'\" t
.\"     Title: kcapi_akcipher_sign
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: April 2024
.\"    Manual: Programming Interface
.\"    Source: libkcapi Manual 1.4.0
.\"  Language: English
.\"
.TH "KCAPI_AKCIPHER_SIGN" "3" "April 2024" "libkcapi Manual 1\&.4\&.0" "Programming Interface"
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.SH "NAME"
kcapi_akcipher_sign \- signature generation
.SH "SYNOPSIS"
.HP \w'ssize_t\ kcapi_akcipher_sign('u
.BI "ssize_t kcapi_akcipher_sign(struct\ kcapi_handle\ *\ " "handle" ", const\ uint8_t\ *\ " "in" ", size_t\ " "inlen" ", uint8_t\ *\ " "out" ", size_t\ " "outlen" ", int\ " "access" ");"
.SH "ARGUMENTS"
.PP
\fIhandle\fR
.RS 4
[in] cipher handle
.RE
.PP
\fIin\fR
.RS 4
[in] message data buffer
.RE
.PP
\fIinlen\fR
.RS 4
[in] length of in buffer
.RE
.PP
\fIout\fR
.RS 4
[out] signature data buffer
.RE
.PP
\fIoutlen\fR
.RS 4
[in] length of out buffer
.RE
.PP
\fIaccess\fR
.RS 4
[in] kernel access type (KCAPI_ACCESS_HEURISTIC \- use internal heuristic for fastest kernel access; KCAPI_ACCESS_VMSPLICE \- use vmsplice access; KCAPI_ACCESS_SENDMSG \- sendmsg access)
.RE
.SH "DESCRIPTION"
.PP
It is perfectly legal to use the same buffer as the message and signature pointers\&. That would mean that after the signature generation operation, the message is overwritten with the signature\&.
.PP
The memory should be aligned at the page boundary using posix_memalign(sysconf(_SC_PAGESIZE)), If it is not aligned at the page boundary, the vmsplice call may not send all data to the kernel\&.
.PP
If the output size is insufficiently large, \-EINVAL is returned\&. The output buffer must be at least as large as the modululs of the uses key\&.
.PP
\fIreturn\fR
number of bytes returned by the signature gen operation upon success; a negative errno\-style error code if an error occurred
.SH "AUTHOR"
.PP
\fBStephan Mueller\fR <\&smueller@chronox.de\&>
.RS 4
Author.
.RE
.SH "COPYRIGHT"
.br