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EC_GROUP_NEW(3ossl) OpenSSL EC_GROUP_NEW(3ossl)
NAME
EC_GROUP_get_ecparameters, EC_GROUP_get_ecpkparameters,
EC_GROUP_new_from_params, EC_GROUP_new_from_ecparameters,
EC_GROUP_new_from_ecpkparameters, EC_GROUP_new, EC_GROUP_free,
EC_GROUP_clear_free, EC_GROUP_new_curve_GFp, EC_GROUP_new_curve_GF2m,
EC_GROUP_new_by_curve_name_ex, EC_GROUP_new_by_curve_name,
EC_GROUP_set_curve, EC_GROUP_get_curve, EC_GROUP_set_curve_GFp,
EC_GROUP_get_curve_GFp, EC_GROUP_set_curve_GF2m,
EC_GROUP_get_curve_GF2m, EC_get_builtin_curves, OSSL_EC_curve_nid2name
- Functions for creating and destroying EC_GROUP objects
SYNOPSIS
#include <openssl/ec.h>
EC_GROUP *EC_GROUP_new_from_params(const OSSL_PARAM params[],
OSSL_LIB_CTX *libctx, const char *propq);
EC_GROUP *EC_GROUP_new_from_ecparameters(const ECPARAMETERS *params);
EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params);
void EC_GROUP_free(EC_GROUP *group);
EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a,
const BIGNUM *b, BN_CTX *ctx);
EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a,
const BIGNUM *b, BN_CTX *ctx);
EC_GROUP *EC_GROUP_new_by_curve_name_ex(OSSL_LIB_CTX *libctx, const char *propq,
int nid);
EC_GROUP *EC_GROUP_new_by_curve_name(int nid);
int EC_GROUP_set_curve(EC_GROUP *group, const BIGNUM *p, const BIGNUM *a,
const BIGNUM *b, BN_CTX *ctx);
int EC_GROUP_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b,
BN_CTX *ctx);
ECPARAMETERS *EC_GROUP_get_ecparameters(const EC_GROUP *group,
ECPARAMETERS *params);
ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group,
ECPKPARAMETERS *params);
size_t EC_get_builtin_curves(EC_builtin_curve *r, size_t nitems);
const char *OSSL_EC_curve_nid2name(int nid);
The following functions have been deprecated since OpenSSL 3.0, and can
be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
version value, see openssl_user_macros(7):
EC_GROUP *EC_GROUP_new(const EC_METHOD *meth);
void EC_GROUP_clear_free(EC_GROUP *group);
int EC_GROUP_set_curve_GFp(EC_GROUP *group, const BIGNUM *p,
const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
int EC_GROUP_get_curve_GFp(const EC_GROUP *group, BIGNUM *p,
BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
int EC_GROUP_set_curve_GF2m(EC_GROUP *group, const BIGNUM *p,
const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
int EC_GROUP_get_curve_GF2m(const EC_GROUP *group, BIGNUM *p,
BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
y^2 mod p = x^3 +ax + b mod p
The second form is those defined over a binary field F2^m where the
elements of the field are integers of length at most m bits. For this
form the elliptic curve equation is modified to:
y^2 + xy = x^3 + ax^2 + b (where b != 0)
Operations in a binary field are performed relative to an irreducible
polynomial. All such curves with OpenSSL use a trinomial or a
pentanomial for this parameter.
Although deprecated since OpenSSL 3.0 and should no longer be used, a
new curve can be constructed by calling EC_GROUP_new(), using the
implementation provided by meth (see EC_GFp_simple_method(3)) and
associated with the library context ctx (see OSSL_LIB_CTX(3)). The ctx
parameter may be NULL in which case the default library context is
used. It is then necessary to call EC_GROUP_set_curve() to set the
curve parameters. Applications should instead use one of the other
EC_GROUP_new_* constructors.
