1EC_POINT_NEW(3)                     OpenSSL                    EC_POINT_NEW(3)
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NAME

6       EC_POINT_set_Jprojective_coordinates_GFp, EC_POINT_point2buf,
7       EC_POINT_new, EC_POINT_free, EC_POINT_clear_free, EC_POINT_copy,
8       EC_POINT_dup, EC_POINT_method_of, EC_POINT_set_to_infinity,
9       EC_POINT_get_Jprojective_coordinates_GFp,
10       EC_POINT_set_affine_coordinates, EC_POINT_get_affine_coordinates,
11       EC_POINT_set_compressed_coordinates,
12       EC_POINT_set_affine_coordinates_GFp,
13       EC_POINT_get_affine_coordinates_GFp,
14       EC_POINT_set_compressed_coordinates_GFp,
15       EC_POINT_set_affine_coordinates_GF2m,
16       EC_POINT_get_affine_coordinates_GF2m,
17       EC_POINT_set_compressed_coordinates_GF2m, EC_POINT_point2oct,
18       EC_POINT_oct2point, EC_POINT_point2bn, EC_POINT_bn2point,
19       EC_POINT_point2hex, EC_POINT_hex2point - Functions for creating,
20       destroying and manipulating EC_POINT objects
21

SYNOPSIS

23        #include <openssl/ec.h>
24
25        EC_POINT *EC_POINT_new(const EC_GROUP *group);
26        void EC_POINT_free(EC_POINT *point);
27        void EC_POINT_clear_free(EC_POINT *point);
28        int EC_POINT_copy(EC_POINT *dst, const EC_POINT *src);
29        EC_POINT *EC_POINT_dup(const EC_POINT *src, const EC_GROUP *group);
30        const EC_METHOD *EC_POINT_method_of(const EC_POINT *point);
31        int EC_POINT_set_to_infinity(const EC_GROUP *group, EC_POINT *point);
32        int EC_POINT_set_Jprojective_coordinates_GFp(const EC_GROUP *group,
33                                                     EC_POINT *p,
34                                                     const BIGNUM *x, const BIGNUM *y,
35                                                     const BIGNUM *z, BN_CTX *ctx);
36        int EC_POINT_get_Jprojective_coordinates_GFp(const EC_GROUP *group,
37                                                     const EC_POINT *p,
38                                                     BIGNUM *x, BIGNUM *y, BIGNUM *z,
39                                                     BN_CTX *ctx);
40        int EC_POINT_set_affine_coordinates(const EC_GROUP *group, EC_POINT *p,
41                                            const BIGNUM *x, const BIGNUM *y,
42                                            BN_CTX *ctx);
43        int EC_POINT_get_affine_coordinates(const EC_GROUP *group, const EC_POINT *p,
44                                            BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
45        int EC_POINT_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *p,
46                                                const BIGNUM *x, int y_bit,
47                                                BN_CTX *ctx);
48        int EC_POINT_set_affine_coordinates_GFp(const EC_GROUP *group, EC_POINT *p,
49                                                const BIGNUM *x, const BIGNUM *y,
50                                                BN_CTX *ctx);
51        int EC_POINT_get_affine_coordinates_GFp(const EC_GROUP *group,
52                                                const EC_POINT *p,
53                                                BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
54        int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group,
55                                                    EC_POINT *p,
56                                                    const BIGNUM *x, int y_bit,
57                                                    BN_CTX *ctx);
58        int EC_POINT_set_affine_coordinates_GF2m(const EC_GROUP *group, EC_POINT *p,
59                                                 const BIGNUM *x, const BIGNUM *y,
60                                                 BN_CTX *ctx);
61        int EC_POINT_get_affine_coordinates_GF2m(const EC_GROUP *group,
62                                                 const EC_POINT *p,
63                                                 BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
64        int EC_POINT_set_compressed_coordinates_GF2m(const EC_GROUP *group,
65                                                     EC_POINT *p,
66                                                     const BIGNUM *x, int y_bit,
67                                                     BN_CTX *ctx);
68        size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *p,
69                                  point_conversion_form_t form,
70                                  unsigned char *buf, size_t len, BN_CTX *ctx);
71        size_t EC_POINT_point2buf(const EC_GROUP *group, const EC_POINT *point,
72                                  point_conversion_form_t form,
73                                  unsigned char **pbuf, BN_CTX *ctx);
74        int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *p,
75                               const unsigned char *buf, size_t len, BN_CTX *ctx);
76        BIGNUM *EC_POINT_point2bn(const EC_GROUP *group, const EC_POINT *p,
77                                  point_conversion_form_t form, BIGNUM *bn,
78                                  BN_CTX *ctx);
79        EC_POINT *EC_POINT_bn2point(const EC_GROUP *group, const BIGNUM *bn,
80                                    EC_POINT *p, BN_CTX *ctx);
81        char *EC_POINT_point2hex(const EC_GROUP *group, const EC_POINT *p,
82                                 point_conversion_form_t form, BN_CTX *ctx);
83        EC_POINT *EC_POINT_hex2point(const EC_GROUP *group, const char *hex,
84                                     EC_POINT *p, BN_CTX *ctx);
85

