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1 | =pod | |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | EC_GROUP_get_ecparameters, | |
6 | EC_GROUP_get_ecpkparameters, | |
7 | EC_GROUP_new, | |
8 | EC_GROUP_new_from_ecparameters, | |
9 | EC_GROUP_new_from_ecpkparameters, | |
10 | EC_GROUP_free, | |
11 | EC_GROUP_clear_free, | |
12 | EC_GROUP_new_curve_GFp, | |
13 | EC_GROUP_new_curve_GF2m, | |
14 | EC_GROUP_new_by_curve_name_ex, | |
15 | EC_GROUP_new_by_curve_name, | |
16 | EC_GROUP_set_curve, | |
17 | EC_GROUP_get_curve, | |
18 | EC_GROUP_set_curve_GFp, | |
19 | EC_GROUP_get_curve_GFp, | |
20 | EC_GROUP_set_curve_GF2m, | |
21 | EC_GROUP_get_curve_GF2m, | |
22 | EC_get_builtin_curves - Functions for creating and destroying EC_GROUP | |
23 | objects | |
24 | ||
25 | =head1 SYNOPSIS | |
26 | ||
27 | #include <openssl/ec.h> | |
28 | ||
29 | EC_GROUP *EC_GROUP_new_from_ecparameters(const ECPARAMETERS *params) | |
30 | EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params) | |
31 | void EC_GROUP_free(EC_GROUP *group); | |
32 | ||
33 | EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a, | |
34 | const BIGNUM *b, BN_CTX *ctx); | |
35 | EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a, | |
36 | const BIGNUM *b, BN_CTX *ctx); | |
37 | EC_GROUP *EC_GROUP_new_by_curve_name_ex(OPENSSL_CTX *libctx, int nid); | |
38 | EC_GROUP *EC_GROUP_new_by_curve_name(int nid); | |
39 | ||
40 | int EC_GROUP_set_curve(EC_GROUP *group, const BIGNUM *p, const BIGNUM *a, | |
41 | const BIGNUM *b, BN_CTX *ctx); | |
42 | int EC_GROUP_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b, | |
43 | BN_CTX *ctx); | |
44 | int EC_GROUP_set_curve_GFp(EC_GROUP *group, const BIGNUM *p, | |
45 | const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx); | |
46 | int EC_GROUP_get_curve_GFp(const EC_GROUP *group, BIGNUM *p, | |
47 | BIGNUM *a, BIGNUM *b, BN_CTX *ctx); | |
48 | int EC_GROUP_set_curve_GF2m(EC_GROUP *group, const BIGNUM *p, | |
49 | const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx); | |
50 | int EC_GROUP_get_curve_GF2m(const EC_GROUP *group, BIGNUM *p, | |
51 | BIGNUM *a, BIGNUM *b, BN_CTX *ctx); | |
52 | ||
53 | ECPARAMETERS *EC_GROUP_get_ecparameters(const EC_GROUP *group, ECPARAMETERS *params) | |
54 | ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group, ECPKPARAMETERS *params) | |
55 | ||
56 | size_t EC_get_builtin_curves(EC_builtin_curve *r, size_t nitems); | |
57 | ||
58 | Deprecated since OpenSSL 3.0, can be hidden entirely by defining | |
59 | B<OPENSSL_API_COMPAT> with a suitable version value, see | |
60 | 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 | =head1 DESCRIPTION | |
66 | ||
67 | Within the library there are two forms of elliptic curve that are of interest. | |
68 | The first form is those defined over the prime field Fp. The elements of Fp are | |
69 | the integers 0 to p-1, where p is a prime number. This gives us a revised | |
70 | elliptic curve equation as follows: | |
71 | ||
72 | y^2 mod p = x^3 +ax + b mod p | |
73 | ||
74 | The second form is those defined over a binary field F2^m where the elements of | |
75 | the field are integers of length at most m bits. For this form the elliptic | |
76 | curve equation is modified to: | |
77 | ||
78 | y^2 + xy = x^3 + ax^2 + b (where b != 0) | |
79 | ||
80 | Operations in a binary field are performed relative to an | |
81 | B<irreducible polynomial>. All such curves with OpenSSL use a trinomial or a | |
82 | pentanomial for this parameter. | |
83 | ||
84 | Although deprecated since OpenSSL 3.0 and should no longer be used, | |
85 | a new curve can be constructed by calling EC_GROUP_new(), using the | |
86 | implementation provided by B<meth> (see L<EC_GFp_simple_method(3)>) and | |
87 | associated with the library context B<ctx> (see L<OPENSSL_CTX(3)>). | |
88 | The B<ctx> parameter may be NULL in which case the default library context is | |
89 | used. | |
90 | It is then necessary to call EC_GROUP_set_curve() to set the curve parameters. | |
91 | Applications should instead use one of the other EC_GROUP_new_* constructors. | |
92 | ||
93 | EC_GROUP_new_from_ecparameters() will create a group from the | |
94 | specified B<params> and | |
95 | EC_GROUP_new_from_ecpkparameters() will create a group from the specific PK | |
96 | B<params>. | |
97 | ||
98 | EC_GROUP_set_curve() sets the curve parameters B<p>, B<a> and B<b>. For a curve | |
99 | over Fp B<p> is the prime for the field. For a curve over F2^m B<p> represents | |
100 | the irreducible polynomial - each bit represents a term in the polynomial. | |
101 | Therefore there will either be three or five bits set dependent on whether the | |
102 | polynomial is a trinomial or a pentanomial. | |
