EC_POINT_new.pod 9.7 KB

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  1. =pod
  2. =head1 NAME
  3. EC_POINT_set_Jprojective_coordinates_GFp, EC_POINT_point2buf,
  4. EC_POINT_new, EC_POINT_free, EC_POINT_clear_free,
  5. EC_POINT_copy, EC_POINT_dup, EC_POINT_method_of,
  6. EC_POINT_set_to_infinity,
  7. EC_POINT_get_Jprojective_coordinates_GFp,
  8. EC_POINT_set_affine_coordinates_GFp,
  9. EC_POINT_get_affine_coordinates_GFp, EC_POINT_set_compressed_coordinates_GFp,
  10. EC_POINT_set_affine_coordinates_GF2m, EC_POINT_get_affine_coordinates_GF2m,
  11. EC_POINT_set_compressed_coordinates_GF2m, EC_POINT_point2oct,
  12. EC_POINT_oct2point, EC_POINT_point2bn, EC_POINT_bn2point, EC_POINT_point2hex,
  13. EC_POINT_hex2point
  14. - Functions for creating, destroying and manipulating EC_POINT objects
  15. =head1 SYNOPSIS
  16. #include <openssl/ec.h>
  17. EC_POINT *EC_POINT_new(const EC_GROUP *group);
  18. void EC_POINT_free(EC_POINT *point);
  19. void EC_POINT_clear_free(EC_POINT *point);
  20. int EC_POINT_copy(EC_POINT *dst, const EC_POINT *src);
  21. EC_POINT *EC_POINT_dup(const EC_POINT *src, const EC_GROUP *group);
  22. const EC_METHOD *EC_POINT_method_of(const EC_POINT *point);
  23. int EC_POINT_set_to_infinity(const EC_GROUP *group, EC_POINT *point);
  24. int EC_POINT_set_Jprojective_coordinates_GFp(const EC_GROUP *group,
  25. EC_POINT *p,
  26. const BIGNUM *x, const BIGNUM *y,
  27. const BIGNUM *z, BN_CTX *ctx);
  28. int EC_POINT_get_Jprojective_coordinates_GFp(const EC_GROUP *group,
  29. const EC_POINT *p,
  30. BIGNUM *x, BIGNUM *y, BIGNUM *z,
  31. BN_CTX *ctx);
  32. int EC_POINT_set_affine_coordinates_GFp(const EC_GROUP *group, EC_POINT *p,
  33. const BIGNUM *x, const BIGNUM *y,
  34. BN_CTX *ctx);
  35. int EC_POINT_get_affine_coordinates_GFp(const EC_GROUP *group,
  36. const EC_POINT *p,
  37. BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
  38. int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group,
  39. EC_POINT *p,
  40. const BIGNUM *x, int y_bit,
  41. BN_CTX *ctx);
  42. int EC_POINT_set_affine_coordinates_GF2m(const EC_GROUP *group, EC_POINT *p,
  43. const BIGNUM *x, const BIGNUM *y,
  44. BN_CTX *ctx);
  45. int EC_POINT_get_affine_coordinates_GF2m(const EC_GROUP *group,
  46. const EC_POINT *p,
  47. BIGNUM *x, BIGNUM *y, BN_CTX *ctx);
  48. int EC_POINT_set_compressed_coordinates_GF2m(const EC_GROUP *group,
  49. EC_POINT *p,
  50. const BIGNUM *x, int y_bit,
  51. BN_CTX *ctx);
  52. size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *p,
  53. point_conversion_form_t form,
  54. unsigned char *buf, size_t len, BN_CTX *ctx);
  55. size_t EC_POINT_point2buf(const EC_GROUP *group, const EC_POINT *point,
  56. point_conversion_form_t form,
  57. unsigned char **pbuf, BN_CTX *ctx);
  58. int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *p,
  59. const unsigned char *buf, size_t len, BN_CTX *ctx);
  60. BIGNUM *EC_POINT_point2bn(const EC_GROUP *group, const EC_POINT *p,
  61. point_conversion_form_t form, BIGNUM *bn,
  62. BN_CTX *ctx);
  63. EC_POINT *EC_POINT_bn2point(const EC_GROUP *group, const BIGNUM *bn,
  64. EC_POINT *p, BN_CTX *ctx);
  65. char *EC_POINT_point2hex(const EC_GROUP *group, const EC_POINT *p,
  66. point_conversion_form_t form, BN_CTX *ctx);
  67. EC_POINT *EC_POINT_hex2point(const EC_GROUP *group, const char *hex,
  68. EC_POINT *p, BN_CTX *ctx);
  69. =head1 DESCRIPTION
  70. An B<EC_POINT> structure represents a point on a curve. A new point is
  71. constructed by calling the function EC_POINT_new() and providing the
  72. B<group> object that the point relates to.
  73. EC_POINT_free() frees the memory associated with the B<EC_POINT>.
  74. if B<point> is NULL nothing is done.
  75. EC_POINT_clear_free() destroys any sensitive data held within the EC_POINT and
  76. then frees its memory. If B<point> is NULL nothing is done.
  77. EC_POINT_copy() copies the point B<src> into B<dst>. Both B<src> and B<dst>
  78. must use the same B<EC_METHOD>.
  79. EC_POINT_dup() creates a new B<EC_POINT> object and copies the content from
  80. B<src> to the newly created B<EC_POINT> object.
  81. EC_POINT_method_of() obtains the B<EC_METHOD> associated with B<point>.
  82. A valid point on a curve is the special point at infinity. A point is set to
  83. be at infinity by calling EC_POINT_set_to_infinity().
