For instance, steganography using sudoku puzzles has as many keys as there are possible solutions of a sudoku puzzle, which is 7021670999999999999♠ × 10 21 . 
You can also maximize your earnings by selling images together in a bundle or collection based on a theme.
Taking its name from the embossed stamp on paper, a watermark is a text or graphic image that overlaps an existing text or graphic image without obstructing it. Watermarks can be used to indicate the confidentiality of reports, whether invoices have been paid or who owns the graphic images displayed on a Web site. Following are instructions for how to make a watermark in Microsoft Word, Microsoft Excel and your graphic editor.