Pertemuan 3 information hiding steganography https://spada.teknokrat.ac.id

1. NETWORK SECURITY
Jupriyadi, S.Kom. M.T.
jupriyadi@teknokrat.ac.id
Bandarlampung, Maret 2020
https://spada.teknokrat.ac.id
Chapter 3

2. • To be understand the basic concepts of steganography
• The student will be able hide the message using
steganography techniques

4. Steganography is the art and science of writing hidden
messages in such a way that no-one apart from the sender and
intended recipient even realizes there is a hidden message, a
form of security through obscurity

5. Cryptography is the study of secure communications
techniques that allow only the sender and intended recipient of
a message to view its contents. The term is derived from the
Greek word kryptos, which means hidden. It is closely
associated to encryption, which is the act of scrambling
ordinary text into what's known as ciphertext and then back
again upon arrival

6.  Greek Words : STEGANOS – “Covered” GRAPHIE – “Writing”
 Steganography is the art and science of writing hidden
messages in such a way that no one apart from the intended
recipient knows of the existence of the message.
 This can be achieve by concealing the existence of information
within seemingly harmless carriers or cover
 Carrier: text, image, video, audio, etc.

7. The primary goal of steganography is to hide a message inside
another message in a way that avoids drawing suspicion to the
transmission of the hidden message.
If suspicion is raised, then the goal is defeated.

8. Early steganography
Pictographs: e.g., Sherlock Holmes’s
Dancing Men.
Thousands of years ago, the
Greeks used steganography to
hide information from their
enemies.
One hiding method was to engrave a message
in a block of wood, then cover it with wax, so it
looked like a blank wax tablet. When they
wanted to retrieve the message, they would
simply melt off the wax.

9. Invisible Ink
 Write with lemon juice and a
toothpick / cotton swab. Let the paper
dry.
 Heat the paper with an iron to reveal
the hidden message.

10. Null Cipher
Fishing freshwater bends and saltwater coasts rewards
anyone feeling stressed. Resourceful anglers usually find
masterful leapers fun and admit swordfish rank
overwhelming anyday.
“Send lawyers, guns, and money”

11. LSB (least significant bit)

12. LSB Steganography ... ?
LSB-Steganography is a steganography technique in which
we hide messages inside an image by replacing Least
significant bit of image with the bits of message to be hidden

13. LSB Technique
Suppose we want to encode the letter A (ASCII 65 or binary
01000001) in the following 8 bytes of a carrier file.
01011101 11010000 00011100 10101100
11100111 10000111 01101011 11100011
becomes
01011100 11010001 00011100 10101100
11100110 10000110 01101010 11100011

14. LSB Technique
Everything in a computer is stored as 1’s and 0’s (a bit).
Bits are grouped in sets of eight, one set is called a byte.
One byte can be used to represent each letter of the
alphabet. This is what is used in text files.

15. LSB Technique
Pictures are made up of lots of little dots called pixels. Each pixel is
represented as 3 bytes – one for red, one for green and one for blue.
Each byte is interpreted as a number, which is how much of
that colour is used to make the final colour of the pixel.

16. LSB Technique
The difference between two colours that differ by one in either one red,
green or blue value is impossible to see with the human eye.
• If we change the least significant (last) bit in a byte, we either add or
subtract one from the value it represents.
• This means we can overwrite the last bit in a byte without affecting the
colour it appears to be.

17. LSB Technique
We can use images to hide things if we replace the last bit of
every colour’s byte with a bit from the message.

18. LSB Technique
Even if we do this across a big image and with a really large
message, it is still hard to tell that anything is wrong.

19. LSB Technique
Normally when we hide a message in an image we just start at the top left
pixel and keep writing across the image until we are done.
This may appear to work quite well,
but if we zoom right in and look at
the pixels in a block of plain colour
then we can see that some pixels
aren’t all the same.

20. LSB Technique
If we change an edge it is harder to notice because two pixels
next to each other will already have very different colours.
So what we want to do is hide in the edges of a picture because
then we can avoid hiding in blocks of colour.

21.  Network Security Essentials Fourth Edition – William
Stallings – 2011
 Fundamental of Network Security – John E. Canavan -
2001
 A.Kizza, Joseph M. 2015. Guide to Computer Network
Security. London: Springer
 Perez, A. 2014. Network Security. New Jersey: Wiley
 Keamanan Sistem Informasi Berbasis Internet – Budi
Raharjo – 2002

22. What's Next ?

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