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.