The Colour Based Model

The basic shapes colour model is one of the members of the ‘fill based scheme’ developed in the conduct of this project. The fill based scheme is comprised of models in which fill types or elements (colours, patterns, gradients, etc.) are used as image properties to distinguish different sections of an image. In this implementation of the colour based model, after selecting the required grid size and number of steps for his login, as depicted in figure 4.3, the user clicks on the ‘continue’ button to go to the image properties window where he selects the properties he intends to use for each of his authentication steps. The user first selects the required properties for the first step and then clicks on the ‘next’ button to open the window for image properties selection for the second step and so on.

Fig. 4.4: image properties selection window (basic shapes colour)

Each image properties window has check boxes representing each of the properties provided by the authentication system (fig. 4.4). The properties for this system are: image background, image shape outline and image foreground (shape fill). The variants are the various colours to be chosen for each of these properties. Each property has a drop down menu with the list of variants for that property (fig. 4.4). The dropdown list of variants in this model shows the colours: black, white, blue, red, green and yellow for each of the properties used in the authentication model. The user first has to check the checkbox for each of the properties he intends to use for his password in the authentication step and then choose a variant of that property from the dropdown list of variants. The user may check any number of properties for his/her image in each step and select a variant for each property. For this work, the variants of adjacent properties cannot, however, be the same. If a user checks the checkbox for a given property but does not select a variant, the system assumes the default variant, which is ‘black’ in this model.

When the user completes the properties and variants selection consecutively for the desired number of steps and while in the properties and variants selection window for the last step, clicking on the ‘next’ button displays the message ‘user registered successfully’ as displayed in figure 4.5

For demonstration, suppose the user here chose a blue outline colour as the property for his pass image in any of the authentication steps (as depicted in figure 4.4), he only needs to locate and select the image with a blue outline colour for his authentication in that step. The ‘preview’ button provides an image preview from one of the images that satisfies his pass condition (property choice).

On closing the successful registration message box displayed in figure 4.5, the user is returned to the login window (Figure 4.2) where he can now authenticate as an existing user. The user enters his chosen username and clicks on the ‘sign in’ button. He is the presented with the authentication grid for the first step (as displayed on figure 4.6)

Fig. 4.6: Image selection grid for step 1 (basic shapes colour)

The authentication grid is a grid of size NxN depending on the grid size the user had selected in the registration phase. From the authentication grid, the user is expected to locate and click on the image containing the set of properties and variants (colours) he had selected in the registration phase. From the selection in figure 4.4, for this demonstration, the image the user needs to select for this step will need to have a ‘blue outline colour’. The only image that fits this appearance from the images in figure 4.6 is the image of a circle with a black fill colour, blue outline colour and yellow background colour. On selecting this image, the user receives the massage ‘Authentication Successful’ (figure 4.7) if this is his last authentication step, else the system automatically displays a new image grid for the selection of the image for the next authentication step.

One can observe that the image selection window also contains the step and attempt numbers displayed on the top left hand corner of the window. These are important and are there to inform the user of the exact authentication step he is on and the number of attempts he has made to authenticate. In a typical implementation, the system suspends the user’s account after three authentication attempts, to save the system from unauthorised access.

Three buttons are displayed on the lower side of each image selection window. The first button is the ‘abort’ button which allows the user to cancel the authentication process and return to the login window to re-enter his username and start the authentication afresh. The next button is the ‘Reshuffle’ button which allows the user to obtain a new image grid for that particular step. This is especially helpful when a user fails to identify the image with which to authenticate for that step. Ideally, the number of possible reshuffles per step is limited to one or two in each step. The last button is the ‘start over’ button. This button takes the user to the start of the authentication process. It allows him to start over the authentication with his current credentials by presenting him with the image grid for the first step of the authentication process and it allows him to start again from the first step. Unlike the ‘abort’ button that forces a user to re-enter his username, the ‘start over’ button allows him to start the authentication process from the first step. The essence of ‘start over’ button is to allow a user that remembers that he had been entering the wrong password go back and correct himself. The system does not regard a start over as a valid authentication since it has not been completed. However, since the system does not provide any clues to indicate that the user is on the right or wrong path to authentication, the button is not seen to pose any security risks.