1=pod 2 3=head1 NAME 4 5EC_GROUP_get_ecparameters, 6EC_GROUP_get_ecpkparameters, 7EC_GROUP_new_from_params, 8EC_GROUP_new_from_ecparameters, 9EC_GROUP_new_from_ecpkparameters, 10EC_GROUP_new, 11EC_GROUP_free, 12EC_GROUP_clear_free, 13EC_GROUP_new_curve_GFp, 14EC_GROUP_new_curve_GF2m, 15EC_GROUP_new_by_curve_name_ex, 16EC_GROUP_new_by_curve_name, 17EC_GROUP_set_curve, 18EC_GROUP_get_curve, 19EC_GROUP_set_curve_GFp, 20EC_GROUP_get_curve_GFp, 21EC_GROUP_set_curve_GF2m, 22EC_GROUP_get_curve_GF2m, 23EC_get_builtin_curves, 24OSSL_EC_curve_nid2name - 25Functions for creating and destroying EC_GROUP objects 26 27=head1 SYNOPSIS 28 29 #include <openssl/ec.h> 30 31 EC_GROUP *EC_GROUP_new_from_params(const OSSL_PARAM params[], 32 OSSL_LIB_CTX *libctx, const char *propq); 33 EC_GROUP *EC_GROUP_new_from_ecparameters(const ECPARAMETERS *params); 34 EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params); 35 void EC_GROUP_free(EC_GROUP *group); 36 37 EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, 38 const BIGNUM *b, BN_CTX *ctx); 39 EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a, 40 const BIGNUM *b, BN_CTX *ctx); 41 EC_GROUP *EC_GROUP_new_by_curve_name_ex(OSSL_LIB_CTX *libctx, const char *propq, 42 int nid); 43 EC_GROUP *EC_GROUP_new_by_curve_name(int nid); 44 45 int EC_GROUP_set_curve(EC_GROUP *group, const BIGNUM *p, const BIGNUM *a, 46 const BIGNUM *b, BN_CTX *ctx); 47 int EC_GROUP_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b, 48 BN_CTX *ctx); 49 50 ECPARAMETERS *EC_GROUP_get_ecparameters(const EC_GROUP *group, 51 ECPARAMETERS *params); 52 ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group, 53 ECPKPARAMETERS *params); 54 55 size_t EC_get_builtin_curves(EC_builtin_curve *r, size_t nitems); 56 const char *OSSL_EC_curve_nid2name(int nid); 57 58The following functions have been deprecated since OpenSSL 3.0, and can be 59hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value, 60see L<openssl_user_macros(7)>: 61 62 EC_GROUP *EC_GROUP_new(const EC_METHOD *meth); 63 void EC_GROUP_clear_free(EC_GROUP *group); 64 65 int EC_GROUP_set_curve_GFp(EC_GROUP *group, const BIGNUM *p, 66 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx); 67 int EC_GROUP_get_curve_GFp(const EC_GROUP *group, BIGNUM *p, 68 BIGNUM *a, BIGNUM *b, BN_CTX *ctx); 69 int EC_GROUP_set_curve_GF2m(EC_GROUP *group, const BIGNUM *p, 70 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx); 71 int EC_GROUP_get_curve_GF2m(const EC_GROUP *group, BIGNUM *p, 72 BIGNUM *a, BIGNUM *b, BN_CTX *ctx); 73 74=head1 DESCRIPTION 75 76Within the library there are two forms of elliptic curve that are of interest. 77The first form is those defined over the prime field Fp. The elements of Fp are 78the integers 0 to p-1, where p is a prime number. This gives us a revised 79elliptic curve equation as follows: 80 81y^2 mod p = x^3 +ax + b mod p 82 83The second form is those defined over a binary field F2^m where the elements of 84the field are integers of length at most m bits. For this form the elliptic 85curve equation is modified to: 86 87y^2 + xy = x^3 + ax^2 + b (where b != 0) 88 89Operations in a binary field are performed relative to an 90B<irreducible polynomial>. All such curves with OpenSSL use a trinomial or a 91pentanomial for this parameter. 92 93Although deprecated since OpenSSL 3.0 and should no longer be used, 94a new curve can be constructed by calling EC_GROUP_new(), using the 95implementation provided by I<meth> (see L<EC_GFp_simple_method(3)>) and 96associated with the library context I<ctx> (see L<OSSL_LIB_CTX(3)>). 97The I<ctx> parameter may be NULL in which case the default library context is 98used. 99It is then necessary to call EC_GROUP_set_curve() to set the curve parameters. 100Applications should instead use one of the other EC_GROUP_new_* constructors. 101 102EC_GROUP_new_from_params() creates a group with parameters specified by I<params>. 103The library context I<libctx> (see L<OSSL_LIB_CTX(3)>) and property query string 104I<propq> are used to fetch algorithms from providers. 105I<params> may be either a list of explicit params or a named group, 106The values for I<ctx> and I<propq> may be NULL. 107The I<params> that can be used are described in 108L<B<EVP_PKEY-EC>(7)|EVP_PKEY-EC(7)/Common EC parameters>. 109 110EC_GROUP_new_from_ecparameters() will create a group from the 111specified I<params> and 112EC_GROUP_new_from_ecpkparameters() will create a group from the specific PK 113I<params>. 114 115EC_GROUP_set_curve() sets the curve parameters I<p>, I<a> and I<b>. For a curve 116over Fp I<p> is the prime for the field. For a curve over F2^m I<p> represents 117the irreducible polynomial - each bit represents a term in the polynomial. 