manual crypto

[lcs Mixmaster Remailer]

There's no particular need to make it a single-image random dot
stereogram.  Double images are much easier to make and provide an extra
bonus (see below).  Here is an example from a post to cypherpunks on
September 23, 1997:

VGhpcyBpcyBhIHRlc3Qg  VGhpcyBpcyBhIHRlc3Qg
bWVzc2FnZSB3aGljaCBp  bWVc2AFnZB3xaGljaCBp
cyBiZWluZyBzZW50IHZp  cyBZWmluZBzvZW50IHZp
YSBzdGVnYW5vZ3JhcGh5  YSBdGVnYW5v9Z3JhcGh5
LgpIYWQgdGhpcyBiZWVu  LgpYW1QgdhpBcyBiZWVu
IGFuIGFjdHVhbCBtZXNz  IGFIGoFjdVhXbCBtZXNz
YWdlLCBpdCB3b3VsZCBo  YWdlLCBpdCB3b3VsZCBo
YXZlIGJlZW4gZW5jcnlw  YXZIGJlZW4vgZW5jcnlw
dGVkCnVzaW5nIGEgbWV0  dGVkCVzaUW5nIGEgbWV0
aG9kIHdoaWNoIHByb2R1  aG9kIdoa4WNoIHByb2R1
Y2VzIG91dHB1dCB3aGlj  Y2VzI91dAHB1dCB3aGlj
aCBpcyBpbmRpc3Rpbmd1  aCBcyBpbmRnpc3Rpbmd1
aXNoYWJsZQpmcm9tIHJh  aXNoYWJsZQpmcm9tIHJh
bmRvbSBieXRlcy4K      bmRvbSBieXRlcy4K

Using a monospace font, let your eyes separate so the text blocks merge
and you will see the word HI displayed.

To make this all you need is a random character generator to make the
left block, and copy it to the right block.  Then take the "pixels"
where you want letters to appear and shift them one character to the
left in the right-hand block.  Use the random character generator to
fill in the blanks which this shift causes.  That's it.

The hardest part would be finding a simple block font you can use for
the letters.

Now, here's the bonus.  This is a perfect cover for sending large amounts
of random data.  Put your favorite political or sports message in the
stereogram (GO BUSH) and use the random data for steganography.

In the example above the left block is a base 64 encoding of a simple
message.  Unix users can pass the stereogram through "sed 's/ .*//'
| mimencode -u".  For a real stego message you'd use encrypted data
without any headers so it looked purely random.  There would be no way
to distinguish it from any other source of randomly generated characters.

This could even catch on as a legal "thumb your nose at the spooks"
fad, people adding random sterograms at the end of their messages.
You could even have an active .sig which had a constant message but used
different random characters each time.  There typically wouldn't be any
hidden messages, but there would be no way to be sure.