DESCRIPTION

87       An EC_POINT structure represents a point on a curve. A new point is
88       constructed by calling the function EC_POINT_new() and providing the
89       group object that the point relates to.
90
91       EC_POINT_free() frees the memory associated with the EC_POINT.  if
92       point is NULL nothing is done.
93
94       EC_POINT_clear_free() destroys any sensitive data held within the
95       EC_POINT and then frees its memory. If point is NULL nothing is done.
96
97       EC_POINT_copy() copies the point src into dst. Both src and dst must
98       use the same EC_METHOD.
99
100       EC_POINT_dup() creates a new EC_POINT object and copies the content
101       from src to the newly created EC_POINT object.
102
103       EC_POINT_method_of() obtains the EC_METHOD associated with point.
104
105       A valid point on a curve is the special point at infinity. A point is
106       set to be at infinity by calling EC_POINT_set_to_infinity().
107
108       The affine co-ordinates for a point describe a point in terms of its x
109       and y position. The function EC_POINT_set_affine_coordinates() sets the
110       x and y co-ordinates for the point p defined over the curve given in
111       group. The function EC_POINT_get_affine_coordinates() sets x and y,
112       either of which may be NULL, to the corresponding coordinates of p.
113
114       The functions EC_POINT_set_affine_coordinates_GFp() and
115       EC_POINT_set_affine_coordinates_GF2m() are synonyms for
116       EC_POINT_set_affine_coordinates(). They are defined for backwards
117       compatibility only and should not be used.
118
119       The functions EC_POINT_get_affine_coordinates_GFp() and
120       EC_POINT_get_affine_coordinates_GF2m() are synonyms for
121       EC_POINT_get_affine_coordinates(). They are defined for backwards
122       compatibility only and should not be used.
123
124       As well as the affine co-ordinates, a point can alternatively be
125       described in terms of its Jacobian projective co-ordinates (for Fp
126       curves only). Jacobian projective co-ordinates are expressed as three
127       values x, y and z. Working in this co-ordinate system provides more
128       efficient point multiplication operations.  A mapping exists between
129       Jacobian projective co-ordinates and affine co-ordinates. A Jacobian
130       projective co-ordinate (x, y, z) can be written as an affine co-
131       ordinate as (x/(z^2), y/(z^3)). Conversion to Jacobian projective from
132       affine co-ordinates is simple. The co-ordinate (x, y) is mapped to (x,
133       y, 1). To set or get the projective co-ordinates use
134       EC_POINT_set_Jprojective_coordinates_GFp() and
135       EC_POINT_get_Jprojective_coordinates_GFp() respectively.
136
137       Points can also be described in terms of their compressed co-ordinates.
138       For a point (x, y), for any given value for x such that the point is on
139       the curve there will only ever be two possible values for y. Therefore,
140       a point can be set using the EC_POINT_set_compressed_coordinates()
141       function where x is the x co-ordinate and y_bit is a value 0 or 1 to
142       identify which of the two possible values for y should be used.
143
144       The functions EC_POINT_set_compressed_coordinates_GFp() and
145       EC_POINT_set_compressed_coordinates_GF2m() are synonyms for
146       EC_POINT_set_compressed_coordinates(). They are defined for backwards
147       compatibility only and should not be used.
148
149       In addition EC_POINT can be converted to and from various external
150       representations. The octet form is the binary encoding of the ECPoint
151       structure (as defined in RFC5480 and used in certificates and TLS
152       records): only the content octets are present, the OCTET STRING tag and
153       length are not included. BIGNUM form is the octet form interpreted as a
154       big endian integer converted to a BIGNUM structure. Hexadecimal form is
155       the octet form converted to a NULL terminated character string where
156       each character is one of the printable values 0-9 or A-F (or a-f).
157
158       The functions EC_POINT_point2oct(), EC_POINT_oct2point(),
159       EC_POINT_point2bn(), EC_POINT_bn2point(), EC_POINT_point2hex() and
160       EC_POINT_hex2point() convert from and to EC_POINTs for the formats:
161       octet, BIGNUM and hexadecimal respectively.
162
163       The function EC_POINT_point2oct() encodes the given curve point p as an
164       octet string into the buffer buf of size len, using the specified
165       conversion form form.  The encoding conforms with Sec. 2.3.3 of the
166       SECG SEC 1 ("Elliptic Curve Cryptography") standard.  Similarly the
167       function EC_POINT_oct2point() decodes a curve point into p from the
168       octet string contained in the given buffer buf of size len, conforming
169       to Sec. 2.3.4 of the SECG SEC 1 ("Elliptic Curve Cryptography")
170       standard.
171
172       The functions EC_POINT_point2hex() and EC_POINT_point2bn() convert a
173       point p, respectively, to the hexadecimal or BIGNUM representation of
174       the same encoding of the function EC_POINT_point2oct().  Vice versa,
175       similarly to the function EC_POINT_oct2point(), the functions
176       EC_POINT_hex2point() and EC_POINT_point2bn() decode the hexadecimal or
177       BIGNUM representation into the EC_POINT p.
178
179       Notice that, according to the standard, the octet string encoding of
180       the point at infinity for a given curve is fixed to a single octet of
181       value zero and that, vice versa, a single octet of size zero is decoded
182       as the point at infinity.
183
184       The function EC_POINT_point2oct() must be supplied with a buffer long
185       enough to store the octet form. The return value provides the number of
186       octets stored.  Calling the function with a NULL buffer will not
187       perform the conversion but will still return the required buffer
188       length.
189
190       The function EC_POINT_point2buf() allocates a buffer of suitable length
191       and writes an EC_POINT to it in octet format. The allocated buffer is
192       written to *pbuf and its length is returned. The caller must free up
193       the allocated buffer with a call to OPENSSL_free(). Since the allocated
194       buffer value is written to *pbuf the pbuf parameter MUST NOT be NULL.
195
196       The function EC_POINT_point2hex() will allocate sufficient memory to
197       store the hexadecimal string. It is the caller's responsibility to free
198       this memory with a subsequent call to OPENSSL_free().
199

