An image stenography method that is difficult to reverse based on Pixel Value Differencing and Modulus Function

1. Image Steganography
Method Based on PVD and
Modulus Function
Image Processing Project

2. Abstract
● The traditional steganography methods with Pixel Value Differencing
usually only deal with the PVD in the horizontal direction but ignore the
vertical one.
● In this paper, the cover image is divided into 2×2 non overlapping blocks,
then the modulus function method is used in horizontal direction and the
simple PVD method is used in vertical direction for steganography.
● In addition, the falling-off-boundary problem is solved.
● Experimental results show that the proposed approach provides higher
stego-image quality, larger embedding capacity, and can against common
attacks.

3. The problem
● PVD (Pixel Value Differencing), uses the difference value of two adjacent
pixels of cover image to determine the number of bits that could embed
into the cover image
● This method has low embedding capacity, poor stego image quality and
also low security.

4. The solution
STEGANOGRAPHY
METHOD
BASED ON
PVD AND
MODULUS
FUNCTION

5. ● Existing Methods
Original Method
of PVD
● The cover image is divided
into non- overlapping blocks.
● Denote the pixel pair in some
block as P i and P j ˈthe
difference d is calculated as
d=P j − P i
● This range is divided into r
sub-regions R k (k=1,2,..,r), the
width of each sub-region are
power of 2. The number of
bits embedding in the region
of R k is n = log 2 ( w k ) ,
where w k is the width of the
k-th sub-region.
A method of PVD based
on modulus function
Improved PVD method
based on horizontal
and vertical direction
● The cover image is divided into non-
overlapping blocks, b is the decimal
value of secret information,
calculate:
● F rem = ( p i + p j ) mod(2 )
● When extract the secret information,
first of all , calculate the number of
bits each pixel can be embedded
● n = log 2 ( w k ) , then using
equation (1) to calculate the
decimal value of the embedded
information, and finally change the
decimal value F rem to n bits secret
message.
● 2 × 2 pixel blocks, two pairs
of horizontal direction’s
pixels and a pair of vertical
direction’s pixels.
● In order to extract the
secret information correctly,
a modification to another
pair of vertical direction’s
pixels is needed; if there
has falling-oơ-boundary
problems, the value of
pixels will have to be
adjusted.

6. Embedding Process
Let the original cover image from left to right, from top to bottom into non-
overlapping blocks with 2 × 2 pixels.
For an image with M×N (length and width), we can get blocks nblocks = M/2 X N/2
blocks.
Then a series of steps occurs to embed the hidden image into the original image
The Extraction process work exactly opposite to the embedding process to obtain the
original image.

7. Experimental Analysis

8. Experimental Analysis

9. Conclusion
This paper presents an image steganography method which utilize horizontal pixels and vertical pixel difference,
in the horizontal direction we use high-quality model function method for two pairs of pixels to embed message
and in the vertical direction we select one pair of pixels to embed message with the common PVD methods.
Experiments show that this scheme has not only improved the embedding capacity, stego image quality, but also
achieved high security such as resistance to common attacks and RS histogram attack