NAME

EC_GFp_simple_method, EC_GFp_mont_method, EC_METHOD_get_field_type — obtain EC_METHOD objects

SYNOPSIS

#include <openssl/ec.h>

const EC_METHOD *
EC_GFp_simple_method(void);

const EC_METHOD *
EC_GFp_mont_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. 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 EC_METHOD 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 EC_GFp_simple_method() implementation. All other implementations are based on this one. EC_GFp_mont_method() adds the use of Montgomery multiplication (see BN_mod_mul_montgomery(3)).

EC_METHOD_get_field_type() 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.

RETURN VALUES

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.

SEE ALSO

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)

HISTORY

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.