1.\" $OpenBSD: EC_GROUP_new.3,v 1.17 2024/04/27 07:41:47 tb Exp $ 2.\" OpenSSL 6328d367 Sat Jul 4 21:58:30 2020 +0200 3.\" 4.\" This file was written by Matt Caswell <matt@openssl.org>. 5.\" Copyright (c) 2013 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. 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Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: April 27 2024 $ 52.Dt EC_GROUP_NEW 3 53.Os 54.Sh NAME 55.Nm EC_GROUP_new , 56.Nm EC_GROUP_free , 57.Nm EC_GROUP_clear_free , 58.Nm EC_GROUP_new_curve_GFp , 59.Nm EC_GROUP_new_by_curve_name , 60.Nm EC_GROUP_set_curve , 61.Nm EC_GROUP_get_curve , 62.Nm EC_GROUP_set_curve_GFp , 63.Nm EC_GROUP_get_curve_GFp , 64.Nm EC_get_builtin_curves , 65.Nm EC_curve_nid2nist , 66.Nm EC_curve_nist2nid 67.Nd create and destroy EC_GROUP objects 68.Sh SYNOPSIS 69.In openssl/ec.h 70.In openssl/bn.h 71.Ft EC_GROUP * 72.Fo EC_GROUP_new 73.Fa "const EC_METHOD *meth" 74.Fc 75.Ft void 76.Fo EC_GROUP_free 77.Fa "EC_GROUP *group" 78.Fc 79.Ft void 80.Fo EC_GROUP_clear_free 81.Fa "EC_GROUP *group" 82.Fc 83.Ft EC_GROUP * 84.Fo EC_GROUP_new_curve_GFp 85.Fa "const BIGNUM *p" 86.Fa "const BIGNUM *a" 87.Fa "const BIGNUM *b" 88.Fa "BN_CTX *ctx" 89.Fc 90.Ft EC_GROUP * 91.Fo EC_GROUP_new_by_curve_name 92.Fa "int nid" 93.Fc 94.Ft int 95.Fo EC_GROUP_set_curve 96.Fa "EC_GROUP *group" 97.Fa "const BIGNUM *p" 98.Fa "const BIGNUM *a" 99.Fa "const BIGNUM *b" 100.Fa "BN_CTX *ctx" 101.Fc 102.Ft int 103.Fo EC_GROUP_get_curve 104.Fa "const EC_GROUP *group" 105.Fa "BIGNUM *p" 106.Fa "BIGNUM *a" 107.Fa "BIGNUM *b" 108.Fa "BN_CTX *ctx" 109.Fc 110.Ft int 111.Fo EC_GROUP_set_curve_GFp 112.Fa "EC_GROUP *group" 113.Fa "const BIGNUM *p" 114.Fa "const BIGNUM *a" 115.Fa "const BIGNUM *b" 116.Fa "BN_CTX *ctx" 117.Fc 118.Ft int 119.Fo EC_GROUP_get_curve_GFp 120.Fa "const EC_GROUP *group" 121.Fa "BIGNUM *p" 122.Fa "BIGNUM *a" 123.Fa "BIGNUM *b" 124.Fa "BN_CTX *ctx" 125.Fc 126.Ft size_t 127.Fo EC_get_builtin_curves 128.Fa "EC_builtin_curve *r" 129.Fa "size_t nitems" 130.Fc 131.Ft "const char *" 132.Fo EC_curve_nid2nist 133.Fa "int nid" 134.Fc 135.Ft int 136.Fo EC_curve_nist2nid 137.Fa "const char *name" 138.Fc 139.Sh DESCRIPTION 140The EC library provides functions for performing operations on 141elliptic curves in Weierstrass form. 142Such curves are defined over the prime field of order 143.Fa p 144and satisfy the Weierstrass equation with coefficients 145.Fa a 146and 147.Fa b 148.Pp 149.Dl y^2 = x^3 + ax + b 150.Pp 151An 152.Vt EC_GROUP 153structure is used to represent the definition of an elliptic curve. 154A new curve can be constructed by calling 155.Fn EC_GROUP_new , 156using the implementation provided by 157.Fa meth 158(see 159.Xr EC_GFp_simple_method 3 ) . 160It is then necessary to call 161.Fn EC_GROUP_set_curve 162to set the curve parameters. 163.Pp 164.Fn EC_GROUP_set_curve 165sets the curve parameters 166.Fa p , 167.Fa a , 168and 169.Fa b , 170where 171.Fa a 172and 173.Fa b 174represent the coefficients of the curve equation. 175.Pp 176.Fn EC_GROUP_set_curve_GFp 177is a deprecated synonym for 178.Fn EC_GROUP_set_curve . 179.Pp 180.Fn EC_GROUP_get_curve 181obtains the previously set curve parameters. 182.Pp 183.Fn EC_GROUP_get_curve_GFp 184is a deprecated synonym for 185.Fn EC_GROUP_get_curve . 186.Pp 187The function 188.Fn EC_GROUP_new_curve_GFp 189is a shortcut for calling 190.Fn EC_GROUP_new 191and 192.Fn EC_GROUP_set_curve . 193An appropriate default implementation method will be used. 194.Pp 195Whilst the library can be used to create any curve using the functions 196described above, there are also a number of predefined curves that are 197available. 198In order to obtain a list of all of the predefined curves, call the 199function 200.Fn EC_get_builtin_curves . 201The parameter 202.Fa r 203should be an array of 204.Vt EC_builtin_cure 205structures of size 206.Fa nitems . 