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Title "EC_POINT_NEW 3"
way too many mistakes in technical documents.
The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):
.Vb 10 const EC_METHOD *EC_POINT_method_of(const 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); 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); .Ve
\fBEC_POINT_free() frees the memory associated with the \s-1EC_POINT\s0. if point is \s-1NULL\s0 nothing is done.
\fBEC_POINT_clear_free() destroys any sensitive data held within the \s-1EC_POINT\s0 and then frees its memory. If point is \s-1NULL\s0 nothing is done.
\fBEC_POINT_copy() copies the point src into dst. Both src and dst must use the same \s-1EC_METHOD\s0.
\fBEC_POINT_dup() creates a new \s-1EC_POINT\s0 object and copies the content from \fBsrc to the newly created \s-1EC_POINT\s0 object.
\fBEC_POINT_method_of() obtains the \s-1EC_METHOD\s0 associated with point. This function was deprecated in OpenSSL 3.0, since \s-1EC_METHOD\s0 is no longer a public concept.
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 coordinates for a point describe a point in terms of its x and y position. The function EC_POINT_set_affine_coordinates() sets the x and y coordinates for the point p defined over the curve given in group. The function EC_POINT_get_affine_coordinates() sets x and y, either of which may be \s-1NULL,\s0 to the corresponding coordinates of p.
The functions EC_POINT_set_affine_coordinates_GFp() and \fBEC_POINT_set_affine_coordinates_GF2m() are synonyms for \fBEC_POINT_set_affine_coordinates(). They are defined for backwards compatibility only and should not be used.
The functions EC_POINT_get_affine_coordinates_GFp() and \fBEC_POINT_get_affine_coordinates_GF2m() are synonyms for \fBEC_POINT_get_affine_coordinates(). They are defined for backwards compatibility only and should not be used.
As well as the affine coordinates, a point can alternatively be described in terms of its Jacobian projective coordinates (for Fp curves only). Jacobian projective coordinates are expressed as three values x, y and z. Working in this coordinate system provides more efficient point multiplication operations. A mapping exists between Jacobian projective coordinates and affine coordinates. A Jacobian projective coordinate (x, y, z) can be written as an affine coordinate as (x/(z^2), y/(z^3)). Conversion to Jacobian projective from affine coordinates is simple. The coordinate (x, y) is mapped to (x, y, 1). Although deprecated in OpenSSL 3.0 and should no longer be used, to set or get the projective coordinates in older versions use \fBEC_POINT_set_Jprojective_coordinates_GFp() and \fBEC_POINT_get_Jprojective_coordinates_GFp() respectively. Modern versions should instead use EC_POINT_set_affine_coordinates() and \fBEC_POINT_get_affine_coordinates(), performing the conversion manually using the above maps in such rare circumstances.
Points can also be described in terms of their compressed coordinates. 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() function where x is the x coordinate and y_bit is a value 0 or 1 to identify which of the two possible values for y should be used.
The functions EC_POINT_set_compressed_coordinates_GFp() and \fBEC_POINT_set_compressed_coordinates_GF2m() are synonyms for \fBEC_POINT_set_compressed_coordinates(). They are defined for backwards compatibility only and should not be used.
In addition \s-1EC_POINT\s0 can be converted to and from various external representations. The octet form is the binary encoding of the ECPoint structure (as defined in \s-1RFC5480\s0 and used in certificates and \s-1TLS\s0 records): only the content octets are present, the \s-1OCTET STRING\s0 tag and length are not included. \s-1BIGNUM\s0 form is the octet form interpreted as a big endian integer converted to a \s-1BIGNUM\s0 structure. Hexadecimal form is the octet form converted to a \s-1NULL\s0 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(), \fBEC_POINT_bn2point(), EC_POINT_point2hex() and EC_POINT_hex2point() convert from and to EC_POINTs for the formats: octet, \s-1BIGNUM\s0 and hexadecimal respectively.
The function EC_POINT_point2oct() encodes the given curve point p as an octet string into the buffer buf of size len, using the specified conversion form form. The encoding conforms with Sec. 2.3.3 of the \s-1SECG SEC 1\s0 (\*(L"Elliptic Curve Cryptography\*(R") standard. Similarly the function EC_POINT_oct2point() decodes a curve point into p from the octet string contained in the given buffer buf of size len, conforming to Sec. 2.3.4 of the \s-1SECG SEC 1\s0 (\*(L"Elliptic Curve Cryptography\*(R") standard.
The functions EC_POINT_point2hex() and EC_POINT_point2bn() convert a point p, respectively, to the hexadecimal or \s-1BIGNUM\s0 representation of the same encoding of the function EC_POINT_point2oct(). Vice versa, similarly to the function EC_POINT_oct2point(), the functions \fBEC_POINT_hex2point() and EC_POINT_point2bn() decode the hexadecimal or \s-1BIGNUM\s0 representation into the \s-1EC_POINT\s0 p.
Notice that, according to the standard, the octet string encoding of the point at infinity for a given curve is fixed to a single octet of value zero and that, vice versa, a single octet of size zero is decoded as the point at infinity.
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 \s-1NULL\s0 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 \s-1EC_POINT\s0 to it in octet format. The allocated buffer is written to \fB*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 *pbuf the pbuf parameter \s-1MUST NOT\s0 be \s-1NULL\s0.
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().
The following functions return 1 on success or 0 on error: EC_POINT_copy(), \fBEC_POINT_set_to_infinity(), EC_POINT_set_Jprojective_coordinates_GFp(), \fBEC_POINT_get_Jprojective_coordinates_GFp(), \fBEC_POINT_set_affine_coordinates_GFp(), EC_POINT_get_affine_coordinates_GFp(), \fBEC_POINT_set_compressed_coordinates_GFp(), \fBEC_POINT_set_affine_coordinates_GF2m(), EC_POINT_get_affine_coordinates_GF2m(), \fBEC_POINT_set_compressed_coordinates_GF2m() and EC_POINT_oct2point().
EC_POINT_method_of returns the \s-1EC_METHOD\s0 associated with the supplied \s-1EC_POINT.\s0
\fBEC_POINT_point2oct() and EC_POINT_point2buf() return the length of the required buffer or 0 on error.
\fBEC_POINT_point2bn() returns the pointer to the \s-1BIGNUM\s0 supplied, or \s-1NULL\s0 on error.
\fBEC_POINT_bn2point() returns the pointer to the \s-1EC_POINT\s0 supplied, or \s-1NULL\s0 on error.
\fBEC_POINT_point2hex() returns a pointer to the hex string, or \s-1NULL\s0 on error.
\fBEC_POINT_hex2point() returns the pointer to the \s-1EC_POINT\s0 supplied, or \s-1NULL\s0 on error.
\fBEC_POINT_set_affine_coordinates, EC_POINT_get_affine_coordinates, and EC_POINT_set_compressed_coordinates were added in OpenSSL 1.1.1.
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.