22

✏️ Editing: ECDSA_sign_ex.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 "ECDSA_SIG_NEW 3"
.TH ECDSA_SIG_NEW 3 "2023-09-11" "1.1.1w" "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"
ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0, ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_size, ECDSA_sign, ECDSA_do_sign, ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex, ECDSA_do_sign_ex \- low\-level elliptic curve digital signature algorithm (ECDSA) functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ecdsa.h>
\&
\& ECDSA_SIG *ECDSA_SIG_new(void);
\& void ECDSA_SIG_free(ECDSA_SIG *sig);
\& void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
\& const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
\& const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
\& int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);
\& int ECDSA_size(const EC_KEY *eckey);
\&
\& int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen,
\&                unsigned char *sig, unsigned int *siglen, EC_KEY *eckey);
\& ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
\&                          EC_KEY *eckey);
\&
\& int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen,
\&                  const unsigned char *sig, int siglen, EC_KEY *eckey);
\& int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
\&                     const ECDSA_SIG *sig, EC_KEY* eckey);
\&
\& ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
\&                             const BIGNUM *kinv, const BIGNUM *rp,
\&                             EC_KEY *eckey);
\& int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp);
\& int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen,
\&                   unsigned char *sig, unsigned int *siglen,
\&                   const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Note: these functions provide a low-level interface to \s-1ECDSA.\s0 Most
applications should use the higher level \fB\s-1EVP\s0\fR interface such as
\&\fBEVP_DigestSignInit\fR\|(3) or \fBEVP_DigestVerifyInit\fR\|(3) instead.
.PP
\&\fB\s-1ECDSA_SIG\s0\fR is an opaque structure consisting of two BIGNUMs for the
\&\fBr\fR and \fBs\fR value of an \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS 186\-2\s0).
.PP
\&\fBECDSA_SIG_new()\fR allocates an empty \fB\s-1ECDSA_SIG\s0\fR structure. Note: before
OpenSSL 1.1.0 the: the \fBr\fR and \fBs\fR components were initialised.
.PP
\&\fBECDSA_SIG_free()\fR frees the \fB\s-1ECDSA_SIG\s0\fR structure \fBsig\fR.
.PP
\&\fBECDSA_SIG_get0()\fR returns internal pointers the \fBr\fR and \fBs\fR values contained
in \fBsig\fR and stores them in \fB*pr\fR and \fB*ps\fR, respectively.
The pointer \fBpr\fR or \fBps\fR can be \s-1NULL,\s0 in which case the corresponding value
is not returned.
.PP
The values \fBr\fR, \fBs\fR can also be retrieved separately by the corresponding
function \fBECDSA_SIG_get0_r()\fR and \fBECDSA_SIG_get0_s()\fR, respectively.
.PP
The \fBr\fR and \fBs\fR values can be set by calling \fBECDSA_SIG_set0()\fR and passing the
new values for \fBr\fR and \fBs\fR as parameters to the function. Calling this
function transfers the memory management of the values to the \s-1ECDSA_SIG\s0 object,
and therefore the values that have been passed in should not be freed directly
after this function has been called.
.PP
See \fBi2d_ECDSA_SIG\fR\|(3) and \fBd2i_ECDSA_SIG\fR\|(3) for information about encoding
and decoding \s-1ECDSA\s0 signatures to/from \s-1DER.\s0
.PP
\&\fBECDSA_size()\fR returns the maximum length of a \s-1DER\s0 encoded \s-1ECDSA\s0 signature
created with the private \s-1EC\s0 key \fBeckey\fR.
.PP
\&\fBECDSA_sign()\fR computes a digital signature of the \fBdgstlen\fR bytes hash value
\&\fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR. The \s-1DER\s0 encoded signatures is
stored in \fBsig\fR and its length is returned in \fBsig_len\fR. Note: \fBsig\fR must
point to ECDSA_size(eckey) bytes of memory. The parameter \fBtype\fR is currently
ignored. \fBECDSA_sign()\fR is wrapper function for \fBECDSA_sign_ex()\fR with \fBkinv\fR
and \fBrp\fR set to \s-1NULL.\s0
.PP
\&\fBECDSA_do_sign()\fR is similar to \fBECDSA_sign()\fR except the signature is returned
as a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error). \fBECDSA_do_sign()\fR
is a wrapper function for \fBECDSA_do_sign_ex()\fR with \fBkinv\fR and \fBrp\fR set to
\&\s-1NULL.\s0
.PP
\&\fBECDSA_verify()\fR verifies that the signature in \fBsig\fR of size \fBsiglen\fR is a
valid \s-1ECDSA\s0 signature of the hash value \fBdgst\fR of size \fBdgstlen\fR using the
public key \fBeckey\fR.  The parameter \fBtype\fR is ignored.
.PP
\&\fBECDSA_do_verify()\fR is similar to \fBECDSA_verify()\fR except the signature is
presented in the form of a pointer to an \fB\s-1ECDSA_SIG\s0\fR structure.
