EC_POINT_ADD(3)

NAME
EC_POINT_add, EC_POINT_dbl, EC_POINT_invert, EC_POINT_is_at_infinity, EC_POINT_is_on_curve, EC_POINT_cmp, EC_POINT_make_affine, EC_POINTs_make_affine, EC_POINTs_mul, EC_POINT_mul, EC_GROUP_precompute_mult, EC_GROUP_have_precompute_mult - perform mathematical operations and tests on EC_POINT objects

SYNOPSIS
#include <openssl/ec.h>
#include <openssl/bn.h>
int
EC_POINT_add(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a, const EC_POINT *b, BN_CTX *ctx);
int
EC_POINT_dbl(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a, BN_CTX *ctx);
int
EC_POINT_invert(const EC_GROUP *group, EC_POINT *a, BN_CTX *ctx);
int
EC_POINT_is_at_infinity(const EC_GROUP *group, const EC_POINT *p);
int
EC_POINT_is_on_curve(const EC_GROUP *group, const EC_POINT *point, BN_CTX *ctx);
int
EC_POINT_cmp(const EC_GROUP *group, const EC_POINT *a, const EC_POINT *b, BN_CTX *ctx);
int
EC_POINT_make_affine(const EC_GROUP *group, EC_POINT *point, BN_CTX *ctx);
int
EC_POINTs_make_affine(const EC_GROUP *group, size_t num, EC_POINT *points[], BN_CTX *ctx);
int
EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *n, size_t num, const EC_POINT *p[], const BIGNUM *m[], BN_CTX *ctx);
int
EC_POINT_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *n, const EC_POINT *q, const BIGNUM *m, BN_CTX *ctx);
int
EC_GROUP_precompute_mult(EC_GROUP *group, BN_CTX *ctx);
int
EC_GROUP_have_precompute_mult(const EC_GROUP *group);

DESCRIPTION
These functions operate on EC_POINT objects created by EC_POINT_new(3).

EC_POINT_add() adds the two points a and b and places the result in r. Similarly EC_POINT_dbl() doubles the point a and places the result in r. In both cases it is valid for r to be one of a or b.

EC_POINT_invert() calculates the inverse of the supplied point a. The result is placed back in a.

The function EC_POINT_is_at_infinity() tests whether the supplied point is at infinity or not.

EC_POINT_is_on_curve() tests whether the supplied point is on the curve or not.

EC_POINT_cmp() compares the two supplied points and tests whether or not they are equal.

The functions EC_POINT_make_affine() and EC_POINTs_make_affine() force the internal representation of the EC_POINTs into the affine coordinate system. In the case of EC_POINTs_make_affine(), the value num provides the number of points in the array points to be forced.

EC_POINT_mul() calculates the value

    generator * n + q * m

and stores the result in r. The value n may be NULL, in which case the result is just

    q * m.

EC_POINTs_mul() only supports the values 0 and 1 for num. If it is 1, then EC_POINTs_mul() calculates the value

    generator * n + q[0] * m[0].

If num is 0 then q and m must be NULL, and the result is just

    generator * n.

As for EC_POINT_mul(), the value n may be NULL.

The function EC_GROUP_precompute_mult() stores multiples of the generator for faster point multiplication, whilst EC_GROUP_have_precompute_mult() tests whether precomputation has already been done. See EC_GROUP_copy(3) for information about the generator.

RETURN VALUES
The following functions return 1 on success or 0 on error: EC_POINT_add(), EC_POINT_dbl(), EC_POINT_invert(), EC_POINT_make_affine(), EC_POINTs_make_affine(), EC_POINT_mul(), EC_POINTs_mul(), and EC_GROUP_precompute_mult().

EC_POINT_is_at_infinity() returns 1 if the point is at infinity or 0 otherwise.

EC_POINT_is_on_curve() returns 1 if the point is on the curve, 0 if not, or -1 on error.

EC_POINT_cmp() returns 1 if the points are not equal, 0 if they are, or -1 on error.

EC_GROUP_have_precompute_mult() returns 1 if a precomputation has been done or 0 if not.

SEE ALSO
d2i_ECPKParameters(3), EC_GFp_simple_method(3), EC_GROUP_copy(3), EC_GROUP_new(3), EC_KEY_new(3), EC_POINT_new(3)

HISTORY
EC_POINT_add(), EC_POINT_dbl(), EC_POINT_invert(), EC_POINT_is_at_infinity(), EC_POINT_is_on_curve(), EC_POINT_cmp(), EC_POINT_make_affine(), EC_POINTs_make_affine(), EC_POINTs_mul(), EC_POINT_mul(), and EC_GROUP_precompute_mult() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

EC_GROUP_have_precompute_mult() first appeared in OpenSSL 0.9.8 and has been available since OpenBSD 4.5.