Type spacing or type offsetting is a way of subtly distorting the text in a message to hide additional data. Type spacing was created as a way to discourage illegal copying of textual material. While this makes its intended purpose as a form of watermark, type spacing can also be used to send a message in secret. To encode a secret message using type spacing all one would have to do is adjust specific letters ever so slightly from their normal position. The letters that are out of position indicate the secret message.
This form of steganography can be used with a good deal of flexibility by either adjusting the white space between the letters or the words, or by slightly shifting entire blocks of words from their original position. This is the nondigital form of this type of steganography (Figure 2.3).
The digital approach uses the actual positions of the lines or the words in the document to indicate a 1 or 0 position. These subtle position shifts are created and detected by the stego-algorithm, which when run will indicate a 1 or 0 and, ultimately, the hidden message.