  84. The affine co-ordinates for a point describe a point in terms of its x and y
  85. position. The functions EC_POINT_set_affine_coordinates_GFp() and
  86. EC_POINT_set_affine_coordinates_GF2m() set the B<x> and B<y> co-ordinates for
  87. the point B<p> defined over the curve given in B<group>. The functions
  88. EC_POINT_get_affine_coordinates_GFp() and
  89. EC_POINT_get_affine_coordinates_GF2m() set B<x> and B<y>, either of which may
  90. be NULL, to the corresponding coordinates of B<p>.
  91. As well as the affine co-ordinates, a point can alternatively be described in
  92. terms of its Jacobian projective co-ordinates (for Fp curves only). Jacobian
  93. projective co-ordinates are expressed as three values x, y and z. Working in
  94. this co-ordinate system provides more efficient point multiplication
  95. operations. A mapping exists between Jacobian projective co-ordinates and
  96. affine co-ordinates. A Jacobian projective co-ordinate (x, y, z) can be written
  97. as an affine co-ordinate as (x/(z^2), y/(z^3)). Conversion to Jacobian
  98. projective from affine co-ordinates is simple. The co-ordinate (x, y) is mapped
  99. to (x, y, 1). To set or get the projective co-ordinates use
  100. EC_POINT_set_Jprojective_coordinates_GFp() and
  101. EC_POINT_get_Jprojective_coordinates_GFp() respectively.
  102. Points can also be described in terms of their compressed co-ordinates. For a
  103. point (x, y), for any given value for x such that the point is on the curve
  104. there will only ever be two possible values for y. Therefore a point can be set
  105. using the EC_POINT_set_compressed_coordinates_GFp() and
  106. EC_POINT_set_compressed_coordinates_GF2m() functions where B<x> is the x
  107. co-ordinate and B<y_bit> is a value 0 or 1 to identify which of the two
  108. possible values for y should be used.
  109. In addition B<EC_POINT> can be converted to and from various external
  110. representations. The octet form is the binary encoding of the B<ECPoint>
  111. structure (as defined in RFC5480 and used in certificates and TLS records):
  112. only the content octets are present, the B<OCTET STRING> tag and length are
  113. not included. B<BIGNUM> form is the octet form interpreted as a big endian
  114. integer converted to a B<BIGNUM> structure. Hexadecimal form is the octet
  115. form converted to a NULL terminated character string where each character
  116. is one of the printable values 0-9 or A-F (or a-f).
  117. The functions EC_POINT_point2oct(), EC_POINT_oct2point(), EC_POINT_point2bn(),
  118. EC_POINT_bn2point(), EC_POINT_point2hex() and EC_POINT_hex2point() convert from
  119. and to EC_POINTs for the formats: octet, BIGNUM and hexadecimal respectively.
  120. The function EC_POINT_point2oct() must be supplied with a buffer long enough to
  121. store the octet form. The return value provides the number of octets stored.
  122. Calling the function with a NULL buffer will not perform the conversion but
  123. will still return the required buffer length.
  124. The function EC_POINT_point2buf() allocates a buffer of suitable length and
  125. writes an EC_POINT to it in octet format. The allocated buffer is written to
  126. B<*pbuf> and its length is returned. The caller must free up the allocated
  127. buffer with a call to OPENSSL_free(). Since the allocated buffer value is
  128. written to B<*pbuf> the B<pbuf> parameter B<MUST NOT> be B<NULL>.
  129. The function EC_POINT_point2hex() will allocate sufficient memory to store the
  130. hexadecimal string. It is the caller's responsibility to free this memory with
  131. a subsequent call to OPENSSL_free().
  132. =head1 RETURN VALUES
  133. EC_POINT_new() and EC_POINT_dup() return the newly allocated EC_POINT or NULL
  134. on error.
  135. The following functions return 1 on success or 0 on error: EC_POINT_copy(),
  136. EC_POINT_set_to_infinity(), EC_POINT_set_Jprojective_coordinates_GFp(),
  137. EC_POINT_get_Jprojective_coordinates_GFp(),
  138. EC_POINT_set_affine_coordinates_GFp(), EC_POINT_get_affine_coordinates_GFp(),
  139. EC_POINT_set_compressed_coordinates_GFp(),
  140. EC_POINT_set_affine_coordinates_GF2m(), EC_POINT_get_affine_coordinates_GF2m(),
  141. EC_POINT_set_compressed_coordinates_GF2m() and EC_POINT_oct2point().
  142. EC_POINT_method_of returns the EC_METHOD associated with the supplied EC_POINT.
  143. EC_POINT_point2oct() and EC_POINT_point2buf() return the length of the required
  144. buffer or 0 on error.
  145. EC_POINT_point2bn() returns the pointer to the BIGNUM supplied, or NULL on
  146. error.
  147. EC_POINT_bn2point() returns the pointer to the EC_POINT supplied, or NULL on
  148. error.
  149. EC_POINT_point2hex() returns a pointer to the hex string, or NULL on error.
  150. EC_POINT_hex2point() returns the pointer to the EC_POINT supplied, or NULL on
  151. error.
  152. =head1 SEE ALSO
  153. L<crypto(7)>, L<EC_GROUP_new(3)>, L<EC_GROUP_copy(3)>,
  154. L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
  155. L<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>
  156. =head1 COPYRIGHT
  157. Copyright 2013-2018 The OpenSSL Project Authors. All Rights Reserved.
  158. Licensed under the OpenSSL license (the "License"). You may not use
  159. this file except in compliance with the License. You can obtain a copy
  160. in the file LICENSE in the source distribution or at
  161. L<https://www.openssl.org/source/license.html>.
  162. =cut