Digital camera that incorporates an authentication arrangement for application to consumable print rolls

1. A digital camera that comprises

an image capturing assembly for capturing an image and generating image data;

processing circuitry connected to the image capturing assembly for receiving the image data, processing the image data and generating print data;

a printer that is connected to the processing circuitry to receive the print data, the printer being connectable to a consumable print roll to be validated, such that the processing circuitry is capable of communicating with the print roll, wherein

an authentication chip is connected to the processing circuitry and is configured to incorporate a random function that generates a random number when called by the processing circuitry and to apply a one-way function to the random number to generate a first value that is passed to the processing circuitry, the processing circuitry being configured to call a one-way function from the print roll that is configured to apply that function to the random number and to return a second value to the processing circuitry, the processing circuitry being further configured to compare the first and second values, thereby verifying the authenticity of the print roll.

2. A digital camera as claimed in claim 1 , in which the authentication chip stores a secret key and is configured to base the one-way function on the secret key.

3. A digital camera as claimed in claim 1 , in which the authentication chip is configured so that the random function generates a different random number for each invocation of the random function.

4. A method of verifying the authenticity of a consumable print roll for use with a digital camera that includes an image capturing assembly for capturing an image and generating image data, processing circuitry connected to the image capturing assembly for receiving the image data, processing the image data and generating print data,

a printer that is connected to the processing circuitry to receive the print data, the printer being connectable to the consumable print roll to be validated such that the processing circuitry is capable of communicating with the print roll, the method comprising the steps of:

calling a random function stored on an authentication chip of the camera to generate a random number;

calling a one-way function stored in the authentication chip and applying the one-way function to the random number to generate a first value;

calling a one-way function stored on the print roll and applying the one-way function to the random number to generate a second value;

comparing the first value to the second value; and

generating a result dependent on the comparison so as to verify the authenticity or otherwise of the object.

5. A method as claimed in claim 4 , in which the step of applying the one-way function of the authentication chip to the random number includes the step of applying the one-way function based on a secret key stored by the authentication chip.

6. A method as claimed in claim 5 , in which the step of applying the one-way function of the print roll to the random number includes the step of applying the one-way function based on a secret key stored by the print roll.

7. A method as claimed in any one of claims 4 to 6 , in which the step of calling the function stored by the print roll includes the step of calling the function stored by an authentication chip of the print roll.