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 B<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)|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)|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)|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(3)|crypto(3)>, L<ec(3)|ec(3)>, L<EC_GROUP_new(3)|EC_GROUP_new(3)>, L<EC_GROUP_copy(3)|EC_GROUP_copy(3)>, 56L<EC_POINT_new(3)|EC_POINT_new(3)>, L<EC_POINT_add(3)|EC_POINT_add(3)>, L<EC_KEY_new(3)|EC_KEY_new(3)>, 57L<d2i_ECPKParameters(3)|d2i_ECPKParameters(3)>, 58L<BN_mod_mul_montgomery(3)|BN_mod_mul_montgomery(3)> 59 60=cut 61