Package org.bouncycastle.pqc.crypto.rainbow.util

Class 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.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int MASK  

    • Constructor Summary

      Constructors 
      Constructor Description
      GF2Field()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      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

    • 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