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Title "EC_GROUP_NEW 3ossl"
way too many mistakes in technical documents.
The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):
.Vb 2 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); .Ve
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 \fBirreducible 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 \s-1OSSL_LIB_CTX\s0\|(3)). The ctx parameter may be \s-1NULL\s0 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.
\fBEC_GROUP_new_from_params() creates a group with parameters specified by params. The library context libctx (see \s-1OSSL_LIB_CTX\s0\|(3)) and property query string \fIpropq are used to fetch algorithms from providers. \fIparams may be either a list of explicit params or a named group, The values for ctx and propq may be \s-1NULL.\s0 The params that can be used are described in \fB\s-1EVP_PKEY-EC\s0(7).
\fBEC_GROUP_new_from_ecparameters() will create a group from the specified params and \fBEC_GROUP_new_from_ecpkparameters() will create a group from the specific \s-1PK\s0 \fIparams.
\fBEC_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.
\fBEC_group_get_curve() obtains the previously set curve parameters.
\fBEC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for \fBEC_GROUP_set_curve(). They are defined for backwards compatibility only and should not be used.
\fBEC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for \fBEC_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 \fBEC_get_builtin_curves(). The parameter r should be an array of EC_builtin_curve structures of size nitems. The function will populate the \fIr 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 \s-1NULL\s0 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:
.Vb 4 typedef struct { int nid; const char *comment; } EC_builtin_curve; .Ve
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 \fBEC_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 \s-1OSSL_LIB_CTX\s0\|(3)) and any property query string in propq. The ctx value may be \s-1NULL\s0 in which case the default library context is used. The propq value may also be \s-1NULL.\s0
\fBEC_GROUP_new_by_curve_name() is the same as \fBEC_GROUP_new_by_curve_name_ex() except that the default library context is always used along with a \s-1NULL\s0 property query string.
\fBEC_GROUP_free() frees the memory associated with the \s-1EC_GROUP.\s0 If group is \s-1NULL\s0 nothing is done.
\fBEC_GROUP_clear_free() is deprecated: it was meant to destroy any sensitive data held within the \s-1EC_GROUP\s0 and then free its memory, but since all the data stored in the \s-1EC_GROUP\s0 is public anyway, this function is unnecessary. Its use can be safely replaced with EC_GROUP_free(). If group is \s-1NULL\s0 nothing is done.
\fBOSSL_EC_curve_nid2name() converts a curve nid into the corresponding name.
\fBEC_get_builtin_curves() returns the number of built-in curves that are available.
\fBEC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(), EC_GROUP_set_curve_GF2m(), \fBEC_GROUP_get_curve_GF2m() return 1 on success or 0 on error.
\fBOSSL_EC_curve_nid2name() returns a character string constant, or \s-1NULL\s0 on error.
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.