.PP
The remaining functions utilise the internal \fBkinv\fR and \fBr\fR values used
during signature computation. Most applications will never need to call these
and some external \s-1ECDSA ENGINE\s0 implementations may not support them at all if
either \fBkinv\fR or \fBr\fR is not \fB\s-1NULL\s0\fR.
.PP
\&\fBECDSA_sign_setup()\fR may be used to precompute parts of the signing operation.
\&\fBeckey\fR is the private \s-1EC\s0 key and \fBctx\fR is a pointer to \fB\s-1BN_CTX\s0\fR structure
(or \s-1NULL\s0). The precomputed values or returned in \fBkinv\fR and \fBrp\fR and can be
used in a later call to \fBECDSA_sign_ex()\fR or \fBECDSA_do_sign_ex()\fR.
.PP
\&\fBECDSA_sign_ex()\fR computes a digital signature of the \fBdgstlen\fR bytes hash value
\&\fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR and the optional pre-computed values
\&\fBkinv\fR and \fBrp\fR. The \s-1DER\s0 encoded signature is stored in \fBsig\fR and its
length is returned in \fBsig_len\fR. Note: \fBsig\fR must point to ECDSA_size(eckey)
bytes of memory. The parameter \fBtype\fR is ignored.
.PP
\&\fBECDSA_do_sign_ex()\fR is similar to \fBECDSA_sign_ex()\fR except the signature is
returned as a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error).
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBECDSA_SIG_new()\fR returns \s-1NULL\s0 if the allocation fails.
.PP
\&\fBECDSA_SIG_set0()\fR returns 1 on success or 0 on failure.
.PP
\&\fBECDSA_SIG_get0_r()\fR and \fBECDSA_SIG_get0_s()\fR return the corresponding value,
or \s-1NULL\s0 if it is unset.
.PP
\&\fBECDSA_size()\fR returns the maximum length signature or 0 on error.
.PP
\&\fBECDSA_sign()\fR, \fBECDSA_sign_ex()\fR and \fBECDSA_sign_setup()\fR return 1 if successful
or 0 on error.
.PP
\&\fBECDSA_do_sign()\fR and \fBECDSA_do_sign_ex()\fR return a pointer to an allocated
\&\fB\s-1ECDSA_SIG\s0\fR structure or \s-1NULL\s0 on error.
.PP
\&\fBECDSA_verify()\fR and \fBECDSA_do_verify()\fR return 1 for a valid
signature, 0 for an invalid signature and \-1 on error.
The error codes can be obtained by \fBERR_get_error\fR\|(3).
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Creating an \s-1ECDSA\s0 signature of a given \s-1SHA\-256\s0 hash value using the
named curve prime256v1 (aka P\-256).
.PP
First step: create an \s-1EC_KEY\s0 object (note: this part is \fBnot\fR \s-1ECDSA\s0
specific)
.PP
.Vb 3
\& int ret;
\& ECDSA_SIG *sig;
\& EC_KEY *eckey;
\&
\& eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
\& if (eckey == NULL)
\&     /* error */
\& if (EC_KEY_generate_key(eckey) == 0)
\&     /* error */
.Ve
.PP
Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA\-256\s0 hash value
using \fBECDSA_do_sign()\fR:
.PP
.Vb 3
\& sig = ECDSA_do_sign(digest, 32, eckey);
\& if (sig == NULL)
\&     /* error */
.Ve
.PP
or using \fBECDSA_sign()\fR:
.PP
.Vb 2
\& unsigned char *buffer, *pp;
\& int buf_len;
\&
\& buf_len = ECDSA_size(eckey);
\& buffer = OPENSSL_malloc(buf_len);
\& pp = buffer;
\& if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0)
\&     /* error */
.Ve
.PP
Third step: verify the created \s-1ECDSA\s0 signature using \fBECDSA_do_verify()\fR:
.PP
.Vb 1
\& ret = ECDSA_do_verify(digest, 32, sig, eckey);
.Ve
.PP
or using \fBECDSA_verify()\fR:
.PP
.Vb 1
\& ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey);
.Ve
.PP
and finally evaluate the return value:
.PP
.Vb 6
\& if (ret == 1)
\&     /* signature ok */
\& else if (ret == 0)
\&     /* incorrect signature */
\& else
\&     /* error */
.Ve
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1ANSI X9.62, US\s0 Federal Information Processing Standard \s-1FIPS 186\-2\s0
(Digital Signature Standard, \s-1DSS\s0)
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEC_KEY_new\fR\|(3),
\&\fBEVP_DigestSignInit\fR\|(3),
\&\fBEVP_DigestVerifyInit\fR\|(3),
\&\fBi2d_ECDSA_SIG\fR\|(3),
\&\fBd2i_ECDSA_SIG\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2004\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.

MR SKB