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.\" $OpenBSD: EC_GFp_simple_method.3,v 1.12 2023/04/27 08:47:04 tb Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Matt Caswell <matt@openssl.org>.
.\" 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. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.Dd $Mdocdate: April 27 2023 $
.Dt EC_GFP_SIMPLE_METHOD 3
.Os
.Sh NAME
.Nm EC_GFp_simple_method ,
.Nm EC_GFp_mont_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 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 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 ) .
.Pp
.Fn EC_METHOD_get_field_type
identifies what type of field the
.Vt EC_METHOD
structure supports.
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/objects.h
header file.
.Sh RETURN VALUES
All
.Fn EC_GFp*
functions 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_METHOD_get_field_type
first appeared in OpenSSL 0.9.8 and has been available since
.Ox 4.5 .
|
