Introduction
************

This is the README for `imagesign', a package to allow the digital signing
of images without changing the image format or attaching extra files.

If you or your organisation regularly produce images and you need to be able
to tell later on whether an image has been modified from the original, or
you need to be able to pass the images on to other people and they need to
be able to check whether it really is you who sent them the image, then this
utility may be useful to you.

It works by digitally signing the image itself (not including any comment
blocks) using `gpg', and then embeds that signature in the image within a
comment block.  This comment block does not affect the image in any way.

Once the image has had a signature embedded in it, you can send it, store
it, or whatever, treating it as you normally would.  However, as soon as the
image is modified in any way (even if it is just loaded and saved again),
the signature will no longer be valid and `imagesign --verify' will tell you
that the image is not the original that you signed.

Note that `imagesign' currently only works on JPEG images.  If you can add
support for other image types, please contact the author.

Read the `gpg' documentation for information on how to set up your private
key, import public keys of other people, and so on.


Requirements
************

These scripts require the following programs to be installed:

  mktemp
  gpg                 (GNU Privacy Guard, http://www.gnupg.org/)
  file
  rdjpgcom, wrjpgcom  (IJG libjpeg)

On a Red Hat system, these are available in the packages `mktemp',
`libjpeg', and `gnupg'.


Documentation
*************

A man page is included - do `man imagesign' after installation to read it.


Installation
************

Use the usual `sh ./configure; make; make install' sequence to install.


Author
******

This package is copyright (C) 2002 Andrew Wood, and is being distributed
under the terms of the Artistic License.  For more details, see the file
`doc/COPYING'.

You can contact me by email at andrew.wood@ivarch.com or by using the
contact form on my web page at http://www.ivarch.com/.

The `newpackage' home page is at:

  http://www.ivarch.com/programs/imagesign.shtml

The latest version can always be found here.

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$Id: README,v 1.1.1.1 2002/11/09 14:31:13 ivarch Exp $
