ZIPD is a small utility which encrypts a .ZIP file so that it cannot be
recognized by any other software as a .ZIP file.

The reason for doing this is that many email servers these days do not
allow .ZIP files to be attached, or scan through them looking for .EXEs
and other things deemed to be "unsafe". While this supposedly "protects"
those people who don't know better than to execute anything which shows
up in their email (or are running mailers which do it for them), it is
very problematic for those of us who do real work and wish to exchange
project archives, executable utilities and other such things with our
professional collegues.

ZIPD reads a .ZIP file and creates a new file with the extension .PIZ which
contains an encrypted version of the original .ZIP file. It also adds a CRC
check of the content so that it can be validated when it is decrypted. ZIPD
uses a "seeded" encryption which means that if you encrypt the same .ZIP
file multiple times, each .PIZ created will be different (making it harder
to recognize a encrypted file).

Example:

  ZIPD /C myfile         <= Reads myfile.ZIP and creates myfile.PIZ

Now you can email myfile.PIZ along with instruction on where to obtain
ZIPD to your receipient, who then performs:

  ZIPD myfile            <= Reads myfile.PIZ and recreates myfile.ZIP

Now they have the original myfile.ZIP file.

ZIPD also has the capability to mark a file with an encrypted ID which will
assure the recipient of the identity of the creator of the .PIZ file. When
the ZIP is encrypted with an identity, the identity is cryptographically
validated, and the message displayed on successful decryption and validation
is:
         ZIP decoded and validated: 'Your Identity Here'

To prevent "just anyone" from creating .PIZ files with any ID, I do not
provide this functionality in the public version of ZIPD ... If you would
like a version of ZIPD which injects your unique identity into the .PIZ
file, please contact me.

Dunfield Development Services (DDS) offers software and firmware
development services specializing in systems and embedded applications.
For more information, visit: http://www.dunfield.com

    ---- Sample "canned" response to send with rejected emails ----

Hi, I tried to send you the attachment you requested, however your email
service rejected it (quoted below):

I have therefore encrypted the .ZIP using ZIPD which is available from:

   www.classiccmp.org/dunfield

go to the "DOS Widgets" section near the end of the main page, then download
"ZIPD - ZIP encryption package".

