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 ism
for this characteristic 2 finite field.int
getM()
Returns the valuem
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 ith bit corresponds to the ith 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 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
 ifm
is not positive.

ECFieldF2m
Creates an elliptic curve characteristic 2 finite field which has 2^m
elements with polynomial basis. The reduction polynomial for this field is based onrp
whose ith bit corresponds to the ith coefficient of the reduction polynomial.Note: A valid reduction polynomial is either a trinomial (X^
m
+ X^k
+ 1 withm
>k
>= 1) or a pentanomial (X^m
+ X^k3
+ X^k2
+ X^k1
+ 1 withm
>k3
>k2
>k1
>= 1). Parameters:
m
 with 2^m
being the number of elements.rp
 the BigInteger whose ith bit corresponds to the ith coefficient of the reduction polynomial. Throws:
NullPointerException
 ifrp
is null.IllegalArgumentException
 ifm
is not positive, orrp
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 onks
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 withm
>k
>= 1) or a pentanomial (X^m
+ X^k3
+ X^k2
+ X^k1
+ 1 withm
>k3
>k2
>k1
>= 1), soks
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
 ifks
is null.IllegalArgumentException
 ifm
is not positive, or the length ofks
is neither 1 nor 3, or values inks
are not betweenm
1 and 1 (inclusive) and in descending order.


Method Details

getFieldSize
public int getFieldSize()Returns the field size in bits which ism
for this characteristic 2 finite field. Specified by:
getFieldSize
in interfaceECField
 Returns:
 the field size in bits.

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

getReductionPolynomial
Returns a BigInteger whose ith bit corresponds to the ith coefficient of the reduction polynomial for polynomial basis or null for normal basis. Returns:
 a BigInteger whose ith bit corresponds to the ith 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
Compares this finite field for equality with the specified object. Overrides:
equals
in classObject
 Parameters:
obj
 the object to be compared. Returns:
 true if
obj
is an instance of ECFieldF2m and bothm
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 classObject
 Returns:
 a hash code value.
 See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
