EC_POINT_new.pod 13 KB

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  1. =pod
  2. =head1 NAME
  3. EC_POINT_set_Jprojective_coordinates_GFp,
  4. EC_POINT_point2buf,
  5. EC_POINT_new,
  6. EC_POINT_free,
  7. EC_POINT_clear_free,
  8. EC_POINT_copy,
  9. EC_POINT_dup,
  10. EC_POINT_method_of,
  11. EC_POINT_set_to_infinity,
  12. EC_POINT_get_Jprojective_coordinates_GFp,
  13. EC_POINT_set_affine_coordinates,
  14. EC_POINT_get_affine_coordinates,
  15. EC_POINT_set_compressed_coordinates,
  16. EC_POINT_set_affine_coordinates_GFp,
  17. EC_POINT_get_affine_coordinates_GFp,
  18. EC_POINT_set_compressed_coordinates_GFp,
  19. EC_POINT_set_affine_coordinates_GF2m,
  20. EC_POINT_get_affine_coordinates_GF2m,
  21. EC_POINT_set_compressed_coordinates_GF2m,
  22. EC_POINT_point2oct,
  23. EC_POINT_oct2point,
  24. EC_POINT_point2bn,
  25. EC_POINT_bn2point,
  26. EC_POINT_point2hex,
  27. EC_POINT_hex2point
  28. - Functions for creating, destroying and manipulating EC_POINT objects
  29. =head1 SYNOPSIS
  30. #include <openssl/ec.h>
  31. EC_POINT *EC_POINT_new(const EC_GROUP *group);
  32. void EC_POINT_free(EC_POINT *point);
  33. void EC_POINT_clear_free(EC_POINT *point);
  34. int EC_POINT_copy(EC_POINT *dst, const EC_POINT *src);
  35. EC_POINT *EC_POINT_dup(const EC_POINT *src, const EC_GROUP *group);
  36. int EC_POINT_set_to_infinity(const EC_GROUP *group, EC_POINT *point);
  37. int EC_POINT_set_affine_coordinates(const EC_GROUP *group, EC_POINT *p,
  38. const BIGNUM *x, const BIGNUM *y,
  39. BN_CTX *ctx);
  40. int EC_POINT_get_affine_coordinates(const EC_GROUP *group, const EC_POINT *p,
  41. BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
  42. int EC_POINT_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *p,
  43. const BIGNUM *x, int y_bit,
  44. BN_CTX *ctx);
  45. size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *p,
  46. point_conversion_form_t form,
  47. unsigned char *buf, size_t len, BN_CTX *ctx);
  48. size_t EC_POINT_point2buf(const EC_GROUP *group, const EC_POINT *point,
  49. point_conversion_form_t form,
  50. unsigned char **pbuf, BN_CTX *ctx);
  51. int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *p,
  52. const unsigned char *buf, size_t len, BN_CTX *ctx);
  53. BIGNUM *EC_POINT_point2bn(const EC_GROUP *group, const EC_POINT *p,
  54. point_conversion_form_t form, BIGNUM *bn,
  55. BN_CTX *ctx);
  56. EC_POINT *EC_POINT_bn2point(const EC_GROUP *group, const BIGNUM *bn,
  57. EC_POINT *p, BN_CTX *ctx);
  58. char *EC_POINT_point2hex(const EC_GROUP *group, const EC_POINT *p,
  59. point_conversion_form_t form, BN_CTX *ctx);
  60. EC_POINT *EC_POINT_hex2point(const EC_GROUP *group, const char *hex,
  61. EC_POINT *p, BN_CTX *ctx);
  62. Deprecated since OpenSSL 3.0:
  63. const EC_METHOD *EC_POINT_method_of(const EC_POINT *point);
  64. int EC_POINT_set_Jprojective_coordinates_GFp(const EC_GROUP *group,
  65. EC_POINT *p,
  66. const BIGNUM *x, const BIGNUM *y,
  67. const BIGNUM *z, BN_CTX *ctx);
  68. int EC_POINT_get_Jprojective_coordinates_GFp(const EC_GROUP *group,
  69. const EC_POINT *p,
  70. BIGNUM *x, BIGNUM *y, BIGNUM *z,
  71. BN_CTX *ctx);
  72. int EC_POINT_set_affine_coordinates_GFp(const EC_GROUP *group, EC_POINT *p,
  73. const BIGNUM *x, const BIGNUM *y,
  74. BN_CTX *ctx);
  75. int EC_POINT_get_affine_coordinates_GFp(const EC_GROUP *group,
  76. const EC_POINT *p,
  77. BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
  78. int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group,
  79. EC_POINT *p,
  80. const BIGNUM *x, int y_bit,
  81. BN_CTX *ctx);
  82. int EC_POINT_set_affine_coordinates_GF2m(const EC_GROUP *group, EC_POINT *p,
  83. const BIGNUM *x, const BIGNUM *y,
  84. BN_CTX *ctx);
  85. int EC_POINT_get_affine_coordinates_GF2m(const EC_GROUP *group,
  86. const EC_POINT *p,
  87. BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
  88. int EC_POINT_set_compressed_coordinates_GF2m(const EC_GROUP *group,
  89. EC_POINT *p,
  90. const BIGNUM *x, int y_bit,
  91. BN_CTX *ctx);
  92. =head1 DESCRIPTION
  93. An B<EC_POINT> structure represents a point on a curve. A new point is
  94. constructed by calling the function EC_POINT_new() and providing the
  95. B<group> object that the point relates to.
  96. EC_POINT_free() frees the memory associated with the B<EC_POINT>.
  97. if B<point> is NULL nothing is done.
