What is Steganography?

The term steganography is derived from the Greek words steganos (covered) and graphein (to write). Back in the day it was used a synonym for cryptography, but in 1967 the historian David Kahn redefined it as a procedure for concealing the existence of a secret message that does not necessarily have to be encrypted. The encryption of data is increasingly coming under attack due to misuse (for child pornography, terrorism or general crime). However, that should not be a reason to forego encryption, but rather a reason to hide encrypted data.

The easiest way to explain what exactly steganography is, is to say what it is not, namely cryptography. With cryptography, messages are encrypted, so outsiders see a message but not its content. In many situations, however, the actual dispatch allows unwanted conclusions to be drawn; For example, if students slip each messages on a piece of paper, it is enough for the teacher to notice and punish them, regardless of the content of the messages and whether they can be deciphered.

Of course, as with cryptography, the recipient also needs a key to read the message. A very simple example would be a text with the first letters of each line representing a message. Those who do not know this system only see the obvious, harmless text without even suspecting that there is a hidden message in it.

Steganography can easily be used on the PC for undetected communication via channels such as e-mail, WWW or social networks. The most popular options here are hiding messages in images or audio files as well as distribution via websites or blogs. For distribution via websites, you could leave fragments of your message. For the sake of simplicity, let us assume a single word as a comment on an unknown blog. Only those who know all the comments belonging to the message can put them together – and it should be clear that no one will be able to decipher this by chance.

A more common approach above all is hiding messages in files. Computed steganography all in all is a very complex topic that has a lot to do with mathematics and detailed knowledge of file structures.