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

       encrypt — encoding function (CRYPT)

SYNOPSIS

       #include <unistd.h>

       void encrypt(char block[64], int edflag);

DESCRIPTION

       The  encrypt()  function  shall  provide  access  to  an  implementation-defined  encoding
       algorithm. The key generated by  setkey()  is  used  to  encrypt  the  string  block  with
       encrypt().

       The  block  argument to encrypt() shall be an array of length 64 bytes containing only the
       bytes with values of 0 and 1. The array is modified in place to a similar array using  the
       key  set  by  setkey().   If  edflag  is  0,  the argument is encoded. If edflag is 1, the
       argument may be decoded (see the APPLICATION  USAGE  section);  if  the  argument  is  not
       decoded, errno shall be set to [ENOSYS].

       The encrypt() function shall not change the setting of errno if successful. An application
       wishing to check for error situations should set errno to 0 before calling encrypt().   If
       errno is non-zero on return, an error has occurred.

       The encrypt() function need not be thread-safe.

RETURN VALUE

       The encrypt() function shall not return a value.

ERRORS

       The encrypt() function shall fail if:

       ENOSYS The functionality is not supported on this implementation.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       Historical  implementations  of  the  encrypt()  function used a rather primitive encoding
       algorithm.

       In some environments,  decoding  might  not  be  implemented.  This  is  related  to  some
       Government  restrictions  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 encrypt() does encoding but not
       decoding.

RATIONALE

       None.

FUTURE DIRECTIONS

       A future version of the standard  may  mark  this  interface  as  obsolete  or  remove  it
       altogether.

SEE ALSO

       crypt(), setkey()

       The Base Definitions volume of POSIX.1‐2017, <unistd.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   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.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .