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SETKEY(3P)                 POSIX Programmer's Manual                SETKEY(3P)
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.
NAME
       setkey -- set encoding key (CRYPT)
SYNOPSIS
       #include <stdlib.h>
       void setkey(const char *key);
DESCRIPTION
       The setkey() function  provides  access  to  an  implementation-defined
       encoding  algorithm.  The argument of setkey() 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  algo-
       rithm.  This is the key that shall be used with the algorithm to encode
       a string block passed to encrypt().
       The setkey() function shall not change the setting of errno if success-
       ful.  An  application  wishing to check for error situations should set
       errno to 0 before calling setkey().  If errno is non-zero on return, an
       error has occurred.
       The setkey() function need not be thread-safe.
RETURN VALUE
       No values are returned.
ERRORS
       The setkey() function shall fail if:
       ENOSYS The functionality is not supported on this implementation.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       Decoding  need  not be implemented in all environments. This is related
       to government restrictions in some countries on encryption and  decryp-
       tion routines. Historical practice has been to ship a different version
       of the encryption library without the decryption feature  in  the  rou-
       tines  supplied.  Thus  the exported version of encrypt() does encoding
       but not decoding.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       crypt(), encrypt()
       The Base Definitions volume of POSIX.1-2008, <stdlib.h>
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 Electri-
       cal 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 in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           SETKEY(3P)