118Therefore, there will either be three or five bits set dependent on whether the 119polynomial is a trinomial or a pentanomial. 120In either case, I<a> and I<b> represents the coefficients a and b from the 121relevant equation introduced above. 122 123EC_group_get_curve() obtains the previously set curve parameters. 124 125EC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for 126EC_GROUP_set_curve(). They are defined for backwards compatibility only and 127should not be used. 128 129EC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for 130EC_GROUP_get_curve(). They are defined for backwards compatibility only and 131should not be used. 132 133The functions EC_GROUP_new_curve_GFp() and EC_GROUP_new_curve_GF2m() are 134shortcuts for calling EC_GROUP_new() and then the EC_GROUP_set_curve() function. 135An appropriate default implementation method will be used. 136 137Whilst the library can be used to create any curve using the functions described 138above, there are also a number of predefined curves that are available. In order 139to obtain a list of all of the predefined curves, call the function 140EC_get_builtin_curves(). The parameter I<r> should be an array of 141EC_builtin_curve structures of size I<nitems>. The function will populate the 142I<r> array with information about the built-in curves. If I<nitems> is less than 143the total number of curves available, then the first I<nitems> curves will be 144returned. Otherwise the total number of curves will be provided. The return 145value is the total number of curves available (whether that number has been 146populated in I<r> or not). Passing a NULL I<r>, or setting I<nitems> to 0 will 147do nothing other than return the total number of curves available. 148The EC_builtin_curve structure is defined as follows: 149 150 typedef struct { 151 int nid; 152 const char *comment; 153 } EC_builtin_curve; 154 155Each EC_builtin_curve item has a unique integer id (I<nid>), and a human 156readable comment string describing the curve. 157 158In order to construct a built-in curve use the function 159EC_GROUP_new_by_curve_name_ex() and provide the I<nid> of the curve to 160be constructed, the associated library context to be used in I<ctx> (see 161L<OSSL_LIB_CTX(3)>) and any property query string in I<propq>. The I<ctx> value 162may be NULL in which case the default library context is used. The I<propq> 163value may also be NULL. 164 165EC_GROUP_new_by_curve_name() is the same as 166EC_GROUP_new_by_curve_name_ex() except that the default library context 167is always used along with a NULL property query string. 168 169EC_GROUP_free() frees the memory associated with the EC_GROUP. 170If I<group> is NULL nothing is done. 171 172EC_GROUP_clear_free() is deprecated: it was meant to destroy any sensitive data 173held within the EC_GROUP and then free its memory, but since all the data stored 174in the EC_GROUP is public anyway, this function is unnecessary. 175Its use can be safely replaced with EC_GROUP_free(). 176If I<group> is NULL nothing is done. 177 178OSSL_EC_curve_nid2name() converts a curve I<nid> into the corresponding name. 179 180=head1 RETURN VALUES 181 182All EC_GROUP_new* functions return a pointer to the newly constructed group, or 183NULL on error. 184 185EC_get_builtin_curves() returns the number of built-in curves that are 186available. 187 188EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(), EC_GROUP_set_curve_GF2m(), 189EC_GROUP_get_curve_GF2m() return 1 on success or 0 on error. 190 191OSSL_EC_curve_nid2name() returns a character string constant, or NULL on error. 192 193=head1 SEE ALSO 194 195L<crypto(7)>, L<EC_GROUP_copy(3)>, 196L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>, 197L<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>, 198L<OSSL_LIB_CTX(3)>, L<EVP_PKEY-EC(7)> 199 200=head1 HISTORY 201 202=over 2 203 204=item * 205 206EC_GROUP_new() was deprecated in OpenSSL 3.0. 207 208EC_GROUP_new_by_curve_name_ex() and EC_GROUP_new_from_params() were 209added in OpenSSL 3.0. 210 211=item * 212 213EC_GROUP_clear_free() was deprecated in OpenSSL 3.0; use EC_GROUP_free() 214instead. 215 216=item * 217 218 EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(), 219 EC_GROUP_set_curve_GF2m() and EC_GROUP_get_curve_GF2m() were deprecated in 220 OpenSSL 3.0; use EC_GROUP_set_curve() and EC_GROUP_get_curve() instead. 221 222=back 223 224=head1 COPYRIGHT 225 226Copyright 2013-2021 The OpenSSL Project Authors. All Rights Reserved. 227 228Licensed under the Apache License 2.0 (the "License"). You may not use 229this file except in compliance with the License. You can obtain a copy 230in the file LICENSE in the source distribution or at 231L<https://www.openssl.org/source/license.html>. 232 233=cut 234