STEGANOGRAPHY

Steganography, coming from the Greek words stegos, meaning roof or covered and graphia which means writing, is the art and science of hiding the fact that communication is taking place. Using steganography, you can embed a secret message inside a piece of unsuspicious information and send it without anyone knowing of the existence of the secret message. Steganography and cryptography are closely related. 

Cryptography scrambles messages so they cannot be understood. Steganography on the other hand, will hide the message so there is no knowledge of the existence of the message in the first place. In some situations, sending an encrypted message will arouse suspicion while an ”invisible” message will not do so. Both sciences can be combined to produce better protection of the message. In this case, when the steganography fails and the message can be detected, it is still of no use as it is encrypted using cryptography techniques. 

New technology

Steganographic techniques have been used for centuries. A different method from that time used wax tables as a cover source. Text was written on the underlying wood and the message was covered with a new wax layer. The tablets appeared to be blank so they passed inspection without question.

Uses of steganography

With steganography you can send messages without anyone having knowledge of the existence of the communication. There are many countries where it is not possible to speak as freely as it is in some more democratic countries. Steganography can be a solution which makes it possible to send news and information without being censored and without the fear of the messages being intercepted and traced back to you. While sending messages can be useful, it is also possible to simply use steganography to store information on a location. For example, several information sources like your private banking information, some military secrets and your mothers special pancake recipe, can be stored in a cover source. When you are required to unhide the secret information in your cover source, you can easily reveal your banking data and the recipe and it will be impossible to prove the existence of the military secrets inside. Steganography can offer deniable storage of information.

The offers an implementation of this principle. Because you can hide information without the cover source changing, steganography can also be used to implement watermarking. Although the concept of watermarking is not necessarily steganography, there are several steganographic techniques that are being used to store watermarks in data. The main difference is on intent, while the purpose of steganography is hiding information, watermarking is merely extending the cover source with extra information. Since people will not accept noticeable changes in images, audio or video files because of a watermark, steganographic methods can be used to hide this.

Implementing steganography

Secrets can be hidden inside all sorts of cover information: text, images, audio, video and more. Most steganographic utilities nowadays, hide information inside images, as this is relatively easy to implement. However, there are tools available to store secrets inside almost any type of cover source. It is also possible to hide information inside texts, sounds and video films for example. The most important property of a cover source is the amount of data that can be stored inside it, without changing the noticeable properties of the cover. When an image is distorted or a piece of music sounds different than the original, the cover source will be suspicious and may be checked more thoroughly.