NAME
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_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);
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);
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 F2^m curves there is only one
implementation choice,
EC_GF2_simple_method().
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_GFp_nist_method()
offers an implementation optimised for use with NIST recommended curves.
NIST curves are available through
EC_GROUP_new_by_curve_name(3).
The functions
EC_GFp_nistp224_method(),
EC_GFp_nistp256_method(),
and
EC_GFp_nistp521_method()
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.
EC_METHOD_get_field_type()
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/obj_mac.h> header
file.
RETURN VALUES
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.
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_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.