function returns the values of exps-lookup table which correspond to the input

Parameters:

x - the index in the lookup table exps

Returns:

exps-value, corresponding to the input

getLog

public static short getLog(short x)

This function returns the values of logs-lookup table which correspond to the input

Parameters:

x - the index in the lookup table logs

Returns:

logs-value, corresponding to the input