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_to_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);
OSSL_PARAM *EC_GROUP_to_params(const EC_GROUP *group, OSSL_LIB_CTX *libctx,
const char *propq, BN_CTX *bnctx);
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);
DESCRIPTION
Within the library there are two forms of elliptic curve that are of
interest. The first form is those defined over the prime field Fp. The
elements of Fp are the integers 0 to p-1, where p is a prime number.
This gives us a revised elliptic curve equation as follows:
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(3), 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_to_params creates an OSSL_PARAM array with the corresponding
parameters describing the given EC_GROUP. The resulting parameters may
contain parameters describing a named or explicit curve depending on
the EC_GROUP. The library context libctx (see OSSL_LIB_CTX(3)) and
property query string propq are used to fetch algorithms from
providers. bnctx is an optional preallocated BN_CTX (to save the
overhead of allocating and freeing the structure in a loop). The
values for libctx, propq and bnctx may be NULL. The caller is
responsible for freeing the OSSL_PARAM pointer returned.
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(3) 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
array of EC_builtin_curve structures of size nitems. The function will
populate the r array with information about the built-in curves. If
nitems is less than the total number of curves available, then the
first 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 r or not). Passing
a NULL r, or setting nitems to 0 will do nothing other than return the
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
EC_GROUP_new(3) 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.
o EC_GROUP_clear_free() was deprecated in OpenSSL 3.0; use
EC_GROUP_free() instead.
o
EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(),
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 2013-2023 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>.
3.3.2 2024-09-04 EC_GROUP_NEW(3ossl)
openssl 3.3.2 - Generated Tue Sep 10 13:26:54 CDT 2024