=pod =head1 NAME EC_POINT_set_Jprojective_coordinates_GFp, EC_POINT_point2buf, EC_POINT_new, EC_POINT_free, EC_POINT_clear_free, EC_POINT_copy, EC_POINT_dup, EC_POINT_method_of, EC_POINT_set_to_infinity, EC_POINT_get_Jprojective_coordinates_GFp, EC_POINT_set_affine_coordinates_GFp, EC_POINT_get_affine_coordinates_GFp, EC_POINT_set_compressed_coordinates_GFp, EC_POINT_set_affine_coordinates_GF2m, EC_POINT_get_affine_coordinates_GF2m, EC_POINT_set_compressed_coordinates_GF2m, EC_POINT_point2oct, EC_POINT_oct2point, EC_POINT_point2bn, EC_POINT_bn2point, EC_POINT_point2hex, EC_POINT_hex2point - Functions for creating, destroying and manipulating EC_POINT objects =head1 SYNOPSIS #include EC_POINT *EC_POINT_new(const EC_GROUP *group); void EC_POINT_free(EC_POINT *point); void EC_POINT_clear_free(EC_POINT *point); int EC_POINT_copy(EC_POINT *dst, const EC_POINT *src); EC_POINT *EC_POINT_dup(const EC_POINT *src, const EC_GROUP *group); const EC_METHOD *EC_POINT_method_of(const EC_POINT *point); int EC_POINT_set_to_infinity(const EC_GROUP *group, EC_POINT *point); int EC_POINT_set_Jprojective_coordinates_GFp(const EC_GROUP *group, EC_POINT *p, const BIGNUM *x, const BIGNUM *y, const BIGNUM *z, BN_CTX *ctx); int EC_POINT_get_Jprojective_coordinates_GFp(const EC_GROUP *group, const EC_POINT *p, BIGNUM *x, BIGNUM *y, BIGNUM *z, BN_CTX *ctx); int EC_POINT_set_affine_coordinates_GFp(const EC_GROUP *group, EC_POINT *p, const BIGNUM *x, const BIGNUM *y, BN_CTX *ctx); int EC_POINT_get_affine_coordinates_GFp(const EC_GROUP *group, const EC_POINT *p, BIGNUM *x, BIGNUM *y, BN_CTX *ctx); int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group, EC_POINT *p, const BIGNUM *x, int y_bit, BN_CTX *ctx); int EC_POINT_set_affine_coordinates_GF2m(const EC_GROUP *group, EC_POINT *p, const BIGNUM *x, const BIGNUM *y, BN_CTX *ctx); int EC_POINT_get_affine_coordinates_GF2m(const EC_GROUP *group, const EC_POINT *p, BIGNUM *x, BIGNUM *y, BN_CTX *ctx); int EC_POINT_set_compressed_coordinates_GF2m(const EC_GROUP *group, EC_POINT *p, const BIGNUM *x, int y_bit, BN_CTX *ctx); size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *p, point_conversion_form_t form, unsigned char *buf, size_t len, BN_CTX *ctx); size_t EC_POINT_point2buf(const EC_GROUP *group, const EC_POINT *point, point_conversion_form_t form, unsigned char **pbuf, BN_CTX *ctx); int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *p, const unsigned char *buf, size_t len, BN_CTX *ctx); BIGNUM *EC_POINT_point2bn(const EC_GROUP *group, const EC_POINT *p, point_conversion_form_t form, BIGNUM *bn, BN_CTX *ctx); EC_POINT *EC_POINT_bn2point(const EC_GROUP *group, const BIGNUM *bn, EC_POINT *p, BN_CTX *ctx); char *EC_POINT_point2hex(const EC_GROUP *group, const EC_POINT *p, point_conversion_form_t form, BN_CTX *ctx); EC_POINT *EC_POINT_hex2point(const EC_GROUP *group, const char *hex, EC_POINT *p, BN_CTX *ctx); =head1 DESCRIPTION An B structure represents a point on a curve. A new point is constructed by calling the function EC_POINT_new() and providing the B object that the point relates to. EC_POINT_free() frees the memory associated with the B. if B is NULL nothing is done. EC_POINT_clear_free() destroys any sensitive data held within the EC_POINT and then frees its memory. If B is NULL nothing is done. EC_POINT_copy() copies the point B into B. Both B and B must use the same B. EC_POINT_dup() creates a new B object and copies the content from B to the newly created B object. EC_POINT_method_of() obtains the B associated with B. A valid point on a curve is the special point at infinity. A point is set to be at infinity by calling EC_POINT_set_to_infinity(). The affine co-ordinates for a point describe a point in terms of its x and y position. The functions EC_POINT_set_affine_coordinates_GFp() and EC_POINT_set_affine_coordinates_GF2m() set the B and B co-ordinates for the point B

