← Back
Editing: EC_POINT_method_of.3
.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). .\" Fear. Run. Save yourself. No user-serviceable parts. . \" fudge factors for nroff and troff .if n \{\ . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] \fP .\} .if t \{\ . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff .if n \{\ . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} .if t \{\ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' .ds 8 \h'\*(#H'\(*b\h'-\*(#H' .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] .ds ae a\h'-(\w'a'u*4/10)'e .ds Ae A\h'-(\w'A'u*4/10)'E . \" corrections for vroff .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' . \" for low resolution devices (crt and lpr) .if \n(.H>23 .if \n(.V>19 \ \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} .rm #[ #] #H #V #F C .\" ======================================================================== .\" .IX Title "EC_POINT_new 3" .TH EC_POINT_new 3 "2019-12-20" "1.0.2u" "OpenSSL" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 EC_POINT objects. .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 2 \& #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 *); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" An \s-1EC_POINT\s0 represents a point on a curve. A new point is constructed by calling the function EC_POINT_new and providing the \fBgroup\fR object that the point relates to. .PP EC_POINT_free frees the memory associated with the \s-1EC_POINT.\s0 .PP EC_POINT_clear_free destroys any sensitive data held within the \s-1EC_POINT\s0 and then frees its memory. .PP EC_POINT_copy copies the point \fBsrc\fR into \fBdst\fR. Both \fBsrc\fR and \fBdst\fR must use the same \s-1EC_METHOD.\s0 .PP EC_POINT_dup creates a new \s-1EC_POINT\s0 object and copies the content from \fBsrc\fR to the newly created \&\s-1EC_POINT\s0 object. .PP EC_POINT_method_of obtains the \s-1EC_METHOD\s0 associated with \fBpoint\fR. .PP 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. .PP 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 \fBx\fR and \fBy\fR co-ordinates for the point \&\fBp\fR defined over the curve given in \fBgroup\fR. .PP 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. .PP 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 \fBx\fR is the x co-ordinate and \fBy_bit\fR is a value 0 or 1 to identify which of the two possible values for y should be used. .PP 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 \s-1BIGNUM\s0 is calculated by converting the point to an octet string and then converting that octet string into a \s-1BIGNUM\s0 integer. Points in hexadecimal format are stored in a \s-1NULL\s0 terminated character string where each character is one of the printable values 0\-9 or A\-F (or a\-f). .PP 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, \s-1BIGNUM\s0 and hexadecimal respectively. .PP 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 \s-1NULL\s0 buffer will not perform the conversion but will still return the required buffer length. .PP 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 \fBOPENSSL_free()\fR. .SH "RETURN VALUES" .IX Header "RETURN VALUES" EC_POINT_new and EC_POINT_dup return the newly allocated \s-1EC_POINT\s0 or \s-1NULL\s0 on error. .PP 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. .PP EC_POINT_method_of returns the \s-1EC_METHOD\s0 associated with the supplied \s-1EC_POINT.\s0 .PP EC_POINT_point2oct returns the length of the required buffer, or 0 on error. .PP EC_POINT_point2bn returns the pointer to the \s-1BIGNUM\s0 supplied, or \s-1NULL\s0 on error. .PP EC_POINT_bn2point returns the pointer to the \s-1EC_POINT\s0 supplied, or \s-1NULL\s0 on error. .PP EC_POINT_point2hex returns a pointer to the hex string, or \s-1NULL\s0 on error. .PP EC_POINT_hex2point returns the pointer to the \s-1EC_POINT\s0 supplied, or \s-1NULL\s0 on error. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBcrypto\fR\|(3), \fBec\fR\|(3), \fBEC_GROUP_new\fR\|(3), \fBEC_GROUP_copy\fR\|(3), \&\fBEC_POINT_add\fR\|(3), \fBEC_KEY_new\fR\|(3), \&\fBEC_GFp_simple_method\fR\|(3), \fBd2i_ECPKParameters\fR\|(3)
Save File
Cancel