generic-library/openssl
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Update and clarify EC_POINT documentation.

Browse Source 
Reformat EC_POINT_new.pod and add parentheses to function names.
Clarify the octet form.
Add documentation for EC_POINT_oct2buf().

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Dr. Stephen Henson 2016-02-27 00:16:23 +00:00
parent 766579ec89
commit 43986596c6
1 changed files with 124 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

187
doc/crypto/EC_POINT_new.pod
View File

@ -2,7 +2,15 @@
=head1 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_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 B<EC_POINT> objects.
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_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 B<EC_POINT> objects.
=head1 SYNOPSIS
@ -16,110 +24,157 @@ EC_POINT_new, EC_POINT_free, EC_POINT_clear_free, EC_POINT_copy, EC_POINT_dup, E
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_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);
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);
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);
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);
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);
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 *, 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 *);
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 EC_POINT represents a point on a curve. A new point is constructed by calling the function EC_POINT_new and providing the B<group>
object that the point relates to.
An B<EC_POINT> structure represents a point on a curve. A new point is
constructed by calling the function EC_POINT_new() and providing the
B<group> object that the point relates to.
EC_POINT_free frees the memory associated with the EC_POINT.
EC_POINT_free() frees the memory associated with the B<EC_POINT>.
if B<point> 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<point> 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<point> is NULL nothing is done.
EC_POINT_copy copies the point B<src> into B<dst>. Both B<src> and B<dst> must use the same EC_METHOD.
EC_POINT_copy() copies the point B<src> into B<dst>. Both B<src> and B<dst>
must use the same B<EC_METHOD>.
EC_POINT_dup creates a new EC_POINT object and copies the content from B<src> to the newly created
EC_POINT object.
EC_POINT_dup() creates a new B<EC_POINT> object and copies the content from
B<src> to the newly created B<EC_POINT> object.
EC_POINT_method_of obtains the EC_METHOD associated with B<point>.
EC_POINT_method_of() obtains the B<EC_METHOD> associated with B<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.
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<x> and B<y> co-ordinates for the point
B<p> defined over the curve given in B<group>.
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<x> and B<y> co-ordinates for
the point B<p> defined over the curve given in B<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-ordinate 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_Jprojective_coordinates_GFp and
EC_POINT_get_Jprojective_coordinates_GFp respectively.
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 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_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<x> is the x co-ordinate and B<y_bit> is a value 0 or 1 to identify which of
the two possible values for y should be used.
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<x> is the x
co-ordinate and B<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).
In addition B<EC_POINT> can be converted to and from various external
representations. The octet form is the binary encoding of the B<ECPoint>
structure (as defined in RFC5480 and used in certificates and TLS records):
only the content octets are present, the B<OCTET STRING> tag and length are
not included. B<BIGNUM> form is the octet form interpreted as a big endian
integer converted to a B<BIGNUM> 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 string, BIGNUM and hexadecimal respectively.
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 string. 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_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_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 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<pbuf> parameter B<MUST NOT> be B<NULL>.
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.
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.
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 returns the length of the required buffer, or 0 on error.
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_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_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_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_hex2point() returns the pointer to the EC_POINT supplied, or NULL on
error.
=head1 SEE ALSO