defined over the curve given in B. As well as the affine co-ordinates, a point can alternatively be described in terms of its Jacobian projective co-ordinates (for Fp curves only). Jacobian projective co-ordinates are expressed as three values x, y and z. Working in this co-ordinate system provides more efficient point multiplication operations. A mapping exists between Jacobian projective co-ordinates and affine co-ordinates. A Jacobian projective co-ordinate (x, y, z) can be written as an affine co-ordinate as (x/(z^2), y/(z^3)). Conversion to Jacobian projective from affine co-ordinates is simple. The co-ordinate (x, y) is mapped to (x, y, 1). To set or get the projective co-ordinates use EC_POINT_set_Jprojective_coordinates_GFp() and EC_POINT_get_Jprojective_coordinates_GFp() respectively. Points can also be described in terms of their compressed co-ordinates. For a point (x, y), for any given value for x such that the point is on the curve there will only ever be two possible values for y. Therefore a point can be set using the EC_POINT_set_compressed_coordinates_GFp() and EC_POINT_set_compressed_coordinates_GF2m() functions where B is the x co-ordinate and B is a value 0 or 1 to identify which of the two possible values for y should be used. In addition B can be converted to and from various external representations. The octet form is the binary encoding of the B structure (as defined in RFC5480 and used in certificates and TLS records): only the content octets are present, the B tag and length are not included. B form is the octet form interpreted as a big endian integer converted to a B structure. Hexadecimal form is the octet form converted to a NULL terminated character string where each character is one of the printable values 0-9 or A-F (or a-f). The functions EC_POINT_point2oct(), EC_POINT_oct2point(), EC_POINT_point2bn(), EC_POINT_bn2point(), EC_POINT_point2hex() and EC_POINT_hex2point() convert from and to EC_POINTs for the formats: octet, BIGNUM and hexadecimal respectively. The function EC_POINT_point2oct() must be supplied with a buffer long enough to store the octet form. The return value provides the number of octets stored. Calling the function with a NULL buffer will not perform the conversion but will still return the required buffer length. The function EC_POINT_point2buf() allocates a buffer of suitable length and writes an EC_POINT to it in octet format. The allocated buffer is written to B<*pbuf> and its length is returned. The caller must free up the allocated buffer with a call to OPENSSL_free(). Since the allocated buffer value is written to B<*pbuf> the B parameter B be B. The function EC_POINT_point2hex() will allocate sufficient memory to store the hexadecimal string. It is the caller's responsibility to free this memory with a subsequent call to OPENSSL_free(). =head1 RETURN VALUES EC_POINT_new() and EC_POINT_dup() return the newly allocated EC_POINT or NULL on error. The following functions return 1 on success or 0 on error: EC_POINT_copy(), EC_POINT_set_to_infinity(), EC_POINT_set_Jprojective_coordinates_GFp(), EC_POINT_get_Jprojective_coordinates_GFp(), EC_POINT_set_affine_coordinates_GFp(), EC_POINT_get_affine_coordinates_GFp(), EC_POINT_set_compressed_coordinates_GFp(), EC_POINT_set_affine_coordinates_GF2m(), EC_POINT_get_affine_coordinates_GF2m(), EC_POINT_set_compressed_coordinates_GF2m() and EC_POINT_oct2point(). EC_POINT_method_of returns the EC_METHOD associated with the supplied EC_POINT. EC_POINT_point2oct() and EC_point2buf() return the length of the required buffer or 0 on error. EC_POINT_point2bn() returns the pointer to the BIGNUM supplied, or NULL on error. EC_POINT_bn2point() returns the pointer to the EC_POINT supplied, or NULL on error. EC_POINT_point2hex() returns a pointer to the hex string, or NULL on error. EC_POINT_hex2point() returns the pointer to the EC_POINT supplied, or NULL on error. =head1 SEE ALSO L, L, L, L, L, L, L =head1 COPYRIGHT Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut