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EC_GFp_simple_method, EC_GFp_mont_method, EC_METHOD_get_field_typeobtain EC_METHOD objects

#include <openssl/ec.h>

const EC_METHOD *

const EC_METHOD *

EC_METHOD_get_field_type(const EC_METHOD *meth);

The elliptic curve library provides a number of different implementations through a single common interface. Each implementation is optimised for different scenarios. An implementation is represented by an EC_METHOD structure.

When constructing a curve using EC_GROUP_new(3), an implementation method must be provided. The functions described here all return a const pointer to an structure that can be passed to EC_GROUP_new(3). It is important that the correct implementation type for the form of curve selected is used.

For Fp curves the lowest common denominator implementation is the () implementation. All other implementations are based on this one. () adds the use of Montgomery multiplication (see BN_mod_mul_montgomery(3)).

() identifies what type of field the EC_METHOD structure supports. 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 <openssl/objects.h> header file.

All EC_GFp*() functions 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.

BN_mod_mul_montgomery(3), d2i_ECPKParameters(3), EC_GROUP_copy(3), EC_GROUP_new(3), EC_KEY_new(3), EC_POINT_add(3), EC_POINT_new(3)

EC_GFp_simple_method() and EC_GFp_mont_method() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

EC_METHOD_get_field_type() first appeared in OpenSSL 0.9.8 and has been available since OpenBSD 4.5.

April 27, 2023 OpenBSD-current