24-04-2010, 12:30 AM
Visual Cryptography
1. Introduction
Visual cryptography (VC) is a method of encrypting a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. Each participant holds a transparency. Most of the previous research work on VC focuses on improving two parameters: pixel expansion and contrast. In this paper, we studied the cheating problem in VC and extended VC. We considered the attacks of malicious adversaries who may deviate from the scheme in any way.
EVEN with the remarkable advance of computer technology, using a computer to decrypt secrets is infeasible in some situations. For example, a security guard checks the badge of an employee or a secret agent recovers an urgent secret at some place where no electronic devices are available. In these situations the human visual system is one of the most convenient and reliable tools to do checking and secret recovery. Therefore, Naor and Shamir [19] invented the visual cryptography (VC) in which a secret image (printed text, picture, etc.) is encrypted in a perfectly secure way such that the secret can be decoded directly by the human visual system.
1.1 Project Scope
1.2 This approach is applied for sending of any image secretly to receivers. Participant of out sider inserted fake shares or images are detected and corresponding participant is valid or not is verified.
In visual cryptography we propose three cheating methods and apply them on existent VC or EVC schemes. Although, the revealed secret is an image, our attacks are not like the attacks against watermarks, such as the Stir mark attack, which makes watermarks undetectable. Our attacks are to reveal fake images to cheat honest participants. Our attacks are more like the man-in-the-middle attack in cryptography. In fact, our attacks are very general for all kinds of VCSs without cheating-prevention mechanism. We propose three cheating methods against VC or EVC schemes.
2. Overall description
2.1 Product Perspective
Visual cryptography is a popular solution for image encryption. Using secret sharing concepts, the encryption procedure encrypts a secret image into the so-called shares which are noise-like secure images which can be transmitted or distributed over an untrusted communication channel. Using the properties of the human visual system to force the recognition of a secret message from overlapping shares, the secret image is decrypted without additional computations and any knowledge of cryptography.
2.2 Product Feature developer applications
This application discusses some of the concepts on which these systems are built. The Visual cryptography is modulated in to 5 main parts
¢ There is a login process for every participant to view the secret image.
¢ Encoding the image in to shares and send it to the participant.
¢ Decoding the image by stacking the ˜n™ shares or fewer than n i.e. ˜k™ shares where (k<=n).
¢ Verification is done by verifying the original share of the first participant with the verification share of the second participant.
¢ All GUI components are created using AWT Swings for user friendly.
2.3 User Classes and Characteristics
Using this product user can prevent the cheating in VCS from the intruders in sharing the original image from one participant to another.
The participant will first login to the window; it shows a message open the secret image.
Participant has to select the image and open the file, next it asks for the verification image to open.
We have to decode the process by adding the original image shares and verification image shares.
To verify whether the shares are genuine are not we have to stack the share1 of original image by verify2 of verification image for participant and vice versa for second participant.
if both participants have genuine shares the original image is opened.
2.4 User Documentation
In our user manual we are going to keep the information regarding our product, which can be understandable by a new person who is going to use it. If a new person is using it, online help will be provided in that. We are going to explain each and every step clearly about our product so that any user can easily understand it.
3. System Features
In this mechanism we have 5 modules
¢ Security & Login Module
¢ Encoding the Image
¢ Verification Module
¢ Decoding the Image
¢ User Interface & Manual
Security & Login Module
To provide security for the application we designed a login page so that unauthorized person cannot open the window.
Encoding the image
Here we are encoding by selecting the secret image and dividing the image in to shares i.e 2 shares, share1 & share2 and we are selecting the another verification image and dividing in to 2 shares as verify1 & verify2.
Verification Module
We have to verify the image by stacking the share1 of 1st participant and verify2 of 2nd participant we will get a verification image1 and flag1 is enabled and in the same way share2 of 2nd participant & verify1 of 1st participant is stacked together so that we will get the verification image2 and flag2 is enabled. After the flags are enabled if we click on them they display the messages as participant1 & 2 verifications are successful
Decoding the Image
After verifying the participants we have to stack the share1 & share2 and decode the secret image.
User Interface & Manual
This module is specially designed for the GUI components for the participant to interact with the window efficiently. Itâ„¢s a user friendly module.
4. External Interface Requirements
4.1 User Interfaces
This application include GUI standards or product family style guides that are to be followed, screen layout constraints, standard buttons and functions that will appear on every screen, error message display standards, and so on.
