Standard preamble:
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.... 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 -- \(*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\} . 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.
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'.
.. .nr rF 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 . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . 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 . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . 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 .\} ========================================================================
Title "EVP_DIGESTSIGNINIT 3"
way too many mistakes in technical documents.
\fBEVP_DigestSignInit() sets up signing context ctx to use digest type from \s-1ENGINE\s0 e and private key pkey. ctx must be created with \fBEVP_MD_CTX_new() before calling this function. If pctx is not \s-1NULL,\s0 the \s-1EVP_PKEY_CTX\s0 of the signing operation will be written to *pctx: this can be used to set alternative signing options. Note that any existing value in \fB*pctx is overwritten. The \s-1EVP_PKEY_CTX\s0 value returned must not be freed directly by the application if ctx is not assigned an \s-1EVP_PKEY_CTX\s0 value before being passed to EVP_DigestSignInit() (which means the \s-1EVP_PKEY_CTX\s0 is created inside EVP_DigestSignInit() and it will be freed automatically when the \s-1EVP_MD_CTX\s0 is freed).
The digest type may be \s-1NULL\s0 if the signing algorithm supports it.
No \s-1EVP_PKEY_CTX\s0 will be created by EVP_DigestSignInit() if the passed ctx has already been assigned one via EVP_MD_CTX_set_pkey_ctx\|(3). See also \s-1SM2\s0\|(7).
Only \s-1EVP_PKEY\s0 types that support signing can be used with these functions. This includes \s-1MAC\s0 algorithms where the \s-1MAC\s0 generation is considered as a form of \*(L"signing\*(R". Built-in \s-1EVP_PKEY\s0 types supported by these functions are \s-1CMAC,\s0 Poly1305, \s-1DSA, ECDSA, HMAC, RSA,\s0 SipHash, Ed25519 and Ed448.
Not all digests can be used for all key types. The following combinations apply.
If RSA-PSS is used and restrictions apply then the digest must match.
\fBEVP_DigestSignUpdate() hashes cnt bytes of data at d into the signature context ctx. This function can be called several times on the same ctx to include additional data. This function is currently implemented using a macro.
\fBEVP_DigestSignFinal() signs the data in ctx and places the signature in sig. If sig is \s-1NULL\s0 then the maximum size of the output buffer is written to the siglen parameter. If sig is not \s-1NULL\s0 then before the call the \fBsiglen parameter should contain the length of the sig buffer. If the call is successful the signature is written to sig and the amount of data written to siglen.
\fBEVP_DigestSign() signs tbslen bytes of data at tbs and places the signature in sig and its length in siglen in a similar way to \fBEVP_DigestSignFinal().
The error codes can be obtained from ERR_get_error\|(3).
\fBEVP_DigestSign() is a one shot operation which signs a single block of data in one function. For algorithms that support streaming it is equivalent to calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which do not support streaming (e.g. PureEdDSA) it is the only way to sign data.
In previous versions of OpenSSL there was a link between message digest types and public key algorithms. This meant that \*(L"clone\*(R" digests such as EVP_dss1() needed to be used to sign using \s-1SHA1\s0 and \s-1DSA.\s0 This is no longer necessary and the use of clone digest is now discouraged.
For some key types and parameters the random number generator must be seeded. If the automatic seeding or reseeding of the OpenSSL \s-1CSPRNG\s0 fails due to external circumstances (see \s-1RAND\s0\|(7)), the operation will fail.
The call to EVP_DigestSignFinal() internally finalizes a copy of the digest context. This means that calls to EVP_DigestSignUpdate() and \fBEVP_DigestSignFinal() can be called later to digest and sign additional data.
Since only a copy of the digest context is ever finalized, the context must be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak will occur.
The use of EVP_PKEY_size() with these functions is discouraged because some signature operations may have a signature length which depends on the parameters set. As a result EVP_PKEY_size() would have to return a value which indicates the maximum possible signature for any set of parameters.
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>.