207The function will populate the 208.Fa r 209array with information about the builtin curves. 210If 211.Fa nitems 212is less than the total number of curves available, then the first 213.Fa nitems 214curves will be returned. 215Otherwise the total number of curves will be provided. 216The return value is the total number of curves available (whether that 217number has been populated in 218.Fa r 219or not). 220Passing a 221.Dv NULL 222.Fa r , 223or setting 224.Fa nitems 225to 0, will do nothing other than return the total number of curves 226available. 227The 228.Vt EC_builtin_curve 229structure is defined as follows: 230.Bd -literal 231typedef struct { 232 int nid; 233 const char *comment; 234} EC_builtin_curve; 235.Ed 236.Pp 237Each 238.Vt EC_builtin_curve 239item has a unique integer ID 240.Pq Fa nid 241and a human readable comment string describing the curve. 242.Pp 243In order to construct a builtin curve, use the function 244.Fn EC_GROUP_new_by_curve_name 245and provide the 246.Fa nid 247of the curve to be constructed. 248.Pp 249.Fn EC_GROUP_free 250frees the memory associated with the 251.Vt EC_GROUP . 252If 253.Fa group 254is a 255.Dv NULL 256pointer, no action occurs. 257.Pp 258.Fn EC_GROUP_clear_free 259destroys any sensitive data held within the 260.Vt EC_GROUP 261and then frees its memory. 262If 263.Fa group 264is a 265.Dv NULL 266pointer, no action occurs. 267.Pp 268Some builtin curves can be identified by their NIST name 269in addition to a numerical identifier (NID). 270.Fn EC_curve_nid2nist 271and 272.Fn EC_curve_nist2nid 273translate between the two. 274The five built-in prime curves are: 275.Pp 276.Bl -column "NIST name" NID_X9_62_prime256v1 "deprecated in SP800-186" -compact 277.It No NIST Fa name Ta Em ASN.1 NID Ta Em notes 278.It Qq P-192 Ta Dv NID_X9_62_prime192v1 Ta No deprecated in SP800-186 279.It Qq P-224 Ta Dv NID_secp224r1 Ta 280.It Qq P-256 Ta Dv NID_X9_62_prime256v1 Ta 281.It Qq P-384 Ta Dv NID_secp384r1 Ta 282.It Qq P-521 Ta Dv NID_secp521r1 Ta 283.El 284.Pp 285.Fn EC_curve_nid2nist 286and 287.Fn EC_curve_nist2nid 288also accept the ten binary curves defined in FIPS\& 186-4 289and deprecated in SP800-186, 290although they no longer correspond to builtin curves in LibreSSL. 291.Sh RETURN VALUES 292All 293.Fn EC_GROUP_new* 294functions return a pointer to the newly constructed group or 295.Dv NULL 296on error. 297.Pp 298.Fn EC_get_builtin_curves 299returns the number of builtin curves that are available. 300.Pp 301.Fn EC_curve_nid2nist 302returns a string constant containing the NIST name if 303.Fa nid 304identifies a NIST curve or 305.Dv NULL 306otherwise. 307.Pp 308.Fn EC_curve_nist2nid 309returns the NID corresponding to the NIST curve 310.Fa name , 311or 312.Dv NID_undef . 313.Pp 314.Fn EC_GROUP_set_curve , 315.Fn EC_GROUP_get_curve , 316.Fn EC_GROUP_set_curve_GFp , 317and 318.Fn EC_GROUP_get_curve_GFp 319return 1 on success or 0 on error. 320.Sh SEE ALSO 321.Xr crypto 3 , 322.Xr d2i_ECPKParameters 3 , 323.Xr EC_GFp_simple_method 3 , 324.Xr EC_GROUP_copy 3 , 325.Xr EC_KEY_new 3 , 326.Xr EC_POINT_add 3 , 327.Xr EC_POINT_new 3 , 328.Xr ECDH_compute_key 3 , 329.Xr ECDSA_SIG_new 3 330.Sh HISTORY 331.Fn EC_GROUP_new , 332.Fn EC_GROUP_free , 333.Fn EC_GROUP_clear_free , 334.Fn EC_GROUP_new_curve_GFp , 335.Fn EC_GROUP_set_curve_GFp , 336and 337.Fn EC_GROUP_get_curve_GFp 338first appeared in OpenSSL 0.9.7 and have been available since 339.Ox 3.2 . 340.Pp 341.Fn EC_GROUP_new_by_curve_name 342and 343.Fn EC_get_builtin_curves 344first appeared in OpenSSL 0.9.8 and have been available since 345.Ox 4.5 . 346.Fn EC_curve_nid2nist , 347and 348.Fn EC_curve_nist2nid 349first appeared in OpenSSL 1.1.0 and have been available since 350.Ox 5.8 . 351.Pp 352.Fn EC_GROUP_set_curve 353and 354.Fn EC_GROUP_get_curve 355first appeared in OpenSSL 1.1.1 and have been available since 356.Ox 7.0 . 357