2. CONTENTS
➢ What is steganogrphy
➢ Steganography vs cryptography
➢ Evolution of Steganography
➢ Types of Steganography
➢ Image Steganography
➢ LSB Algorithm
➢ Encoding text into image
➢ Decoding text into image
➢ Advantages and Disadvantages
3. WHAT IS STEGANOGRAPHY
⮚ The word steganography literally means covered writing as derived from Greek. In
broad sense, term Steganography is used for hiding message within an image.
⮚ In contrast to cryptography, where the "enemy" is allowed to detect, intercept and
modify messages without being able to violate certain security premises
guaranteed by a cryptosystem, The goal of steganography is to hide messages
inside other "harmless" messages in a way that does not allow any "enemy" to even
detect that there is a second secret message present.
4. STEGANOGRAPHY VS
CRYPTOGRAPHY
⮚ Cryptographic techniques "scramble" messages so if intercepted, the
messages cannot be understood. Steganography, an essence, "camouflages"
a message to hide its existence and make it seem "invisible" thus
concealing the fact that a message is being sent altogether. An encrypted
message may draw suspicion while an invisible message will not.
⮚ Steganography cannot be detected. Therefore, it is used when encryption
is not permitted. Or, more commonly, steganography is used to
supplement encryption
5. EVOLUTION OF
STEGANOGRAPHY
⮚ INVISIBLE INK : An innocent letter may contain a very different message
written between the lines with invisible ink. Common sources for invisible
inks are milk, vinegar, fruit juices and urine. All of these darken when
heated. Later on, more sophisticated inks were developed which react to
various chemicals.
⮚ MICRODOTS: Microdots are photographs the size of a printed period having
the clarity of standard-sized typewritten pages.. The message was not
hidden, nor encrypted. It was just so small as to not draw attention to
itself (for a while). Besides being so small, microdots permitted the
transmission of large amounts of data including drawings and photographs
6. TYPES OF STEGANOGRAPHY
⮚ Messages in text program is called SPAM MIMIC.
⮚ Messages in still Images most popular in modern world
⮚ Messages in video embedding information into multimedia data has gained
increasing attention lately.
7. AN EXAMPLE
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”
8. IMAGE STEGNOGRAPHY
⮚ Steganography is a term used for hiding messages within an image. Any
color pixel is made of a combination of red –green-blue mode(RGB)
wherein each RGB component consist of 8 bits. If letters in ASCII are to be
represented within the color pixels, the rightmost digit, called the least
significant bit (LSB), can be altered.
⮚ Any variation in the value of this bit leads to very minimal variation in
color. If we have to hide the word ‘Hello’ in the image, we take the LSB of
every color and hide each bit of the word in its RGB combination.
⮚ To insert the letter ‘H’ we modify three color pixels with three bits in
each color pixel, we utilize 15 color pixels to hide the entire word with
only 1 bit in the 14th pixel.
9. LSB ALGORITHM
► Extract the pixel from the Image.
► Extract the characters from the text.
► Convert the letters into their ascii values.
► From the ascii values convert them into their respective binary bits.
► Place some termination to indicate the end of the message.
10. ENCODING TEXT INTO IMAGE
H E L L O
Ascii value
Binary value
H E
72 69
01001000 01000101
(8 bits) (8 bits)
11. (113,45,201) (96,121,89) (54,189,224)
PIXEL PIXEL PIXEL
1 0 0 0
0 1 0 0
⮚ If, bit = 0 -> then make the RGB value even.
⮚ If, bit = 1 -> then make the RGB value odd.
+1
+1 +1 +1
ENCODING BINARY BITS INTO PIXELS
13. DECODING THE IMAGE
⮚ Take three pixel at a time and build the binary bits from them.
⮚ From the binary value we can now convert them into their ascii values.
⮚ From the ascii values we represent the actual letters in the message.
⮚ And verify if the message ends or not from the last bit of the third pixel.
16. ADVANTAGES OF STEGANOGRAPHY
⮚ It can be used for safeguarding data, such as in the
field of media where copywriting ensures
authenticity.
⮚ It can be used by intelligence agencies for sending
their secret data.
17. DISADVANTAGES OF STEGANOGRAPHY
⮚ Many a terrorist and anti humanist activities have been carried out
cloaked under this technique.
⮚ The major disadvantage of steganography is that, unlike cryptography,
it needed a lot of overhead to hide associatively few bits of
information. Because the steganographic system is found, it is
rendered useless. However, it fares no worse than cryptography and is
still the preferred medium.
18. CONCLUSION
Steganography transmits secrets through apparently innocuous covers in an
effort to conceal the existence of a secret. Digital image steganography and its
derivatives are growing in use and application. In areas where cryptography and
strong encryption are being outlawed, citizens are looking at steganography to
circumvent such policies and pass messages covertly. As with the other great
innovations of the digital age: the battle between cryptographers and
cryptanalysis, security experts and hackers, record companies and pirates,
steganography and Steganalysis will continually develop new techniques to
counter each other.
