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                           !Conceal !Help file 
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Version: 1.0 (31 July 2000)

Author: Nat Queen <n.m.queen@birmingham.ac.uk>

Primary distribution site: http://web.bham.ac.uk/N.M.Queen/pgp/acorn.html


What does it do?
================

!Conceal is a program for hiding files. Unlike some of the other security
applications available from the same URL, it does not encrypt the files. It
attaches a file to be hidden to the end of some other file, such as an
image, sound or video file, which is not normally examined with an editor.
Thus, the hidden file does not show up in any directory. If a smaller file
is hidden by attaching it to a much larger file, it is unlikely that casual
checks of the file length or of the directory structure would suggest
anything ususual. In most cases, the modified image, sound or video file
functions normally when viewed or played by means of standard applications.

!Conceal is intended to provide only casual security. If the modified files
are examined with an editor such as !Edit or !Zap, the 'hidden' file becomes
immediately obvious. Moreover, anyone with a copy of !Conceal can easily
extract the hidden file. If you want high security, you should use one of
the file-encryption programs available from the URL given above. You can
combine encryption with concealment. If you hide a strongly encrypted file
by means of !Conceal, you can at least be sure that any snooper who manages
to find the hidden file will still be unable to discover its contents.

The following terminology will be used in what follows. Any file to be
hidden by !Conceal will be referred to as a data file. This does *not* mean
that it has the filetype 'data'. The filetype can be arbitrary, and *any*
file can be a data file. A file to which a data file is attached will be
called a container file. A container file can also be arbitrary, but for
obvious reasons the only useful container files are files which are not
normally examined with an editor. A container file to which a data file is
actually attached will be called an extended container file.

Most extended image files (sprites, GIFs, JPEGs, etc.) can be viewed
normally by means of various applications. However, some extended sprites
cannot be viewed with !Paint, which reports that they are corrupted (though
many other popular applications for processing images seem to display them
normally). Most extended sound or video files also seem to function
normally in applications for playing them.

If you choose to use sprites as container files, the concealment may be
particularly effective if you use the sprites which are already present
inside standard applications. Whatever you choose, in order to avoid
arousing suspicion if any snoopers examine your files, it is advisable to
check that the extended container files still work normally in the
appropriate applications installed in your computer.

!Conceal has certain advantages over the steganographic program !Stego,
available from the same URL. Unlike !Stego, !Conceal can hide any file (not
necessarily a text file) in any type of container file (not necessarily a
sprite). On the other hand, !Stego offers greater security, since it hides a
file by encoding it within the body of a sprite file in such a way that the
hidden file cannot be detected by simple examination of the sprite file.

It should be pointed out that !Conceal is not suitable for preparing
material to be sent over the Internet, since the 'hidden' file attached to a
container file is not encrypted and would be completely readable if the
transmission is intercepted.


How to use !Conceal
===================

When you run !Conceal, a directory window will open, showing two inner
applications, !Hide-it and !Reveal-it. These are used for hiding a data file
in a container file or for recovering the data file from an extended
container file.


!Hide-it
========

Run !Hide-it, and two new directory windows will open, showing the
directories 'DataDir' and 'ConDir'. Nothing else will happen if one or both
of those directories are empty.

To hide a data file, put it in the directory 'DataDir', and put your chosen
container file in the directory 'ConDir'. Then run !Hide again. A copy of
the data file will be added to the end of the container file, and the
original copy of the data file in the directory 'DataDir' will be deleted.
You can then move the extended container file to any directory of your
choice.


!Reveal-it
==========

To recover a hidden data file from an extended container file, run
!Reveal-it. A directory window for the directory 'ConDir' will open, but
nothing else will happen if that directory is empty.

Put the extended container file in that directory and run !Reveal-it again.
A directory window for the directory DataDir will open, and it will contain
a copy of the data file which was extracted from the extended container
file. The extended container file will be deleted.

The extracted data file is always given the filename 'data' and the filetype
'text'. You can rename the file and redefine its filetype if necessary.

If you attempt to extract a data file from any file which has not actually
been processed by !Hide-it, i.e. which is not actually an extended container
file, !Reveal-it will report this and will perform no further action.


Legal notice
============

!Conceal is freeware. The copyright is retained by the author, Nat Queen. 
You may copy and distribute this software freely as long as none of the
files are altered or removed. If you distribute !Conceal in any PD library,
magazine cover disc or CD, or on any site on the Internet, please drop a
line about it in my mailbox, so that I can keep you informed about possible
future updates. Any distribution method is allowed, provided that you do not
make any profit from it. This software must not be distributed as part of
any other application without my prior permission.

This software has been thoroughly tested, but no guarantee is given as to
its suitability for any purpose. The author accepts no responsibility for
any data loss, crashes or other undesired effects caused directly or
indirectly by using !Conceal.
