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(7), 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)

COPYRIGHT

       Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.