Sethulakshmi II.Earlier methods used: A. Black And White Visual

 

 

 

 

Sethulakshmi Unnikrishnan

Department of Computer Science and
Technology Adi Shankara Institute of Engineering and Technology, Kalady
Kerala,India Email:[email protected]

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I.Abstract:

 

In
the art of visual cryptography, many shares are generated which are illogical
containing certain message within themselves. When all shares are piled
jointly, they tend to expose the secret of the image. The notion of visual
secret sharing scheme is to encrypt a secret image into n illogical share
images. It is unable to reveal any data on the original image if at least one
of the shares is not achieved. The original image, in fact, is realized by
overlapping the entire shares directly, in order that the human visual system
is competent to identify the collective secret image without employing any
complicated computational tools. Therefore, they are communicated steadily as
number of shares. The elliptic curve cryptography approach, in turn, is employed
to augment the privacy and safety of the image. The new-fangled technique is
utilized to generate the multiple shares which are subjected to encryption and
decryption.

 

 

 

II.Earlier methods used:

 

A. Black And White Visual Cryptography Schemes

 

Naor and Shamir’s proposed an
encryption scheme to convert a binary image into two shares. In this scheme
each share pixel p is encoded into two white and two black pixels each share
alone gives no clue about the pixel p whether it is white or black. Secret

 

 

Ms.Divya D

Department of Computer Science and
Technology

Adi Shankara Institute of
Engineering and

 

Technology, Kalady Kerala,India

Email:[email protected]

 

 

 

 

 

 

 

image is visible only when both
shares are stacked on each other. Visual secret sharing schemes based on the
Threshold value of mixed XOR and OR operation with reversing and based on
binary linear error- correcting code 2

 

The main disadvantage of this
schemes is that it can only be used for one set of confidential messages can be
embedded, therefore for large amounts of confidential messages several shares
have to be generated.

 

B. Color Visual Cryptography Schemes

 

Until the year 1997 visual
cryptography schemes were applied to only black and white images. First colored
visual cryptography scheme was developed by Verheul and Van Tilborg . A colored
secret images can be shared with the concept of arcs to construct a colored
VCS. In colored VCS one pixel is converted into m subpixels, and each subpixel
is further divided into c color regions. In each subpixel, there is exactly one
color region is colored, and other color regions are black. The color of one
pixel depends on the interrelations between the stacked subpixels. 3

 

This scheme offers a perfect
reconstruction while producing shares with size smaller than the size of input
image using maximum separable distance. This scheme provides pixel expansion
less than one.