Module java.base
Package java.security.spec

Class ECFieldF2m

java.lang.Object
java.security.spec.ECFieldF2m
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 Description
    ECFieldF2m​(int m)
    Creates an elliptic curve characteristic 2 finite field which has 2^m elements with normal basis.
    ECFieldF2m​(int m, int[] ks)
    Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis.
    ECFieldF2m​(int m, BigInteger rp)
    Creates an elliptic curve characteristic 2 finite field which has 2^m elements with polynomial basis.

  • Method Summary

    Modifier and Type Method 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.

    Methods declared in class java.lang.Object

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

  • Constructor Details

    • 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 corresponds 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 Details

    • 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

    • hashCode

      public int hashCode()
      Returns a hash code value for this characteristic 2 finite field.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value.
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)