103 | In either case, B<a> and B<b> represents the coefficients a and b from the | |
104 | relevant equation introduced above. | |
105 | ||
106 | EC_group_get_curve() obtains the previously set curve parameters. | |
107 | ||
108 | EC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for | |
109 | EC_GROUP_set_curve(). They are defined for backwards compatibility only and | |
110 | should not be used. | |
111 | ||
112 | EC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for | |
113 | EC_GROUP_get_curve(). They are defined for backwards compatibility only and | |
114 | should not be used. | |
115 | ||
116 | The functions EC_GROUP_new_curve_GFp() and EC_GROUP_new_curve_GF2m() are | |
117 | shortcuts for calling EC_GROUP_new() and then the EC_GROUP_set_curve() function. | |
118 | An appropriate default implementation method will be used. | |
119 | ||
120 | Whilst the library can be used to create any curve using the functions described | |
121 | above, there are also a number of predefined curves that are available. In order | |
122 | to obtain a list of all of the predefined curves, call the function | |
123 | EC_get_builtin_curves(). The parameter B<r> should be an array of | |
124 | EC_builtin_curve structures of size B<nitems>. The function will populate the | |
125 | B<r> array with information about the built-in curves. If B<nitems> is less than | |
126 | the total number of curves available, then the first B<nitems> curves will be | |
127 | returned. Otherwise the total number of curves will be provided. The return | |
128 | value is the total number of curves available (whether that number has been | |
129 | populated in B<r> or not). Passing a NULL B<r>, or setting B<nitems> to 0 will | |
130 | do nothing other than return the total number of curves available. | |
131 | The EC_builtin_curve structure is defined as follows: | |
132 | ||
133 | typedef struct { | |
134 | int nid; | |
135 | const char *comment; | |
136 | } EC_builtin_curve; | |
137 | ||
138 | Each EC_builtin_curve item has a unique integer id (B<nid>), and a human | |
139 | readable comment string describing the curve. | |
140 | ||
141 | In order to construct a built-in curve use the function | |
142 | EC_GROUP_new_by_curve_name_ex() and provide the B<nid> of the curve to be | |
143 | constructed and the associated library context to be used in B<ctx> (see | |
144 | L<OPENSSL_CTX(3)>). The B<ctx> value may be NULL in which case the default | |
145 | library context is used. | |
146 | ||
147 | EC_GROUP_new_by_curve_name() is the same as EC_GROUP_new_by_curve_name_ex() | |
148 | except that the default library context is always used. | |
149 | ||
150 | EC_GROUP_free() frees the memory associated with the EC_GROUP. | |
151 | If B<group> is NULL nothing is done. | |
152 | ||
153 | EC_GROUP_clear_free() is deprecated: it was meant to destroy any sensitive data | |
154 | held within the EC_GROUP and then free its memory, but since all the data stored | |
155 | in the EC_GROUP is public anyway, this function is unnecessary. | |
156 | Its use can be safely replaced with EC_GROUP_free(). | |
157 | If B<group> is NULL nothing is done. | |
158 | ||
159 | =head1 RETURN VALUES | |
160 | ||
161 | All EC_GROUP_new* functions return a pointer to the newly constructed group, or | |
162 | NULL on error. | |
163 | ||
164 | EC_get_builtin_curves() returns the number of built-in curves that are | |
165 | available. | |
166 | ||
167 | EC_GROUP_set_curve_GFp(), EC_GROUP_get_curve_GFp(), EC_GROUP_set_curve_GF2m(), | |
168 | EC_GROUP_get_curve_GF2m() return 1 on success or 0 on error. | |
169 | ||
170 | =head1 SEE ALSO | |
171 | ||
172 | L<crypto(7)>, L<EC_GROUP_copy(3)>, | |
173 | L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>, | |
174 | L<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>, | |
175 | L<OPENSSL_CTX(3)> | |
176 | ||
177 | =head1 HISTORY | |
178 | ||
179 | =over 2 | |
180 | ||
181 | =item * | |
182 | ||
183 | EC_GROUP_new() was deprecated in OpenSSL 3.0. | |
184 | ||
185 | EC_GROUP_new_by_curve_name_ex() was added in OpenSSL 3.0. | |
186 | ||
187 | =item * | |
188 | ||
189 | EC_GROUP_clear_free() was deprecated in OpenSSL 3.0; use EC_GROUP_free() | |
190 | instead. | |
191 | ||
192 | =back | |
193 | ||
194 | =head1 COPYRIGHT | |
195 | ||
196 | Copyright 2013-2020 The OpenSSL Project Authors. All Rights Reserved. | |
197 | ||
198 | Licensed under the Apache License 2.0 (the "License"). You may not use | |
199 | this file except in compliance with the License. You can obtain a copy | |
200 | in the file LICENSE in the source distribution or at | |
201 | L<https://www.openssl.org/source/license.html>. | |
202 | ||
203 | =cut |