From: Dr. Stephen Henson Date: Sat, 27 Feb 2016 00:16:23 +0000 (+0000) Subject: Update and clarify EC_POINT documentation. X-Git-Tag: OpenSSL_1_1_0-pre4~486 X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=43986596c672eb5dd20c363f12fef09a04cdc9e5 Update and clarify EC_POINT documentation. 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 --- diff --git a/doc/crypto/EC_POINT_new.pod b/doc/crypto/EC_POINT_new.pod index 122dccb975..8e11f0b1be 100644 --- a/doc/crypto/EC_POINT_new.pod +++ b/doc/crypto/EC_POINT_new.pod @@ -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 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 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); + 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 *); + 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 EC_POINT 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. +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 EC_POINT. +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 EC_METHOD. - -EC_POINT_dup creates a new EC_POINT object and copies the content from B to the newly created -EC_POINT object. - -EC_POINT_method_of obtains the EC_METHOD 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 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 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 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 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(). +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 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 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. +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