1=pod 2 3=head1 NAME 4 5EC_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 6 7=head1 SYNOPSIS 8 9 #include <openssl/ec.h> 10 11 const EC_METHOD *EC_GFp_simple_method(void); 12 const EC_METHOD *EC_GFp_mont_method(void); 13 const EC_METHOD *EC_GFp_nist_method(void); 14 const EC_METHOD *EC_GFp_nistp224_method(void); 15 const EC_METHOD *EC_GFp_nistp256_method(void); 16 const EC_METHOD *EC_GFp_nistp521_method(void); 17 18 const EC_METHOD *EC_GF2m_simple_method(void); 19 20 int EC_METHOD_get_field_type(const EC_METHOD *meth); 21 22=head1 DESCRIPTION 23 24The Elliptic Curve library provides a number of different implementations through a single common interface. 25When constructing a curve using EC_GROUP_new (see L<EC_GROUP_new(3)>) an 26implementation method must be provided. The functions described here all return a const pointer to an 27B<EC_METHOD> structure that can be passed to EC_GROUP_NEW. It is important that the correct implementation 28type for the form of curve selected is used. 29 30For F2^m curves there is only one implementation choice, i.e. EC_GF2_simple_method. 31 32For Fp curves the lowest common denominator implementation is the EC_GFp_simple_method implementation. All 33other implementations are based on this one. EC_GFp_mont_method builds on EC_GFp_simple_method but adds the 34use of montgomery multiplication (see L<BN_mod_mul_montgomery(3)>). EC_GFp_nist_method 35offers an implementation optimised for use with NIST recommended curves (NIST curves are available through 36EC_GROUP_new_by_curve_name as described in L<EC_GROUP_new(3)>). 37 38The functions EC_GFp_nistp224_method, EC_GFp_nistp256_method and EC_GFp_nistp521_method offer 64 bit 39optimised implementations for the NIST P224, P256 and P521 curves respectively. Note, however, that these 40implementations are not available on all platforms. 41 42EC_METHOD_get_field_type identifies what type of field the EC_METHOD structure supports, which will be either 43F2^m or Fp. If the field type is Fp then the value B<NID_X9_62_prime_field> is returned. If the field type is 44F2^m then the value B<NID_X9_62_characteristic_two_field> is returned. These values are defined in the 45obj_mac.h header file. 46 47=head1 RETURN VALUES 48 49All EC_GFp* functions and EC_GF2m_simple_method always return a const pointer to an EC_METHOD structure. 50 51EC_METHOD_get_field_type returns an integer that identifies the type of field the EC_METHOD structure supports. 52 53=head1 SEE ALSO 54 55L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>, 56L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>, 57L<d2i_ECPKParameters(3)>, 58L<BN_mod_mul_montgomery(3)> 59 60=head1 COPYRIGHT 61 62Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved. 63 64Licensed under the OpenSSL license (the "License"). You may not use 65this file except in compliance with the License. You can obtain a copy 66in the file LICENSE in the source distribution or at 67L<https://www.openssl.org/source/license.html>. 68 69=cut 70