How to protect my privacy ? Cryptography vs. Steganography.

Luxembourg on October 5, 2016 | MIA-COM
keywords : cryptography, steganography, privacy, security.

When we think about how to protect our privacy, we think about the way to keep our informations private. It doesn’t mean we are doing in life some reprehensible, illegal or even bad things, it just means that we want nobody to access our informations.
Historically people looked for keeping their informations secret, and communicating them hidden from the world. It is true when it comes to military and defense matters, and nowadays when it comes to economic matters too.
In order to keep informations private there are two solutions : cryptography and steganography. In both cases the sender and the recipient of the coded message have to know the code key, but that is the only common point between those two techniques.


To make it simple we will remind here the “Caesar Cipher” case.
In order to communicate freely and securely with his generals, the roman emperor invented a way to encrypt messages that is called “Caesar Cipher”. The process looks simple. For each letter from the message to encrypt you use a right shift of 3 (the code key is ‘+3’). Therefore A becomes D, B becomes E, and so on, and we start again at the end of the alphabet, X becomes A, Y becomes B, Z becomes C.

In order to decrypt this message, you just have to convert each letter of the encrypted message into non encrypted letters using a left shift of 3.
You can imagine all the possible variants in making the key right shift or left shift. Make your children play to code/decode messages when in long car trips, you will see them very interested, kids like secrets.
When you intercept an encrypted message, you immediately understand that it is encrypted. It immediately draws attention. That is not the case with steganography.


Let’s start with an example. You find on the living-room table the following message :

- vinegar : 2
- turnip : 1
- carrot : 1
- water : 5

It comes immediately to your mind that it is a grocery list (that has nothing to do on the living-room table by the way). You don’t pay too much attention to it, even maybe put it straight to garbage can. You even can open the window and tell every passerby what is on it and you’ll get nothing better than : “Yes, so what ?”.
Yes but if you have the following key that only the sender and the recipient know (as in the cryptography case) then everything becomes clear :

- line 1 : hour (first digit)
- line 2 : hour (second digit)
- line 3 : minute (first digit)
- line 4 : minute (second digit)

The message you guessed a grocery list without any importance becomes the time of an appointment (21.15 to be specific) the sender let on the table in order to communicate to the recipient, who will get the message later, without any physical contact between the sender and the recipient or even any recipient identity indication. Here too, when your children are tired of cryptography, make them discover steganography, they will like it.


Cryptography is a good way to assure information confidentiality but immediately dawn attention from the interceptor and will be tempted to decode. On the other hand steganography hide the coded message inside a harmless message, that doesn’t dawn attention and then doesn’t need to be hidden.
Every message can then be an example of cryptography or steganography, maybe even this article, who knows ?