352 lines
8.8 KiB
Groff
352 lines
8.8 KiB
Groff
.\" $OpenBSD: EC_GROUP_new.3,v 1.16 2024/04/26 14:23:03 tb Exp $
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.\" OpenSSL 6328d367 Sat Jul 4 21:58:30 2020 +0200
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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 26 2024 $
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.Dt EC_GROUP_NEW 3
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.Os
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.Sh NAME
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.Nm EC_GROUP_new ,
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.Nm EC_GROUP_free ,
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.Nm EC_GROUP_clear_free ,
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.Nm EC_GROUP_new_curve_GFp ,
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.Nm EC_GROUP_new_by_curve_name ,
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.Nm EC_GROUP_set_curve ,
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.Nm EC_GROUP_get_curve ,
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.Nm EC_GROUP_set_curve_GFp ,
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.Nm EC_GROUP_get_curve_GFp ,
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.Nm EC_get_builtin_curves ,
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.Nm EC_curve_nid2nist ,
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.Nm EC_curve_nist2nid
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.Nd create and destroy EC_GROUP objects
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.Sh SYNOPSIS
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.In openssl/ec.h
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.In openssl/bn.h
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.Ft EC_GROUP *
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.Fo EC_GROUP_new
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.Fa "const EC_METHOD *meth"
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.Fc
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.Ft void
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.Fo EC_GROUP_free
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.Fa "EC_GROUP *group"
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.Fc
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.Ft void
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.Fo EC_GROUP_clear_free
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.Fa "EC_GROUP *group"
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.Fc
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.Ft EC_GROUP *
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.Fo EC_GROUP_new_curve_GFp
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.Fa "const BIGNUM *p"
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.Fa "const BIGNUM *a"
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.Fa "const BIGNUM *b"
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.Fa "BN_CTX *ctx"
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.Fc
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.Ft EC_GROUP *
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.Fo EC_GROUP_new_by_curve_name
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.Fa "int nid"
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.Fc
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.Ft int
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.Fo EC_GROUP_set_curve
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.Fa "EC_GROUP *group"
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.Fa "const BIGNUM *p"
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.Fa "const BIGNUM *a"
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.Fa "const BIGNUM *b"
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.Fa "BN_CTX *ctx"
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.Fc
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.Ft int
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.Fo EC_GROUP_get_curve
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.Fa "const EC_GROUP *group"
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.Fa "BIGNUM *p"
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.Fa "BIGNUM *a"
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.Fa "BIGNUM *b"
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.Fa "BN_CTX *ctx"
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.Fc
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.Ft int
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.Fo EC_GROUP_set_curve_GFp
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.Fa "EC_GROUP *group"
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.Fa "const BIGNUM *p"
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.Fa "const BIGNUM *a"
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.Fa "const BIGNUM *b"
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.Fa "BN_CTX *ctx"
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.Fc
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.Ft int
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.Fo EC_GROUP_get_curve_GFp
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.Fa "const EC_GROUP *group"
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.Fa "BIGNUM *p"
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.Fa "BIGNUM *a"
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.Fa "BIGNUM *b"
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.Fa "BN_CTX *ctx"
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.Fc
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.Ft size_t
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.Fo EC_get_builtin_curves
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.Fa "EC_builtin_curve *r"
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.Fa "size_t nitems"
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.Fc
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.Ft "const char *"
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.Fo EC_curve_nid2nist
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.Fa "int nid"
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.Fc
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.Ft int
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.Fo EC_curve_nist2nid
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.Fa "const char *name"
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.Fc
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.Sh DESCRIPTION
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The EC library provides functions for performing operations on
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elliptic curves over finite fields.
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In general, an elliptic curve satisfies an equation of the form:
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.Pp
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.Dl y^2 = x^3 + ax + b
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.Pp
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An
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.Vt EC_GROUP
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structure is used to represent the definition of an elliptic curve.
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A new curve can be constructed by calling
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.Fn EC_GROUP_new ,
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using the implementation provided by
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.Fa meth
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(see
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.Xr EC_GFp_simple_method 3 ) .
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It is then necessary to call
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.Fn EC_GROUP_set_curve
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to set the curve parameters.
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.Pp
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.Fn EC_GROUP_set_curve
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sets the curve parameters
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.Fa p ,
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.Fa a ,
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and
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.Fa b ,
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where
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.Fa a
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and
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.Fa b
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represent the coefficients of the curve equation.
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.Pp
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.Fn EC_GROUP_set_curve_GFp
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is a deprecated synonym for
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.Fn EC_GROUP_set_curve .
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.Pp
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.Fn EC_GROUP_get_curve
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obtains the previously set curve parameters.
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.Pp
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.Fn EC_GROUP_get_curve_GFp
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is a deprecated synonym for
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.Fn EC_GROUP_get_curve .
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.Pp
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The function
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.Fn EC_GROUP_new_curve_GFp
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is a shortcut for calling
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.Fn EC_GROUP_new
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and
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.Fn EC_GROUP_set_curve .
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An appropriate default implementation method will be used.
