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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 Apache License 2.0 (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>.