Esteganografia

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If the photograph meets the conditions of its own intellectual creation of the author, is considered a photographic work. Author of such photographic work obtains a photo copyright which consists of personality and equity components. Creation of the copyright to the photography is automatic and it is no need for the registration, but it brings disadvantages as well, because without registering it is not clearly and easily demonstrable, who has the copyright. This condition is favouring the plagiarists. Author of the photography, to prove his rights, must use all means legal and technical, to make his authorship of the picture clear and demonstrable. One of the basic things that every author should do is to realize his basic right and photography mark with his name or a pseudonym. Marking the photo can be done by inserting the author‟s name directly on the photo or photo below, while the menu can be supplied with the character © (copyright) and date of the work creation. Indication of authorship can also be put under the photo, or next to it. To indicate the name of the author photo in electronic form, there are several technical methods, which should act as a preventative proof of authorship [K. Babiaková, Praktické rady ako chrániť autorské práva, 2-4].

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Methods of protection

- EXIF

Keep the original photos with precise and original EXIF (Exchangeable image file format – information set, which are attached at each image that the camera will shoot). EXIF can carry information about:[pic 5]

the author,

date and time of design or date of the last modification of the picture, data on the camera and lens (brand, exact model),

exposure data (exposure time and aperture values and also other camera settings)

These are the basic information that a metadata file can contain. The advantage is that inside EXIF in some programs, you can write the name or other information about authorship. Some programs can even lock this information. The disadvantage, however, is that many programs allow you to change information in the EXIF, even those that are locked. Basically every software and digital lock is attacked by hackers [K. Babiaková, Praktické rady ako chrániť autorské práva, 4-5].

- Authorization software

Buy a more expensive software (around hundreds of euros) called Authorization software, which connects to every photo an unique code and registers photos in the database [K. Babiaková, Praktické rady ako chrániť autorské práva, 5].

- Watermark

To images that we want to potentially sell them or prove something, we can bet watermark. Watermark (semi-transparent or translucent character that allows picture to be viewed and to evaluate the content and quality, but given that overlaps the picture, does not allow its use for commercial purposes or otherwise unlawfully use). However, it can be removed by a variety of software. The more complex and clearer watermark is, the harder is to remove it [K. Babiaková, Praktické rady ako chrániť autorské práva, 5].

2.2. Protection on Internet

All of these methods have a number of disadvantages. They are generally known or readily removable protecting authorship marks, or are relatively expensive. Photographers who shoot on film have a simpler demonstration of authorship in that they have more negatives, which should demonstrate that the person who owns them is also the author of the photographs. In the case of digital photography, proving is complex, even more if the photo is stored on a publicly accessible digital repository or the Internet.

Computers connected into network are strong and may serve to share your experiences represented by photography with your friend, family or just with public. But in the other hand, it may be risky when you allow access to your photo gallery for public. Some authors [2] are saying: “…PC could become an instrument of manipulation, corruption and dehumanization, of alienation for the ontological man, the spiritual being, face of God saved by the universal sacrifice of the Cross of Christ”. If the photos are placed online, author cannot be sure by any system of the protection of his rights. Scripts „right-click‟ can circumvent direct source view, drop down images can be circumvented in the same way, the watermark can be removed (sometimes with difficulty). Even if the photo is inserted into the Flash object, one can easily create a screenshot [L. Kyrnin, How to Protect Your Digital Photos from Being Copied, accessed 20.03.2014, http://webdesign.about.com/od/graphics/a/aa102406.htm]. In this case the author must find an alternative method of protection. A suitable alternative is to locate information directly to the user‟s profile photo (not the notorious metadata).

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Steganography methods

The following formula provides a very generic description of the pieces of the steganographic process:

cover_medium + hidden_data + stego_key = stego_medium (1) In this context, the cover_medium is the file in which we will hide the hidden_data, which may also be encrypted using the stego_key. The resultant file is the stego_medium (which will, of course be the same type of file as the cover_medium). The cover_medium (and, thus, the stego_medium) are typically

image or audio files. In this article, I will focus on image files and will, therefore, refer to the cover_image and stego_image.

Before discussing how information is hidden in an image file, it worth a fast review of how images are stored in the first place. An image file is merely a binary file containing a binary representation of the colour or light intensity of each picture element (pixel) comprising the image.

Images typically use either 8-bit or 24-bit colour. When using 8-bit colour, there is a definition of up to 256 colours forming a palette for this image, each colour denoted by an 8-bit value. A 24-bit colour scheme, as the term suggests, uses 24 bits per pixel and provides a much better set of colours. In this case, each pixel is represented by three bytes, each byte representing the intensity of the three primary colours red, green, and blue respectively (RGB). The Hypertext Markup Language (HTML) format for indicating colours in a Web page often uses a 24-bit format employing six hexadecimal