Visual Cryptography and BPCS Steganography for Data
Shielding
Prashant Lahane1, Yashashri Kumbhar2, Suraj Patil3, Swati More4, Meenali Barse5
Pune University, Department of Computer Engineering,
MIT College Of Engineering, Pune-38, India
ABSTRACT
The information is used for communication in
many applications which are in a secrete format.
Security is one of the most vital factors for
transferring different types of important
documents. For transfer of documents internet is
easy medium, it has wide range of applications.
But in reality the internet is not a secure form.
So we are suggesting use of VC method which
is simple, fast and provide security while
sharing secretes documents over the internet.
These documents are presented in a BMP
images. They are then extended it into two
encoded shares which can be transferred to the
receiver in a cover image using Bit Plane
Complexity Segmentation technology through
email. The segmentation method is used to store
data and data will be stored at higher
complexity. In steganography, data is hidden
into vessel image. Existing technique can hide
up to 15% of data amount of vessel image. But
hiding capacity of BPCS technique ranges up to
50 – 60%. Hence, the final image can be
obtained only when the shares are combined
together at receiving side. By using VC and
BPCS technologies together provides data
security to all forms of documents while
transferring over internet.
Keywords
VC (Visual Cryptography), Steganography,
vessel image, BPCS (Bit Plane Complexity
Segmentation), SI (Secrete Image), Information
Hiding, Encryption, Decryption, Complexity,
Bit plane, Segmentation.
INTRODUCTION
With the rapid improvement of network
technology,
multimedia
information
is
transmitted using the Internet easily. Various
confidential data such as military maps and
commercial identifications are transmitted over
the Internet. For transferring the documents
internet is used. So security is one of the most
important factors to be considered while
transferring different kinds of data. But in
reality internet is not secure medium because
one can easily hack confidential information in
document.
Due to the security problems of secret
images, various image secret sharing methods
have been developed. Visual cryptography is
introduced for the first time in 1994 by Noar and
Shamir [1]. Visual Cryptography is a special
encryption technique for providing security with
images. In this technique, using pixel expansion
method the Secret Image is expanded into
shares. So by overlapping shares original secret
image
can
be
obtained
back.Visual
cryptography scheme helps to eliminate
complex computation problem in decryption
process. Therefore visual cryptography is useful
for the low computation load requirement.
Steganography is another method
towards obtaining data security. The word
steganography has Greek origin. It means
“Covered Writing”. Steganography is technique
of data hiding technique in which secret data is
hidden into vessel image. The hiding capacity of
steganographic technique ranges up to 50 –
60%. A Stego-key is used to control the hiding
process for restricting detection and/or recovery
of the embedded data. LSB is one of the
techniques of steganography in which important
information is stored at LSB position. So
anyone can detect data easily. Capacity of data
vessel is nearly 5-10%.
So we invented new technique and this
technique is called Bit Plane Complexity
Segmentation (BPCS) Steganography which is
used to hide secret information in the form of
color image. It will store large amount of
information in the image. The data is stored in
highly complicated regions or segments. Hence
due to this maximum data storage, it is feasible
for using it in information security. For this
BPCS
BMP
image
format
is
compatible.Therefore, the final image can be
obtained only when the number of shares is
combined together on the receiving end. Thus
using a combination of VC and BPCS
technology provides data security to all forms of
documents during transfer over internet.
too. The performance measures of visual
cryptography method totally depends on
contrast, security, pixel expansion algorithm,
accuracy in the shares generation, computational
complexity, generated shares are significant or
not significant, types of images (either
monochrome or 24-bit image) and number of
secret images(either single or multiple)
encrypted by the VC algorithm. Visual
cryptography scheme is used to divide the image
into two parts such as each pixel is divided in to
two using pixel expansion algorithm and these
two parts of secret image are called as shares.
Black and white image: each pixel divided in 4
sub-pixels
White pixel: shared into two similar sub-pixel
layouts
Black pixel: shared into two corresponding
opposite (complementary) sub-pixel layouts.
RELATED WORK
Least Significant Bit Steganography and
Cryptography. Wilscy proposed improving the
Reliability of Detection of LSB Replacement
Steganography. Mangarao , proposed a Secure
and
Image Steganography with
LSB
Replacement Methods Using Image Contrast
scheme.
Capacity of vessel using LSB method is just 1020%. Also by using the LSB algorithm the
graying effect in the cover image still remains.
Main -drawback of LSB technique is hacker can
detect data in the cover image so easily. So Noar
and Shamir introduced Visual Cryptography
which uses pixel expansion algorithm. So this
new cryptographic scheme which can decode
concealed images without any cryptographic
computations. But all above schemes supports
only less number of image hiding, which results
into image distortion means the real image may
be widen or stretched.
Fig1: Visual Cryptography
For Perfect Security
-Layout was randomly chosen
-pixels have two black and white sub-pixels for
pixel expansion so that we can exclude pixel
distortion.
3. PROPOSED SCHEME
3.1. Visual Cryptography
In 1994, Naor and Shamir presented a new
cryptographic paradigm based at the pixel level.