  98. EC_POINT_clear_free() destroys any sensitive data held within the EC_POINT and
  99. then frees its memory. If B<point> is NULL nothing is done.
  100. EC_POINT_copy() copies the point B<src> into B<dst>. Both B<src> and B<dst>
  101. must use the same B<EC_METHOD>.
  102. EC_POINT_dup() creates a new B<EC_POINT> object and copies the content from
  103. B<src> to the newly created B<EC_POINT> object.
  104. EC_POINT_method_of() obtains the B<EC_METHOD> associated with B<point>.
  105. This function was deprecated in OpenSSL 3.0, since EC_METHOD is no longer a
  106. public concept.
  107. A valid point on a curve is the special point at infinity. A point is set to
  108. be at infinity by calling EC_POINT_set_to_infinity().
  109. The affine co-ordinates for a point describe a point in terms of its x and y
  110. position. The function EC_POINT_set_affine_coordinates() sets the B<x> and B<y>
  111. co-ordinates for the point B<p> defined over the curve given in B<group>. The
  112. function EC_POINT_get_affine_coordinates() sets B<x> and B<y>, either of which
  113. may be NULL, to the corresponding coordinates of B<p>.
  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 compatibility
  117. only and should not be used.
  118. The functions EC_POINT_get_affine_coordinates_GFp() and
  119. EC_POINT_get_affine_coordinates_GF2m() are synonyms for
  120. EC_POINT_get_affine_coordinates(). They are defined for backwards compatibility
  121. only and should not be used.
  122. As well as the affine co-ordinates, a point can alternatively be described in
  123. terms of its Jacobian projective co-ordinates (for Fp curves only). Jacobian
  124. projective co-ordinates are expressed as three values x, y and z. Working in
  125. this co-ordinate system provides more efficient point multiplication
  126. operations. A mapping exists between Jacobian projective co-ordinates and
  127. affine co-ordinates. A Jacobian projective co-ordinate (x, y, z) can be written
  128. as an affine co-ordinate as (x/(z^2), y/(z^3)). Conversion to Jacobian
  129. projective from affine co-ordinates is simple. The co-ordinate (x, y) is mapped
  130. to (x, y, 1). Although deprecated in OpenSSL 3.0 and should no longer be used,
  131. to set or get the projective co-ordinates in older versions use
  132. EC_POINT_set_Jprojective_coordinates_GFp() and
  133. EC_POINT_get_Jprojective_coordinates_GFp() respectively.
  134. Modern versions should instead use EC_POINT_set_affine_coordinates() and
  135. EC_POINT_get_affine_coordinates(), performing the conversion manually using the
  136. above maps in such rare circumstances.
  137. Points can also be described in terms of their compressed co-ordinates. For a
  138. point (x, y), for any given value for x such that the point is on the curve
  139. there will only ever be two possible values for y. Therefore, a point can be set
  140. using the EC_POINT_set_compressed_coordinates() function where B<x> is the x
  141. co-ordinate and B<y_bit> is a value 0 or 1 to identify which of the two
  142. possible values for y should be used.
  143. The functions EC_POINT_set_compressed_coordinates_GFp() and
  144. EC_POINT_set_compressed_coordinates_GF2m() are synonyms for
  145. EC_POINT_set_compressed_coordinates(). They are defined for backwards
  146. compatibility only and should not be used.
  147. In addition B<EC_POINT> can be converted to and from various external
  148. representations. The octet form is the binary encoding of the B<ECPoint>
  149. structure (as defined in RFC5480 and used in certificates and TLS records):
  150. only the content octets are present, the B<OCTET STRING> tag and length are
  151. not included. B<BIGNUM> form is the octet form interpreted as a big endian
  152. integer converted to a B<BIGNUM> structure. Hexadecimal form is the octet
  153. form converted to a NULL terminated character string where each character
  154. is one of the printable values 0-9 or A-F (or a-f).
  155. The functions EC_POINT_point2oct(), EC_POINT_oct2point(), EC_POINT_point2bn(),
  156. EC_POINT_bn2point(), EC_POINT_point2hex() and EC_POINT_hex2point() convert from
  157. and to EC_POINTs for the formats: octet, BIGNUM and hexadecimal respectively.
