.\" $OpenBSD: EC_GFp_simple_method.3,v 1.9 2018/03/23 05:48:56 schwarze Exp $ .\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100 .\" .\" This file was written by Matt Caswell . .\" Copyright (c) 2013 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: March 23 2018 $ .Dt EC_GFP_SIMPLE_METHOD 3 .Os .Sh NAME .Nm EC_GFp_simple_method , .Nm EC_GFp_mont_method , .Nm EC_GFp_nist_method , .Nm EC_GFp_nistp224_method , .Nm EC_GFp_nistp256_method , .Nm EC_GFp_nistp521_method , .Nm EC_GF2m_simple_method , .Nm EC_METHOD_get_field_type .Nd obtain EC_METHOD objects .Sh SYNOPSIS .In openssl/ec.h .Ft const EC_METHOD * .Fn EC_GFp_simple_method void .Ft const EC_METHOD * .Fn EC_GFp_mont_method void .Ft const EC_METHOD * .Fn EC_GFp_nist_method void .Ft const EC_METHOD * .Fn EC_GFp_nistp224_method void .Ft const EC_METHOD * .Fn EC_GFp_nistp256_method void .Ft const EC_METHOD * .Fn EC_GFp_nistp521_method void .Ft const EC_METHOD * .Fn EC_GF2m_simple_method void .Ft int .Fo EC_METHOD_get_field_type .Fa "const EC_METHOD *meth" .Fc .Sh 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 .Vt EC_METHOD structure. .Pp When constructing a curve using .Xr EC_GROUP_new 3 , an implementation method must be provided. The functions described here all return a const pointer to an .Sy EC_METHOD structure that can be passed to .Xr EC_GROUP_new 3 . It is important that the correct implementation type for the form of curve selected is used. .Pp For F2^m curves there is only one implementation choice, .Fn EC_GF2_simple_method . .Pp For Fp curves the lowest common denominator implementation is the .Fn EC_GFp_simple_method implementation. All other implementations are based on this one. .Fn EC_GFp_mont_method adds the use of Montgomery multiplication (see .Xr BN_mod_mul_montgomery 3 ) . .Fn EC_GFp_nist_method offers an implementation optimised for use with NIST recommended curves. NIST curves are available through .Xr EC_GROUP_new_by_curve_name 3 . .Pp The functions .Fn EC_GFp_nistp224_method , .Fn EC_GFp_nistp256_method , and .Fn 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. .Pp .Fn EC_METHOD_get_field_type identifies what type of field the .Vt EC_METHOD structure supports, which will be either F2^m or Fp. If the field type is Fp, then the value .Dv NID_X9_62_prime_field is returned. If the field type is F2^m, then the value .Dv NID_X9_62_characteristic_two_field is returned. These values are defined in the .In openssl/obj_mac.h header file. .Sh RETURN VALUES All .Fn EC_GFp* functions and .Fn EC_GF2m_simple_method always return a const pointer to an .Vt EC_METHOD structure. .Pp .Fn EC_METHOD_get_field_type returns an integer that identifies the type of field the .Vt EC_METHOD structure supports. .Sh SEE ALSO .Xr BN_mod_mul_montgomery 3 , .Xr d2i_ECPKParameters 3 , .Xr EC_GROUP_copy 3 , .Xr EC_GROUP_new 3 , .Xr EC_KEY_new 3 , .Xr EC_POINT_add 3 , .Xr EC_POINT_new 3 .Sh HISTORY .Fn EC_GFp_simple_method and .Fn EC_GFp_mont_method first appeared in OpenSSL 0.9.7 and have been available since .Ox 3.2 . .Pp .Fn EC_GFp_nist_method , .Fn EC_GF2m_simple_method , and .Fn EC_METHOD_get_field_type first appeared in OpenSSL 0.9.8 and have been available since .Ox 4.5 . .Pp .Fn EC_GFp_nistp224_method , .Fn EC_GFp_nistp256_method , and .Fn EC_GFp_nistp521_method first appeared in OpenSSL 1.0.1 and have been available since .Ox 5.3 .