EC_GROUP_new_from_params() creates a group with parameters specified by
params. The library context libctx (see OSSL_LIB_CTX(3)) and property
query string propq are used to fetch algorithms from providers. params
may be either a list of explicit params or a named group, The values
for ctx and propq may be NULL. The params that can be used are
described in EVP_PKEY-EC(7).
EC_GROUP_new_from_ecparameters() will create a group from the specified
params and EC_GROUP_new_from_ecpkparameters() will create a group from
the specific PK params.
EC_GROUP_set_curve() sets the curve parameters p, a and b. For a curve
over Fp p is the prime for the field. For a curve over F2^m p
represents the irreducible polynomial - each bit represents a term in
the polynomial. Therefore, there will either be three or five bits set
dependent on whether the polynomial is a trinomial or a pentanomial.
In either case, a and b represents the coefficients a and b from the
relevant equation introduced above.
EC_group_get_curve() obtains the previously set curve parameters.
EC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for
EC_GROUP_set_curve(). They are defined for backwards compatibility only
and should not be used.
EC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for
EC_GROUP_get_curve(). They are defined for backwards compatibility only
and should not be used.
The functions EC_GROUP_new_curve_GFp() and EC_GROUP_new_curve_GF2m()
are shortcuts for calling EC_GROUP_new() and then the
EC_GROUP_set_curve() function. An appropriate default implementation
method will be used.
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 EC_get_builtin_curves(). The parameter r should be an
total number of curves available. The EC_builtin_curve structure is
defined as follows:
typedef struct {
int nid;
const char *comment;
} EC_builtin_curve;
Each EC_builtin_curve item has a unique integer id (nid), and a human
readable comment string describing the curve.
In order to construct a built-in curve use the function
EC_GROUP_new_by_curve_name_ex() and provide the nid of the curve to be
constructed, the associated library context to be used in ctx (see
OSSL_LIB_CTX(3)) and any property query string in propq. The ctx value
may be NULL in which case the default library context is used. The
propq value may also be NULL.
EC_GROUP_new_by_curve_name() is the same as
EC_GROUP_new_by_curve_name_ex() except that the default library context
is always used along with a NULL property query string.
EC_GROUP_free() frees the memory associated with the EC_GROUP. If group
is NULL nothing is done.
EC_GROUP_clear_free() is deprecated: it was meant to destroy any
sensitive data held within the EC_GROUP and then free its memory, but
since all the data stored in the EC_GROUP is public anyway, this
function is unnecessary. Its use can be safely replaced with
EC_GROUP_free(). If group is NULL nothing is done.
OSSL_EC_curve_nid2name() converts a curve nid into the corresponding
name.
RETURN VALUES
All EC_GROUP_new* functions return a pointer to the newly constructed
group, or NULL on error.
EC_get_builtin_curves() returns the number of built-in curves that are
available.
EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(),
EC_GROUP_set_curve_GF2m(), EC_GROUP_get_curve_GF2m() return 1 on
success or 0 on error.
OSSL_EC_curve_nid2name() returns a character string constant, or NULL
on error.
SEE ALSO
crypto(7), EC_GROUP_copy(3), EC_POINT_new(3), EC_POINT_add(3),
EC_KEY_new(3), EC_GFp_simple_method(3), d2i_ECPKParameters(3),
OSSL_LIB_CTX(3), EVP_PKEY-EC(7)
HISTORY
o EC_GROUP_new() was deprecated in OpenSSL 3.0.
EC_GROUP_new_by_curve_name_ex() and EC_GROUP_new_from_params() were
added in OpenSSL 3.0.
EC_GROUP_set_curve_GF2m() and EC_GROUP_get_curve_GF2m() were deprecated in
OpenSSL 3.0; use EC_GROUP_set_curve() and EC_GROUP_get_curve() instead.
COPYRIGHT
Copyright 2013-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.0.11 2023-09-19 EC_GROUP_NEW(3ossl)