  158. The function EC_POINT_point2oct() encodes the given curve point B<p> as an
  159. octet string into the buffer B<buf> of size B<len>, using the specified
  160. conversion form B<form>.
  161. The encoding conforms with Sec. 2.3.3 of the SECG SEC 1 ("Elliptic Curve
  162. Cryptography") standard.
  163. Similarly the function EC_POINT_oct2point() decodes a curve point into B<p> from
  164. the octet string contained in the given buffer B<buf> of size B<len>, conforming
  165. to Sec. 2.3.4 of the SECG SEC 1 ("Elliptic Curve Cryptography") standard.
  166. The functions EC_POINT_point2hex() and EC_POINT_point2bn() convert a point B<p>,
  167. respectively, to the hexadecimal or BIGNUM representation of the same
  168. encoding of the function EC_POINT_point2oct().
  169. Vice versa, similarly to the function EC_POINT_oct2point(), the functions
  170. EC_POINT_hex2point() and EC_POINT_point2bn() decode the hexadecimal or
  171. BIGNUM representation into the EC_POINT B<p>.
  172. Notice that, according to the standard, the octet string encoding of the point
  173. at infinity for a given curve is fixed to a single octet of value zero and that,
  174. vice versa, a single octet of size zero is decoded as the point at infinity.
  175. The function EC_POINT_point2oct() must be supplied with a buffer long enough to
  176. store the octet form. The return value provides the number of octets stored.
  177. Calling the function with a NULL buffer will not perform the conversion but
  178. will still return the required buffer length.
  179. The function EC_POINT_point2buf() allocates a buffer of suitable length and
  180. writes an EC_POINT to it in octet format. The allocated buffer is written to
  181. B<*pbuf> and its length is returned. The caller must free up the allocated
  182. buffer with a call to OPENSSL_free(). Since the allocated buffer value is
  183. written to B<*pbuf> the B<pbuf> parameter B<MUST NOT> be B<NULL>.
  184. The function EC_POINT_point2hex() will allocate sufficient memory to store the
  185. hexadecimal string. It is the caller's responsibility to free this memory with
  186. a subsequent call to OPENSSL_free().
  187. =head1 RETURN VALUES
  188. EC_POINT_new() and EC_POINT_dup() return the newly allocated EC_POINT or NULL
  189. on error.
  190. The following functions return 1 on success or 0 on error: EC_POINT_copy(),
  191. EC_POINT_set_to_infinity(), EC_POINT_set_Jprojective_coordinates_GFp(),
  192. EC_POINT_get_Jprojective_coordinates_GFp(),
  193. EC_POINT_set_affine_coordinates_GFp(), EC_POINT_get_affine_coordinates_GFp(),
  194. EC_POINT_set_compressed_coordinates_GFp(),
  195. EC_POINT_set_affine_coordinates_GF2m(), EC_POINT_get_affine_coordinates_GF2m(),
  196. EC_POINT_set_compressed_coordinates_GF2m() and EC_POINT_oct2point().
  197. EC_POINT_method_of returns the EC_METHOD associated with the supplied EC_POINT.
  198. EC_POINT_point2oct() and EC_POINT_point2buf() return the length of the required
  199. buffer or 0 on error.
  200. EC_POINT_point2bn() returns the pointer to the BIGNUM supplied, or NULL on
  201. error.
  202. EC_POINT_bn2point() returns the pointer to the EC_POINT supplied, or NULL on
  203. error.
  204. EC_POINT_point2hex() returns a pointer to the hex string, or NULL on error.
  205. EC_POINT_hex2point() returns the pointer to the EC_POINT supplied, or NULL on
  206. error.
  207. =head1 SEE ALSO
  208. L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>,
  209. L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
  210. L<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>
  211. =head1 HISTORY
  212. EC_POINT_method_of(),
  213. EC_POINT_set_Jprojective_coordinates_GFp(),
  214. EC_POINT_get_Jprojective_coordinates_GFp(),
  215. EC_POINT_set_affine_coordinates_GFp(), EC_POINT_get_affine_coordinates_GFp(),
  216. EC_POINT_set_compressed_coordinates_GFp(),
  217. EC_POINT_set_affine_coordinates_GF2m(), EC_POINT_get_affine_coordinates_GF2m(),
  218. EC_POINT_set_compressed_coordinates_GF2m() were deprecated in OpenSSL 3.0.
  219. B<EC_POINT_set_affine_coordinates>, B<EC_POINT_get_affine_coordinates>,
  220. and B<EC_POINT_set_compressed_coordinates> were
  221. added in OpenSSL 1.1.1.
  222. =head1 COPYRIGHT
  223. Copyright 2013-2020 The OpenSSL Project Authors. All Rights Reserved.
  224. Licensed under the Apache License 2.0 (the "License"). You may not use
  225. this file except in compliance with the License. You can obtain a copy
  226. in the file LICENSE in the source distribution or at
  227. L<https://www.openssl.org/source/license.html>.
  228. =cut