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.Pp
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Whilst the library can be used to create any curve using the functions
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described above, there are also a number of predefined curves that are
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available.
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In order to obtain a list of all of the predefined curves, call the
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function
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.Fn EC_get_builtin_curves .
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The parameter
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.Fa r
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should be an array of
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.Vt EC_builtin_cure
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structures of size
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.Fa nitems .
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The function will populate the
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.Fa r
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array with information about the builtin curves.
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If
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.Fa nitems
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is less than the total number of curves available, then the first
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.Fa nitems
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curves will be returned.
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Otherwise the total number of curves will be provided.
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The return value is the total number of curves available (whether that
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number has been populated in
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.Fa r
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or not).
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Passing a
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.Dv NULL
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.Fa r ,
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or setting
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.Fa nitems
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to 0, will do nothing other than return the total number of curves
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available.
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The
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.Vt EC_builtin_curve
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structure is defined as follows:
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.Bd -literal
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typedef struct {
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int nid;
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const char *comment;
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} EC_builtin_curve;
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.Ed
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.Pp
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Each
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.Vt EC_builtin_curve
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item has a unique integer ID
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.Pq Fa nid
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and a human readable comment string describing the curve.
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.Pp
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In order to construct a builtin curve, use the function
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.Fn EC_GROUP_new_by_curve_name
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and provide the
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.Fa nid
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of the curve to be constructed.
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.Pp
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.Fn EC_GROUP_free
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frees the memory associated with the
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.Vt EC_GROUP .
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If
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.Fa group
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is a
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.Dv NULL
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pointer, no action occurs.
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.Pp
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.Fn EC_GROUP_clear_free
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destroys any sensitive data held within the
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.Vt EC_GROUP
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and then frees its memory.
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If
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.Fa group
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is a
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.Dv NULL
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pointer, no action occurs.
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.Pp
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Some builtin curves can be identified by their NIST name
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in addition to a numerical identifier (NID).
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.Fn EC_curve_nid2nist
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and
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.Fn EC_curve_nist2nid
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translate between the two.
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The five built-in prime curves are:
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.Pp
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.Bl -column "NIST name" NID_X9_62_prime256v1 "deprecated in SP800-186" -compact
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.It No NIST Fa name Ta Em ASN.1 NID Ta Em notes
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.It Qq P-192 Ta Dv NID_X9_62_prime192v1 Ta No deprecated in SP800-186
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.It Qq P-224 Ta Dv NID_secp224r1 Ta
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.It Qq P-256 Ta Dv NID_X9_62_prime256v1 Ta
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.It Qq P-384 Ta Dv NID_secp384r1 Ta
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.It Qq P-521 Ta Dv NID_secp521r1 Ta
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.El
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.Pp
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.Fn EC_curve_nid2nist
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and
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.Fn EC_curve_nist2nid
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also accept the ten binary curves defined in FIPS\& 186-4
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and deprecated in SP800-186,
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although they no longer correspond to builtin curves in LibreSSL.
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.Sh RETURN VALUES
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All
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.Fn EC_GROUP_new*
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functions return a pointer to the newly constructed group or
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.Dv NULL
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on error.
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.Pp
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.Fn EC_get_builtin_curves
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returns the number of builtin curves that are available.
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.Pp
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.Fn EC_curve_nid2nist
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returns a string constant containing the NIST name if
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.Fa nid
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identifies a NIST curve or
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.Dv NULL
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otherwise.
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.Pp
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.Fn EC_curve_nist2nid
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returns the NID corresponding to the NIST curve
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.Fa name ,
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or
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.Dv NID_undef .
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.Pp
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.Fn EC_GROUP_set_curve ,
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.Fn EC_GROUP_get_curve ,
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.Fn EC_GROUP_set_curve_GFp ,
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and
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.Fn EC_GROUP_get_curve_GFp
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return 1 on success or 0 on error.
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.Sh SEE ALSO
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.Xr crypto 3 ,
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.Xr d2i_ECPKParameters 3 ,
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.Xr EC_GFp_simple_method 3 ,
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.Xr EC_GROUP_copy 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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.Xr ECDH_compute_key 3 ,
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.Xr ECDSA_SIG_new 3
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.Sh HISTORY
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.Fn EC_GROUP_new ,
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.Fn EC_GROUP_free ,
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.Fn EC_GROUP_clear_free ,
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.Fn EC_GROUP_new_curve_GFp ,
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.Fn EC_GROUP_set_curve_GFp ,
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and
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.Fn EC_GROUP_get_curve_GFp
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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_GROUP_new_by_curve_name
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and
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.Fn EC_get_builtin_curves
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first appeared in OpenSSL 0.9.8 and have been available since
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.Ox 4.5 .
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.Fn EC_curve_nid2nist ,
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and
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.Fn EC_curve_nist2nid
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first appeared in OpenSSL 1.1.0 and have been available since
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.Ox 5.8 .
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.Pp
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.Fn EC_GROUP_set_curve
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and
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.Fn EC_GROUP_get_curve
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first appeared in OpenSSL 1.1.1 and have been available since
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.Ox 7.0 .
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