1. Introduction
Visual cryptography (VC) is a method of encrypting a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. Each participant holds a transparency. Most of the previous research work on VC focuses on improving two parameters: pixel expansion and contrast. In this paper, we studied the cheating problem in VC and extended VC. We considered the attacks of malicious adversaries who may deviate from the scheme in any way.
EVEN with the remarkable advance of computer technology, using a computer to decrypt secrets is infeasible in some situations. For example, a security guard checks the badge of an employee or a secret agent recovers an urgent secret at some place where no electronic devices are available. In these situations the human visual system is one of the most convenient and reliable tools to do checking and secret recovery. Therefore, Naor and Shamir [19] invented the visual cryptography (VC) in which a secret image (printed text, picture, etc.) is encrypted in a perfectly secure way such that the secret can be decoded directly by the human visual system.
1.1 Project Scope
1.2 This approach is applied for sending of any image secretly to receivers. Participant of out sider inserted fake shares or images are detected and corresponding participant is valid or not is verified.
In visual cryptography we propose three cheating methods and apply them on existent VC or EVC schemes. Although, the revealed secret is an image, our attacks are not like the attacks against watermarks, such as the Stir mark attack, which makes watermarks undetectable. Our attacks are to reveal fake images to cheat honest participants. Our attacks are more like the man-in-the-middle attack in cryptography. In fact, our attacks are very general for all kinds of VCSs without cheating-prevention mechanism. We propose three cheating methods against VC or EVC schemes.
2. Overall description
2.1 Product Perspective
Visual cryptography is a popular solution for image encryption. Using secret sharing concepts, the encryption procedure encrypts a secret image into the so-called shares which are noise-like secure images which can be transmitted or distributed over an untrusted communication channel. Using the properties of the human visual system to force the recognition of a secret message from overlapping shares, the secret image is decrypted without additional computations and any knowledge of cryptography.
2.2 Product Feature developer applications
This application discusses some of the concepts on which these systems are built. The Visual cryptography is modulated in to 5 main parts
¢ There is a login process for every participant to view the secret image.
¢ Encoding the image in to shares and send it to the participant.
¢ Decoding the image by stacking the ˜n™ shares or fewer than n i.e. ˜k™ shares where (k<=n).
¢ Verification is done by verifying the original share of the first participant with the verification share of the second participant.
¢ All GUI components are created using AWT Swings for user friendly.
2.3 User Classes and Characteristics
Using this product user can prevent the cheating in VCS from the intruders in sharing the original image from one participant to another.
The participant will first login to the window; it shows a message open the secret image.
Participant has to select the image and open the file, next it asks for the verification image to open.
We have to decode the process by adding the original image shares and verification image shares.
To verify whether the shares are genuine are not we have to stack the share1 of original image by verify2 of verification image for participant and vice versa for second participant.
if both participants have genuine shares the original image is opened.
2.4 User Documentation
In our user manual we are going to keep the information regarding our product, which can be understandable by a new person who is going to use it. If a new person is using it, online help will be provided in that. We are going to explain each and every step clearly about our product so that any user can easily understand it.
3. System Features
In this mechanism we have 5 modules
¢ Security & Login Module
¢ Encoding the Image
¢ Verification Module
¢ Decoding the Image
¢ User Interface & Manual
Security & Login Module
To provide security for the application we designed a login page so that unauthorized person cannot open the window.
Encoding the image
Here we are encoding by selecting the secret image and dividing the image in to shares i.e 2 shares, share1 & share2 and we are selecting the another verification image and dividing in to 2 shares as verify1 & verify2.
Verification Module
We have to verify the image by stacking the share1 of 1st participant and verify2 of 2nd participant we will get a verification image1 and flag1 is enabled and in the same way share2 of 2nd participant & verify1 of 1st participant is stacked together so that we will get the verification image2 and flag2 is enabled. After the flags are enabled if we click on them they display the messages as participant1 & 2 verifications are successful
Decoding the Image
After verifying the participants we have to stack the share1 & share2 and decode the secret image.
User Interface & Manual
This module is specially designed for the GUI components for the participant to interact with the window efficiently. Itâ„¢s a user friendly module.
4. External Interface Requirements
4.1 User Interfaces
This application include GUI standards or product family style guides that are to be followed, screen layout constraints, standard buttons and functions that will appear on every screen, error message display standards, and so on.
