So to help identify what is meant by watermarking please read the following sections that describe the commonest meanings in more detail, and then go on to describe which watermark methods are supported by Locklizard and how they may be implemented.
Most people are familiar with two types of document watermarks which can be found in banknotes or on checks.
But in text files there is nowhere to ‘hide’ the watermark.
Also, whilst these watermarks act to identify the owner of the original they don’ t tell you anything about who was actually authorized to use them. Several patents appear to have been granted over the use of digital watermarks as a method of demonstrating that a document that is encoded as a picture is genuine (but not necessarily original).
However, it is not a very useful method if you are trying to protect information such as text or similar.
This is because to hide these kinds of watermarks in a file you need to be able to alter lots of bits without anyone being able to notice.
The notion of watermarks as a means of identification was carried beyond the printing press into the computer age.
Information directly encoded into the data portion of an image, video, or audio file that identifies the copyright owner or a licensed user.
The intention is either that in the event the images are copied then the ownership is not in dispute, or to prevent any realistic commercial use of the images if they are copied because their quality would not be acceptable. These digital watermarks are created by embedding extra information, commonly in the form of digital patterns, into the computer files containing the images or sounds to be protected. The second is to make it much more difficult for someone to remove the pattern because they do not know what they are looking for.
For this to be successful, the addition of the image to the information in the file must have no noticeable effect as far as the person seeing the subsequent picture or hearing the sound. In this case, the owner is using the watermark to help identify the source of the copy, since they cannot prevent the copying.