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EC_GFP_SIMPLE_METHOD(3) Library Functions Manual EC_GFP_SIMPLE_METHOD(3)

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_typeobtain EC_METHOD objects

#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);

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 F2^m curves there is only one implementation choice, ().

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)). () offers an implementation optimised for use with NIST recommended curves. NIST curves are available through EC_GROUP_new_by_curve_name(3).

The functions (), (), and () 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.

() 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 <openssl/objects.h> header file.

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.

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_GFp_nist_method(), EC_GF2m_simple_method(), and EC_METHOD_get_field_type() first appeared in OpenSSL 0.9.8 and have been available since OpenBSD 4.5.

EC_GFp_nistp224_method(), EC_GFp_nistp256_method(), and EC_GFp_nistp521_method() first appeared in OpenSSL 1.0.1 and have been available since OpenBSD 5.3.

July 2, 2022 OpenBSD-current