java.security.spec

Class ECFieldF2m

Table des matières
  • All Implemented Interfaces:
    ECField

    public class ECFieldF2m
extends Object
implements ECField
    This immutable class defines an elliptic curve (EC) characteristic 2 finite field.
    Since:
    1.5
    See Also:
    ECField

    • Constructor Summary

      Constructors 
      Constructor and Description
      ECFieldF2m(int m)
      Creates an elliptic curve characteristic 2 finite field which has 2^m elements with normal basis.
      ECFieldF2m(int m, BigInteger rp)
      Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis.
      ECFieldF2m(int m, int[] ks)
      Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis.

        

    • Method Summary

      Methods 
      Modifier and Type Method and Description
      boolean equals(Object obj)
      Compares this finite field for equality with the specified object.
      int getFieldSize()
      Returns the field size in bits which is m for this characteristic 2 finite field.
      int getM()
      Returns the value m of this characteristic 2 finite field.
      int[] getMidTermsOfReductionPolynomial()
      Returns an integer array which contains the order of the middle term(s) of the reduction polynomial for polynomial basis or null for normal basis.
      BigInteger getReductionPolynomial()
      Returns a BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction polynomial for polynomial basis or null for normal basis.
      int hashCode()
      Returns a hash code value for this characteristic 2 finite field.

        

    • Constructor Detail

      • ECFieldF2m

        public ECFieldF2m(int m)
        Creates an elliptic curve characteristic 2 finite field which has 2^m elements with normal basis.
        Parameters:
        m - with 2^m being the number of elements.
        Throws:
        IllegalArgumentException - if m is not positive.

      • ECFieldF2m

        public ECFieldF2m(int m,
          BigInteger rp)
        Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis. The reduction polynomial for this field is based on rp whose i-th bit correspondes to the i-th coefficient of the reduction polynomial.

        Note: A valid reduction polynomial is either a trinomial (X^m + X^k + 1 with m > k >= 1) or a pentanomial (X^m + X^k3 + X^k2 + X^k1 + 1 with m > k3 > k2 > k1 >= 1).

        Parameters:
        m - with 2^m being the number of elements.
        rp - the BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction polynomial.
        Throws:
        NullPointerException - if rp is null.
        IllegalArgumentException - if m is not positive, or rp does not represent a valid reduction polynomial.

      • ECFieldF2m

        public ECFieldF2m(int m,
          int[] ks)
        Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis. The reduction polynomial for this field is based on ks whose content contains the order of the middle term(s) of the reduction polynomial. Note: A valid reduction polynomial is either a trinomial (X^m + X^k + 1 with m > k >= 1) or a pentanomial (X^m + X^k3 + X^k2 + X^k1 + 1 with m > k3 > k2 > k1 >= 1), so ks should have length 1 or 3.
        Parameters:
        m - with 2^m being the number of elements.
        ks - the order of the middle term(s) of the reduction polynomial. Contents of this array are copied to protect against subsequent modification.
        Throws:
        NullPointerException - if ks is null.
        IllegalArgumentException - ifm is not positive, or the length of ks is neither 1 nor 3, or values in ks are not between m-1 and 1 (inclusive) and in descending order.

    • Method Detail

      • getFieldSize

        public int getFieldSize()
        Returns the field size in bits which is m for this characteristic 2 finite field.
        Specified by:
        getFieldSize in interface ECField
        Returns:
        the field size in bits.

      • getM

        public int getM()
        Returns the value m of this characteristic 2 finite field.
        Returns:
        m with 2^m being the number of elements.

      • getReductionPolynomial

        public BigInteger getReductionPolynomial()
        Returns a BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction polynomial for polynomial basis or null for normal basis.
        Returns:
        a BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction polynomial for polynomial basis or null for normal basis.

      • getMidTermsOfReductionPolynomial

        public int[] getMidTermsOfReductionPolynomial()
        Returns an integer array which contains the order of the middle term(s) of the reduction polynomial for polynomial basis or null for normal basis.
        Returns:
        an integer array which contains the order of the middle term(s) of the reduction polynomial for polynomial basis or null for normal basis. A new array is returned each time this method is called.

      • equals

        public boolean equals(Object obj)
        Compares this finite field 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 ECFieldF2m and both m and the reduction polynomial match, false otherwise.
        See Also:
        Object.hashCode(), HashMap

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Document créé le 31/08/2006, dernière modification le 04/03/2020
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