Java™ Platform
Standard Ed. 6

java.security.spec
Class ECFieldF2m

java.lang.Object
  extended by 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
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
 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 inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

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(), Hashtable

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), Hashtable

Java™ Platform
Standard Ed. 6

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