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.TH SETKEY "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.

.SH NAME
setkey
\(em set encoding key
(\fBCRYPT\fP)
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>
.P
void setkey(const char *\fIkey\fP);
.fi
.SH DESCRIPTION
The
\fIsetkey\fR()
function provides access to an implementation-defined encoding
algorithm. The argument of
\fIsetkey\fR()
is an array of length 64 bytes containing only the bytes with numerical
value of 0 and 1. If this string is divided into groups of 8, the
low-order bit in each group is ignored; this gives a 56-bit key which
is used by the algorithm. This is the key that shall be used with the
algorithm to encode a string
.IR block
passed to
\fIencrypt\fR().
.P
The
\fIsetkey\fR()
function shall not change the setting of
.IR errno
if successful. An application wishing to check for error situations
should set
.IR errno
to 0 before calling
\fIsetkey\fR().
If
.IR errno
is non-zero on return, an error has occurred.
.P
The
\fIsetkey\fR()
function need not be thread-safe.
.SH "RETURN VALUE"
No values are returned.
.SH ERRORS
The
\fIsetkey\fR()
function shall fail if:
.TP
.BR ENOSYS
The functionality is not supported on this implementation.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Decoding need not be implemented in all environments. This is related
to government restrictions in some countries on encryption and
decryption routines. Historical practice has been to ship a different
version of the encryption library without the decryption feature in the
routines supplied. Thus the exported version of
\fIencrypt\fR()
does encoding but not decoding.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIcrypt\fR\^(\|)",
.IR "\fIencrypt\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "\fB<stdlib.h>\fP"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .

Any typographical or formatting errors that appear
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