ICIECA 2014 Paper Paper 20

1. VLSI Realization of a Secure
Cryptosystem
and Steganography in Image
Encryption and Decryption
by
VANMATHI.R
&
PRABAVATHI.M 1

2. Abstract
♦ In this paper I present a technique that allows
cryptography to inherit some features from
steganography in such a way that the information
is encrypted as well as hidden. The proposed
solution is to use image cryptography to hide
textual data. The process is to transfer encrypted
textual data but in image format..
2

3. Literature Survey
Image Steganography
♦ Methods
– Replacing Least Significant Bit: The Embedding data is
hidden by replacing the least significant bit (LSB) of
each pixel in the cover image
– Replacing Moderate Significant Bit: The Embedding
data is hidden by replacing the moderate significant bit
(MSB) of each pixel in the cover image
– Transformation Domain Techniques: Other familiar
data hiding techniques use the transformation domain
of digital media to hide information. These methods
hide the messages in the significant areas of the cover
image which makes them robust against compression,
cropping and other image processing attacks
3

4. 4
Cryptography
♦ In Cryptography, the meaning of the message is
hidden, not its existence
– Kryptos = “hidden” in Greek
– Cryptography is the fundamental technique to counter
these threats because the outsider does not understand
the meaning of messages
♦ Cryptanalyst: Person working for unauthorized
interceptor
♦ Cryptographer: Person working for legitimate
sender or receiver
♦ Cryptology: Study of encryption and decryption,
including cryptography and cryptanalysis

5. 5
Modern Encryption Principles
♦ An encryption scheme has 5 ingredients
– Plaintext, Encryption Algorithm, Key, Ciphertext, and
Decryption Algorithm
– Security depends on secrecy of the key, not algorithm

6. Proposed Conceptual Framework
6

7. Selection of image area for
hiding textual data
♦ In this step we propose to insert the secret text on
the selected image. We have two basic
assumptions in this step:
– firstly, the sender and the receiver know which image is
being transmitted and
– secondly, the area in the image that is used for hiding
secret data. Selecting a proper portion in the image is a
very essential step because we are going to modify the
pixels in the spatial domain. After selecting a proper
portion in an image the text can be inserted.
7

8. Information hiding by modifying
image within the Spatial Domain
♦ In this step i propose to use:
♦ Replacing Least Significant Bit: The Embedding data is
hidden by replacing the least significant bit (LSB) of each
pixel in the cover image
8

9. Advanced Encryption Standard (AES)
♦ The Advanced Encryption Standard (AES) specifies a
approved cryptographic algorithm that can be used to
protect electronic data.
♦ The AES algorithm is a symmetric block cipher that can
encrypt (encipher) and decrypt (decipher) information.
♦ Encryption converts data to an unintelligible form called
ciphertext.
♦ Decrypting the ciphertext converts the data back into its
original form, called plaintext.
♦ The AES algorithm is capable of using cryptographic keys
of 128, 192, and 256 bits to encrypt and decrypt data in
blocks of 128
9

10. 10
There a four basic step, called layers, that are used to
form the rounds:
(1) The ByteSub (SB) Transformation: This non-
linear layer is for resistance to differential and
linear cryptanalysis attacks.
(2) The ShiftRow (SR) Transformation: This linear
mixing step causes diffusion of the bits over
multiple rounds.
(3) The MixColumn (MC) Transformation: This
layer has a purpose similar to ShiftRow.
(4) AddRoundKey (ARK) Transformation: The
round key is XORed with the result of the above
layer.

11. Decryption
Each of the steps Byte Sub, Shift Row, Mix Column, and
AddRoundKey is inversible:
(1) The inverse of Byte Sub is another lookup table, called
InvByteSub (IBS).
(2) The inverse of Shift Row is obtained by shifting the rows
to the right instead of to the left, yielding InvShiftRow
(ISR)
(3) The transformation InvMixColumn (IMC) is given by
multiplication by the matrix
(4) AddRoundKey is its own inverse.
11

12. AES Encryption Algorithm Flow
12

13. Basics of Modern
SteganographySteganography
13
fE: steganographic function "embedding"
fE-1: steganographic function "extracting"
cover: cover data in which emb will be
hidden
emb: message to be hidden
key: parameter of fE
stego: cover data with the hidden message

14. Steganalysis meets Cryptanalysis
♦ Knowing the steganography program used to hide
the message can be extremely handy when
attempting to reveal the actual hidden message
♦ Identifying and cracking the algorithm
– Unfortunately, some of these programs use strong
encryption 256-bit or stronger
♦ Reveal or Crack the password, seed, or secret key
– Practically all Steganography programs use a
password to hide the message
14

15. Steganalysis meets Cryptanalysis
Cryptanalysis
♦ As stated previously, in Steganography
the goal is to hide the message, NOT
encrypt it
♦ Cryptography provides the means to
encrypt the message
15

16. Steganography – Modern Day
16

17. Anomaly – Visual Detection
♦ Can you see a difference in these two
pictures?
17

18. Result Analysis
♦ If the encrption and decryption key is
wrong,then the output of hidden text will be
a display unknown text.
♦ To view original hidden message, keys or
password should be loaded correctly in both
encryption and decryption sides.
18

19. 19

20. 20
If the key or password loaded is wrong then
the output of the decrypted emmbedded text
will be wrong as follows in below simulation
analysis..

21. 21

22. Conclusion
♦ In this paper i proposed a new technique of
using image as a cover medium for
concealing cryptographic communication.
♦ This is a new technique, which can be used
to disguise the use of encrypted
communication as well as keep the hidden
information secret
22

23. 23