They termed this as visual cryptography (VC)
and used this visual cryptography method to
encrypt text notes, pictures, videos, some voice
Fig 2: Visual Cryptography
• If the pixel is black
=
+
• If the pixel is white
=
+
Fig 3: Architecture of VC and BPCS
So like this there are 16 possible combinations
of pixel expansion for each white and black
pixel and algorithm of visual cryptography will
choose any random one to expand the pixel.
3.2.
BPCS
(Bit
Plane
Complexity
Segmentation)
Eiji Kawaguchi and Richard O introduced
BPCS steganography technique. For overcome
the short comings of traditional steganography
techniques such as Least Significant Bit (LSB)
technique, masking technique this BPCS is very
ideal. Previously Least Significant Bit (LSB)
technique has limited information-hiding vessel
capacity like 10-15%.But after applying BPCS
technique 60-65% Data can be hidden. This
technique is called Bit Plane Complexity
Segmentation
(BPCS)
Steganography.
Characteristic of scotopic vision is used in
BPCS technique. In BPCS technique, the cover
image is divided into region/blocks according to
the complexity value of block using
segmentation technique and the secret data is
hidden in noise blocks means blocks with high
complexity of vessel image without damaging
the image quality. In LSB technique, data is not
hidden in whole bits but it is stored only in the
last LSB bits. But in BPCS technique, data is
hidden in most significant bit (MSB) means all
the bits of the bit planes, provided secret data is
hidden in complex region.
• In Visual cryptography and as well as in Bit
Plane Complexity Segmentation BMP format
images are used because BMP image can store a
large amount of data and BMP image format is
also simple to develop for programmer it is easy
to read and have less header value. By using
conversion algorithm we first convert the secret
text in to secret BMP monochrome image and
use this secret image as input to visual
cryptography and we make two shares of this
secret image. Again we apply BPCS on those
shares means take 24-bit BMP color image as
input in BPCS and, make bit planes of this color
image and then again by applying the
segmentation on each bit plane we calculate
complexity of each block. According to the
complexity value we store our secret share in
those blocks which are having complexity value
more than threshold value. Threshold value
means we can give any value so as to store data
in the respective segments. Threshold value is
needed when most important data is to be sent
so we can store data in segments those are
having high complexity value that is high
complexity value proportional to high security.
Send these cover images via Emails to the
receiver, at receiver side same complementary
operations are done to retrieve data means
decryption process is done. Confidential
communication between organizations and
secret data storing. A business transaction that
does not have be licked. Data alteration is also
protected e.g. military message that should not
be changed by hackers. It is really hard for
hackers to eavesdrop the bank transactions. E.g.
Security codes can be shared with protection
these are the applications of this technique.
Method of doing BSCS
• Take 24-bit image as input and one share that
we want to hide behind the 24-bit image.
This is
24-bit
colour
image
• Read the image and covert byte data into bit
data and then make 24 bit planes of the image.
• Then make segments of all the bit planes.
Calculate complexity of each segment.
• And store share in that.
0
• The aim of BPCS steganography technique is
to Store secret messages inside a cover image in
a way that does not allow any "enemy" to even
detect that there is a secret message present.
Due to this technique there is no data alteration.
Randomization of bits so as that it is nearly
impossible for hacker to restore information,
and as well large amount of information can be
hidden 60-65% of vessel.
3.3. Calculating the Complexity
Segmentation tells us about in which block we
should store data according to complexity value.
Data will be stored in highly complex segments.
Here using BPCS technology we use 24-bit
color image. The image is of 54 byte header
format which is divided in to number of bit
planes. Bit plane is a group of bits of particular
position of particular color. For example,
consider bit plane 0 of red color and divide the
pixel into RGB format which are of 8-bits for
each color means total 24 bits. We apply
segments algorithm on each bit plane and then
calculate the complexity of segment.
Complexity of Segment= (Number of bit change
in block of bit plane)/(number of bits in the
block of bit plane)
7
Bit
plan
e
0
23
15
Bit
plane
1
Bit
pla
ne
2
Fig 4: Making bit planes from color image.
Conclusion
In this way we conclude that, we have presented
a feasible solution for Image Steganography that
takes the advantage of segmentation method by
which we can find the position of the bits and
retrieve data from the bit plane.It also makes use
of complex mathematical calculations which
bring down the computational time very less
making it a very effective method for Image
Steganography.
Results
• It can be very useful if can install it on web.
Means if we make it web based then there will
be no need of installing application on every
computer.
• By increasing the threshold value we can
increase the security of data. We can also
decrease the image distortion and greying
effects.
References
[1] Information Hiding Using Least Significant
Bit
Steganography
and
Cryptography,
Shailender Gupta,Ankur Goyssal, June 2012
[2] Department of Applied Math and Computer
Science, Weizmann Institute, Rehovot, 76100,
Israel.
e-mail: {naor,shamir}@wisdom.weizmann.ac.il.
[3] IMPROVING THE RELIABILITY OF
DETECTION
OF
LSBREPLACEMENT
STEGANOGRAPHY Shreelekshmi , Wilscy
and C E Veni Madhavan, October 2010.
[4] A Secure and Lossless Adaptive Image
Steganography with Mod-4 LSB Replacement
Methods Using Image Contrast, K. Devi
Lavanya, Nittala. Raviteja, Katta. Mangarao,
January 2014.