.\" $OpenBSD: EC_GROUP_new.3,v 1.15 2023/04/27 09:35:20 tb Exp $ .\" OpenSSL 6328d367 Sat Jul 4 21:58:30 2020 +0200 .\" .\" 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: April 27 2023 $ .Dt EC_GROUP_NEW 3 .Os .Sh NAME .Nm EC_GROUP_new , .Nm EC_GROUP_free , .Nm EC_GROUP_clear_free , .Nm EC_GROUP_new_curve_GFp , .Nm EC_GROUP_new_by_curve_name , .Nm EC_GROUP_set_curve , .Nm EC_GROUP_get_curve , .Nm EC_GROUP_set_curve_GFp , .Nm EC_GROUP_get_curve_GFp , .Nm EC_get_builtin_curves .Nd create and destroy EC_GROUP objects .Sh SYNOPSIS .In openssl/ec.h .In openssl/bn.h .Ft EC_GROUP * .Fo EC_GROUP_new .Fa "const EC_METHOD *meth" .Fc .Ft void .Fo EC_GROUP_free .Fa "EC_GROUP *group" .Fc .Ft void .Fo EC_GROUP_clear_free .Fa "EC_GROUP *group" .Fc .Ft EC_GROUP * .Fo EC_GROUP_new_curve_GFp .Fa "const BIGNUM *p" .Fa "const BIGNUM *a" .Fa "const BIGNUM *b" .Fa "BN_CTX *ctx" .Fc .Ft EC_GROUP * .Fo EC_GROUP_new_by_curve_name .Fa "int nid" .Fc .Ft int .Fo EC_GROUP_set_curve .Fa "EC_GROUP *group" .Fa "const BIGNUM *p" .Fa "const BIGNUM *a" .Fa "const BIGNUM *b" .Fa "BN_CTX *ctx" .Fc .Ft int .Fo EC_GROUP_get_curve .Fa "const EC_GROUP *group" .Fa "BIGNUM *p" .Fa "BIGNUM *a" .Fa "BIGNUM *b" .Fa "BN_CTX *ctx" .Fc .Ft int .Fo EC_GROUP_set_curve_GFp .Fa "EC_GROUP *group" .Fa "const BIGNUM *p" .Fa "const BIGNUM *a" .Fa "const BIGNUM *b" .Fa "BN_CTX *ctx" .Fc .Ft int .Fo EC_GROUP_get_curve_GFp .Fa "const EC_GROUP *group" .Fa "BIGNUM *p" .Fa "BIGNUM *a" .Fa "BIGNUM *b" .Fa "BN_CTX *ctx" .Fc .Ft size_t .Fo EC_get_builtin_curves .Fa "EC_builtin_curve *r" .Fa "size_t nitems" .Fc .Sh DESCRIPTION The EC library provides functions for performing operations on elliptic curves over finite fields. In general, an elliptic curve satisfies an equation of the form: .Pp .Dl y^2 = x^3 + ax + b .Pp An .Vt EC_GROUP structure is used to represent the definition of an elliptic curve. A new curve can be constructed by calling .Fn EC_GROUP_new , using the implementation provided by .Fa meth (see .Xr EC_GFp_simple_method 3 ) . It is then necessary to call .Fn EC_GROUP_set_curve to set the curve parameters. .Pp .Fn EC_GROUP_set_curve sets the curve parameters .Fa p , .Fa a , and .Fa b , where .Fa a and .Fa b represent the coefficients of the curve equation. .Pp .Fn EC_GROUP_set_curve_GFp is a deprecated synonym for .Fn EC_GROUP_set_curve . .Pp .Fn EC_GROUP_get_curve obtains the previously set curve parameters. .Pp .Fn EC_GROUP_get_curve_GFp is a deprecated synonym for .Fn EC_GROUP_get_curve . .Pp The function .Fn EC_GROUP_new_curve_GFp is a shortcut for calling .Fn EC_GROUP_new and .Fn EC_GROUP_set_curve . An appropriate default implementation method will be used. .Pp Whilst the library can be used to create any curve using the functions described above, there are also a number of predefined curves that are available. In order to obtain a list of all of the predefined curves, call the function .Fn EC_get_builtin_curves . The parameter .Fa r should be an array of .Vt EC_builtin_cure structures of size .Fa nitems . The function will populate the .Fa r array with information about the builtin curves. If .Fa nitems is less than the total number of curves available, then the first .Fa nitems curves will be returned. Otherwise the total number of curves will be provided. The return value is the total number of curves available (whether that number has been populated in .Fa r or not). Passing a .Dv NULL .Fa r , or setting .Fa nitems to 0, will do nothing other than return the total number of curves available. The .Vt EC_builtin_curve structure is defined as follows: .Bd -literal typedef struct { int nid; const char *comment; } EC_builtin_curve; .Ed .Pp Each .Vt EC_builtin_curve item has a unique integer ID .Pq Fa nid and a human readable comment string describing the curve. .Pp In order to construct a builtin curve, use the function .Fn EC_GROUP_new_by_curve_name and provide the .Fa nid of the curve to be constructed. .Pp .Fn EC_GROUP_free frees the memory associated with the .Vt EC_GROUP . If .Fa group is a .Dv NULL pointer, no action occurs. .Pp .Fn EC_GROUP_clear_free destroys any sensitive data held within the .Vt EC_GROUP and then frees its memory. If .Fa group is a .Dv NULL pointer, no action occurs. .Sh RETURN VALUES All .Fn EC_GROUP_new* functions return a pointer to the newly constructed group or .Dv NULL on error. .Pp .Fn EC_get_builtin_curves returns the number of builtin curves that are available. .Pp .Fn EC_GROUP_set_curve , .Fn EC_GROUP_get_curve , .Fn EC_GROUP_set_curve_GFp , and .Fn EC_GROUP_get_curve_GFp return 1 on success or 0 on error. .Sh SEE ALSO .Xr crypto 3 , .Xr d2i_ECPKParameters 3 , .Xr EC_GFp_simple_method 3 , .Xr EC_GROUP_copy 3 , .Xr EC_KEY_new 3 , .Xr EC_POINT_add 3 , .Xr EC_POINT_new 3 , .Xr ECDH_compute_key 3 , .Xr ECDSA_SIG_new 3 .Sh HISTORY .Fn EC_GROUP_new , .Fn EC_GROUP_free , .Fn EC_GROUP_clear_free , .Fn EC_GROUP_new_curve_GFp , .Fn EC_GROUP_set_curve_GFp , and .Fn EC_GROUP_get_curve_GFp first appeared in OpenSSL 0.9.7 and have been available since .Ox 3.2 . .Pp .Fn EC_GROUP_new_by_curve_name , and .Fn EC_get_builtin_curves first appeared in OpenSSL 0.9.8 and have been available since .Ox 4.5 . .Fn EC_GROUP_set_curve and .Fn EC_GROUP_get_curve first appeared in OpenSSL 1.1.1 and have been available since .Ox 7.0 .