137 lines
4.6 KiB
Groff
137 lines
4.6 KiB
Groff
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.\" $OpenBSD: EC_GFp_simple_method.3,v 1.12 2023/04/27 08:47:04 tb Exp $
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.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.\"
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.\" This file was written by Matt Caswell <matt@openssl.org>.
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.\" Copyright (c) 2013 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: April 27 2023 $
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.Dt EC_GFP_SIMPLE_METHOD 3
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.Os
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.Sh NAME
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.Nm EC_GFp_simple_method ,
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.Nm EC_GFp_mont_method ,
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.Nm EC_METHOD_get_field_type
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.Nd obtain EC_METHOD objects
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.Sh SYNOPSIS
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.In openssl/ec.h
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.Ft const EC_METHOD *
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.Fn EC_GFp_simple_method void
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.Ft const EC_METHOD *
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.Fn EC_GFp_mont_method void
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.Ft int
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.Fo EC_METHOD_get_field_type
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.Fa "const EC_METHOD *meth"
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.Fc
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.Sh DESCRIPTION
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The elliptic curve library provides a number of different
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implementations through a single common interface.
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Each implementation is optimised for different scenarios.
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An implementation is represented by an
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.Vt EC_METHOD
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structure.
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.Pp
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When constructing a curve using
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.Xr EC_GROUP_new 3 ,
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an implementation method must be provided.
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The functions described here all return a const pointer to an
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.Sy EC_METHOD
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structure that can be passed to
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.Xr EC_GROUP_new 3 .
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It is important that the correct implementation type for the form
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of curve selected is used.
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.Pp
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For Fp curves the lowest common denominator implementation is the
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.Fn EC_GFp_simple_method
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implementation.
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All other implementations are based on this one.
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.Fn EC_GFp_mont_method
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adds the use of Montgomery multiplication (see
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.Xr BN_mod_mul_montgomery 3 ) .
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.Pp
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.Fn EC_METHOD_get_field_type
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identifies what type of field the
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.Vt EC_METHOD
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structure supports.
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If the field type is Fp, then the value
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.Dv NID_X9_62_prime_field
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is returned.
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If the field type is F2^m, then the value
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.Dv NID_X9_62_characteristic_two_field
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is returned.
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These values are defined in the
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.In openssl/objects.h
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header file.
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.Sh RETURN VALUES
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All
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.Fn EC_GFp*
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functions always return a const pointer to an
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.Vt EC_METHOD
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structure.
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.Pp
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.Fn EC_METHOD_get_field_type
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returns an integer that identifies the type of field the
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.Vt EC_METHOD
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structure supports.
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.Sh SEE ALSO
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.Xr BN_mod_mul_montgomery 3 ,
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.Xr d2i_ECPKParameters 3 ,
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.Xr EC_GROUP_copy 3 ,
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.Xr EC_GROUP_new 3 ,
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.Xr EC_KEY_new 3 ,
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.Xr EC_POINT_add 3 ,
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.Xr EC_POINT_new 3
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.Sh HISTORY
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.Fn EC_GFp_simple_method
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and
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.Fn EC_GFp_mont_method
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first appeared in OpenSSL 0.9.7 and have been available since
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.Ox 3.2 .
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.Pp
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.Fn EC_METHOD_get_field_type
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first appeared in OpenSSL 0.9.8 and has been available since
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.Ox 4.5 .
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