NAME¶
EC_GFp_simple_method, EC_GFp_mont_method, EC_GFp_nist_method,
EC_GFp_nistp224_method, EC_GFp_nistp256_method, EC_GFp_nistp521_method,
EC_GF2m_simple_method, EC_METHOD_get_field_type - Functions for obtaining
EC_METHOD objects.
SYNOPSIS¶
#include <openssl/ec.h>
const EC_METHOD *EC_GFp_simple_method(void);
const EC_METHOD *EC_GFp_mont_method(void);
const EC_METHOD *EC_GFp_nist_method(void);
const EC_METHOD *EC_GFp_nistp224_method(void);
const EC_METHOD *EC_GFp_nistp256_method(void);
const EC_METHOD *EC_GFp_nistp521_method(void);
const EC_METHOD *EC_GF2m_simple_method(void);
int EC_METHOD_get_field_type(const EC_METHOD *meth);
DESCRIPTION¶
The Elliptic Curve library provides a number of different implementations
through a single common interface. When constructing a curve using
EC_GROUP_new (see
EC_GROUP_new(3)) an implementation method must be
provided. The functions described here all return a const pointer to an
EC_METHOD structure that can be passed to EC_GROUP_NEW. It is important
that the correct implementation type for the form of curve selected is used.
For F2^m curves there is only one implementation choice, i.e.
EC_GF2_simple_method.
For Fp curves the lowest common denominator implementation is the
EC_GFp_simple_method implementation. All other implementations are based on
this one. EC_GFp_mont_method builds on EC_GFp_simple_method but adds the use
of montgomery multiplication (see
BN_mod_mul_montgomery(3)).
EC_GFp_nist_method offers an implementation optimised for use with NIST
recommended curves (NIST curves are available through
EC_GROUP_new_by_curve_name as described in
EC_GROUP_new(3)).
The functions EC_GFp_nistp224_method, EC_GFp_nistp256_method and
EC_GFp_nistp521_method offer 64 bit optimised implementations for the NIST
P224, P256 and P521 curves respectively. Note, however, that these
implementations are not available on all platforms.
EC_METHOD_get_field_type identifies what type of field the EC_METHOD structure
supports, which will be either F2^m or Fp. If the field type is Fp then the
value
NID_X9_62_prime_field is returned. If the field type is F2^m then
the value
NID_X9_62_characteristic_two_field is returned. These values
are defined in the obj_mac.h header file.
RETURN VALUES¶
All EC_GFp* functions and EC_GF2m_simple_method always return a const pointer to
an EC_METHOD structure.
EC_METHOD_get_field_type returns an integer that identifies the type of field
the EC_METHOD structure supports.
SEE ALSO¶
crypto(3),
ec(3),
EC_GROUP_new(3),
EC_GROUP_copy(3),
EC_POINT_new(3),
EC_POINT_add(3),
EC_KEY_new(3),
d2i_ECPKParameters(3),
BN_mod_mul_montgomery(3)