RETURN VALUES

201       EC_POINT_new() and EC_POINT_dup() return the newly allocated EC_POINT
202       or NULL on error.
203
204       The following functions return 1 on success or 0 on error:
205       EC_POINT_copy(), EC_POINT_set_to_infinity(),
206       EC_POINT_set_Jprojective_coordinates_GFp(),
207       EC_POINT_get_Jprojective_coordinates_GFp(),
208       EC_POINT_set_affine_coordinates_GFp(),
209       EC_POINT_get_affine_coordinates_GFp(),
210       EC_POINT_set_compressed_coordinates_GFp(),
211       EC_POINT_set_affine_coordinates_GF2m(),
212       EC_POINT_get_affine_coordinates_GF2m(),
213       EC_POINT_set_compressed_coordinates_GF2m() and EC_POINT_oct2point().
214
215       EC_POINT_method_of returns the EC_METHOD associated with the supplied
216       EC_POINT.
217
218       EC_POINT_point2oct() and EC_POINT_point2buf() return the length of the
219       required buffer or 0 on error.
220
221       EC_POINT_point2bn() returns the pointer to the BIGNUM supplied, or NULL
222       on error.
223
224       EC_POINT_bn2point() returns the pointer to the EC_POINT supplied, or
225       NULL on error.
226
227       EC_POINT_point2hex() returns a pointer to the hex string, or NULL on
228       error.
229
230       EC_POINT_hex2point() returns the pointer to the EC_POINT supplied, or
231       NULL on error.
232

SEE ALSO

234       crypto(7), EC_GROUP_new(3), EC_GROUP_copy(3), EC_POINT_add(3),
235       EC_KEY_new(3), EC_GFp_simple_method(3), d2i_ECPKParameters(3)
236
238       Copyright 2013-2020 The OpenSSL Project Authors. All Rights Reserved.
239
240       Licensed under the OpenSSL license (the "License").  You may not use
241       this file except in compliance with the License.  You can obtain a copy
242       in the file LICENSE in the source distribution or at
243       <https://www.openssl.org/source/license.html>.
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2471.1.1l                            2021-09-15                   EC_POINT_NEW(3)
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