EC_POINT_point2bn(3)

NAME

       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_set_Jprojective_coordinates, EC_POINT_get_Jprojective_coordi-
       nates_GFp, EC_POINT_set_affine_coordinates_GFp,
       EC_POINT_get_affine_coordinates_GFp, EC_POINT_set_compressed_coordi-
       nates_GFp, EC_POINT_set_affine_coordinates_GF2m,
       EC_POINT_get_affine_coordinates_GF2m, EC_POINT_set_compressed_coordi-
       nates_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.

SYNOPSIS

        #include <openssl/ec.h>
        #include <openssl/bn.h>

        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);
        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 *, const EC_POINT *,
               point_conversion_form_t form, BIGNUM *, BN_CTX *);
        EC_POINT *EC_POINT_bn2point(const EC_GROUP *, const BIGNUM *,
               EC_POINT *, BN_CTX *);
        char *EC_POINT_point2hex(const EC_GROUP *, const EC_POINT *,
               point_conversion_form_t form, BN_CTX *);
        EC_POINT *EC_POINT_hex2point(const EC_GROUP *, const char *,
               EC_POINT *, BN_CTX *);

DESCRIPTION

       An EC_POINT represents a point on a curve. A new point is constructed
       by calling the function EC_POINT_new and providing the group object
       that the point relates to.

       EC_POINT_free frees the memory associated with the EC_POINT.

       EC_POINT_clear_free destroys any sensitive data held within the
       EC_POINT and then frees its memory.

       EC_POINT_copy copies the point src into dst. Both src and dst must use
       the same EC_METHOD.

       EC_POINT_dup creates a new EC_POINT object and copies the content from
       src to the newly created EC_POINT object.

       EC_POINT_method_of obtains the EC_METHOD associated with point.

       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 x and y co-ordinates for
       the point p defined over the curve given in group.

       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-ordi-
       nate as (x/(z^2), y/(z^3)). Conversion to Jacobian projective to 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_Jprojec-
       tive_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 x is the x
       co-ordinate and y_bit is a value 0 or 1 to identify which of the two
       possible values for y should be used.

       In addition EC_POINTs can be converted to and from various external
       representations. Supported representations are octet strings, BIGNUMs
       and hexadecimal. Octet strings are stored in a buffer along with an
       associated buffer length. A point held in a BIGNUM is calculated by
       converting the point to an octet string and then converting that octet
       string into a BIGNUM integer.  Points in hexadecimal format are stored
       in 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
       string, BIGNUM and hexadecimal respectively.

       The function EC_POINT_point2oct must be supplied with a buffer long
       enough to store the octet string. The return value provides the number
       of octets stored. Calling the function with a NULL buffer will not per-
       form the conversion but will still return the required buffer length.

       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().

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_coor-
       dinates_GFp, EC_POINT_get_Jprojective_coordinates_GFp,
       EC_POINT_set_affine_coordinates_GFp, EC_POINT_get_affine_coordi-
       nates_GFp, EC_POINT_set_compressed_coordinates_GFp,
       EC_POINT_set_affine_coordinates_GF2m, EC_POINT_get_affine_coordi-
       nates_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 returns 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.

EC_POINT_point2bn(3)

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUES

SEE ALSO