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ECFieldF2m

public class ECFieldF2m
extends Object implements ECField

java.lang.Object
   ↳ java.security.spec.ECFieldF2m


This immutable class defines an elliptic curve (EC) characteristic 2 finite field.

See also:

Summary

Public constructors

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.

Public methods

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.

Inherited methods

From class java.lang.Object
From interface java.security.spec.ECField

Public constructors

ECFieldF2m

Added in API level 1
ECFieldF2m (int m)

Creates an elliptic curve characteristic 2 finite field which has 2^m elements with normal basis.

Parameters
m int: with 2^m being the number of elements.
Throws
IllegalArgumentException if m is not positive.

ECFieldF2m

Added in API level 1
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 int: with 2^m being the number of elements.
rp BigInteger: 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

Added in API level 1
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 int: with 2^m being the number of elements.
ks int: 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.

Public methods

equals

Added in API level 1
boolean equals (Object obj)

Compares this finite field for equality with the specified object.

Parameters
obj Object: the object to be compared.
Returns
boolean true if obj is an instance of ECFieldF2m and both m and the reduction polynomial match, false otherwise.

getFieldSize

Added in API level 1
int getFieldSize ()

Returns the field size in bits which is m for this characteristic 2 finite field.

Returns
int the field size in bits.

getM

Added in API level 1
int getM ()

Returns the value m of this characteristic 2 finite field.

Returns
int m with 2^m being the number of elements.

getMidTermsOfReductionPolynomial

Added in API level 1
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
int[] 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.

getReductionPolynomial

Added in API level 1
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
BigInteger a BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction polynomial for polynomial basis or null for normal basis.

hashCode

Added in API level 1
int hashCode ()

Returns a hash code value for this characteristic 2 finite field.

Returns
int a hash code value.
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