2. What is Steganography?
It 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.
steganography
steganós
covered
graptos
writing
The art of secret (hidden) writing
2
3. History of Steganography
An ancient Greek named Histaiaeus was
fomenting revolt against the king of Persia and
needed to pass along a message secretly.
3
4. History of Steganography
In 5th century B.C. an exiled Greek named
Demaratus wrote a warning that the Persians
planned to attack Sparta.
4
5. History of Steganography
When the USS Pueblo was captured by North Korea in
1968, the crew was forced to pose for propaganda
photos to demonstrate they were being well treated.
Their finger gestures are a form of steganography that
sends a message Americans
Fdfdsf
Fdfdsf
Dfdfd
Dsfdsf
Dsfds
5
6. Steganography Vs. Cryptography
Both have been used as means to protect
information
Cryptographic techniques "scramble" messages so
if intercepted, the messages cannot be
understood.
Steganography, in an essence, "cover-ups" a
message to hide its existence and make it seem
"invisible" thus concealing the fact that a message
is being sent altogether.
6
7. Steganography Vs. Cryptography
Original Message: Start Attacking at 11:00 Pm.
Steganography: Hiding messages within carrier objects
Cryptography: Encrypting messages
[k>>4]*2^k*257/8,s[j]=k^(k&k*2&34)
7
8. Steganography and cryptography can be
combined
The message can also be encrypted before it is
hidden inside a cover message. This provides
a double layer of protection.
Encryption will make the existence of the
message more difficult to detect, due to the
fact that some encryption techniques cause
the patterns of the characters in the
encrypted version to be more random than in
the original version.
8
9. A practical comparison of steganography and
cryptography
Purchasing some books online
Order the books online
to pay for the books by supplying our credit card
number(we check to make certain that our browser
has switched into the secure mode)
Sending our credit number should be secret and it is
our hope that the transmission is encrypted by the
browser.
Vendor can decrypt the message and read our credit
card number.
In this case, there is no need for steganography because
there is no need to hide the existence of the message.
9
10. A romantic tryst
Let’s assume that you are sending a message
to Alice (your best friend's wife) to arrange a
romantic tryst.
In this case, you would probably prefer that
neither your wife nor your best friend know
the existence of the message.
(If they learn the secret message, they may not
continue to be your wife and your best friend for
very much longer)
10
11. A romantic tryst
Use some form of steganography to hide the
existence of the secret message.
It also wouldn't hurt to encrypt the message
using Alice's public key
That way, even if the existence of the
message is detected, it wouldn't be possible
for your wife or your best friend to read it.
(That may increase your chances of survival even
if the existence of the message is detected)
11
12. How to send the message to Alice
We can use Steganography
We have different forms of Steganography to
hide the existence of the message.
The easiest way would be to send his latest
set of digital vacation photos to Alice and her
husband by embedding the message in one of
the photos.
12
13. How to send the message to Alice
Alice could extract and read your message.
Alice's husband would probably see a set of
vacation photos. The existence of a secret
message would certainly not be obvious in
viewing the photos.
Alice could embed her answer in a digital photo
of her graduation.
She could send that picture to you and your
wife.
You could extract and read the message.
Your wife could say congratulations to Alice.
13
14. How to send the message to Alice
You and Alice could continue to secretly
communicate in this manner for as long as you
could come up with reasons to exchanges
digital photos.
(That approach might get stale after a while and
you would need to come up with some other
form of steganography to continue the dialog)
14
16. Cover is the original picture, audio or video file.
Emb is the message to be embeded.
Key is the parameter which controls the hiding
process of the secret message
Stego is the resultant file that contains the hidden
message.
(We have to be careful that how much information
we try to conceal within the carrier. The longer the
message, the larger the modification of the carrier
image and the higher the probability that the
modifications can be statistically detected )
16
17. Common techniques in Steganography
Modern day steganography mainly deals with
hiding information within other files such as
Image, Audio, Video files. These files can “contain
perceptually irrelevant or redundant information
that can be substituted for hidden messages
There are three common techniques in use today:
Substitution
Injection
Generation of new files
17
18. I. Substitution
Every file that is created will contain unused or
insignificant areas of data. These areas can be
replaced without any visible changes to the
visual or audio clarity of the file.
This enables one to conceal sensitive
information within the file and still have the
file appear as though it is the same as the
original unmodified version.
18
19. I. Substitution
Also called the Least Significant Bit (LSB) method
which replaces the last bit in an 8 bit byte.
E.g. 10010110 01101010 11100101
If we change the most significant bit it would be
likely have a significant effect on the picture and
be easily seen by the naked eye. However, if we
change the last bit (1) in the last byte then
chances are that this change would not be
noticeable.
19
20. I. Substitution
LSB works best in files that have a lot of ‘noise’
i.e. Pictures that have many colors and shapes
or audio files that have a lot of different
sounds and effects such as echoes.
Substitution method generally does not
increase the size of the file but depending on
the size of the hidden message, it can
eventually cause a noticeable change from the
unmodified version.
20
21. II. Injection
Injection involves embedding the secret
message directly into the carrier object.
The problem with this approach is that it
generally makes the file larger than the
original unmodified file.
21
22. II. Generation of New Files
This technique involves taking your message and
using this to generate a new file from scratch.
22
23. Choice of Carrier
What digital format should we choose to
conceal our private message?
Steganography can be used in just about any
type of file. The most common methods used
are
a. Images
b. Audio
c. Video
23
24. Detecting the use of Steganography
Steganalysis is identifying the existence of a
hidden message in Steganography.
There are two types of attacks
Active
This involves destroying the hidden message
Passive
Detecting the use of steganography and is an
introduction to actually deciphering the hidden
message.
Viewing the file
Listening to the file
24
25. Advantages of Steganography
Securely storing sensitive data, such as
hiding system passwords or keys within other
files.
Difficult to detect.
Network surveillance and monitoring
systems will not flag messages or files that
contain Steganography data.
25
26. Disadvantages of Steganography
if someone knows the message is there, the
message can be easily read.
If you want to send large file like book, it's pretty
hard to hide with steganography
Network surveillance and monitoring systems will
not flag messages or files that contain
steganographic data. Therefore, if someone
attempted to steal confidential data, they could
conceal it within another file and send it in an
innocent looking email.
26
28. Conclusion
steganography as a tool to conceal highly
sensitive information with other digital
information. It is not a replacement for
cryptography but it is other form of hiding
information.
28
