Authentication using analog signal challenge

Abstract

Determining authenticity of a component in an imaging device includes generating an analog signal as an authentication challenge to the component. The component then generates a response to the authentication challenge by converting the analog signal into one or more digital values and capturing a derivative of the one or more digital values as the response. Authenticity of the component is determined by comparing the response with an expected response.

1 . In an imaging system having an imaging device and a supply item, each with a security device chip and having access to memory, a method of determining authenticity of the supply item installed and connected to the imaging device, comprising:
 generating in the imaging device an analog signal as an authentication challenge to the supply item;   transmitting the analog signal from the imaging device to the supply item;   receiving the analog signal at the supply item;   generating by the supply item a response to the analog signal by converting the analog signal into one or more digital values;   deriving by the supply item an arithmetic or logical derivative of the one or more digital values;   transmitting the response from the supply item to the imaging device;   receiving the response at the imaging device; and   comparing at the imaging device the response with an expected response stored in the memory of the imaging device to determine authenticity of the supply item.   
     
     
         2 . The method of  claim 1 , wherein the generating the analog signal includes generating a random analog signal. 
     
     
         3 . The method of  claim 2 , wherein the generating the random analog signal includes generating a signal that is random in at least one of amplitude, frequency, and duration. 
     
     
         4 . The method of  claim 1 , further comprising providing a toner cartridge as the supply item. 
     
     
         5 . The method of  claim 4 , further including providing the security device chip of the toner cartridge with first and second analog circuits. 
     
     
         6 . The method of  claim 1 , further including providing the security device chip of the imaging device with first and second analog circuits. 
     
     
         7 . The method of  claim 1 , wherein the transmitting and receiving occur over a shared bus between the security device chips of the imaging device and the supply item. 
     
     
         8 . The method of  claim 7 , further including configuring the shared bus as a two-wire serial bus with one wire of the two-wire serial bus carrying data between the security device chips of the imaging device and the supply item and the other wire of the two-wire serial bus carrying a clock signal between the security device chips of the imaging device and the supply item. 
     
     
         9 . The method of  claim 1 , further including a second supply item in the imaging device, the second supply item also having a security device chip in communication with the security device chips of the imaging device and the supply item. 
     
     
         10 . The method of  claim 9 , further including transmitting the analog signal to the security device chip of the second supply item from either the imaging device or the supply item and receiving the analog signal that the security device chip of the second supply item. 
     
     
         11 . The method of  claim 10 , further including generating by the security device chip of the second supply item a second response to the analog signal by converting the analog signal into one or more additional digital values and capturing a derivative of the one or more additional digital values. 
     
     
         12 . The method of  claim 11 , further including transmitting the derivative from the security device chip of the second supply item to said either the imaging device or the supply item from whence the analog signal was said transmitted. 
     
     
         13 . The method of  claim 12 , further including receiving the derivative at said either the imaging device or the supply item and comparing at said either the imaging device or supply item the derivative with a second expected response stored in the memory of the said either the imaging device of the supply item to determine authenticity of the second supply item. 
     
     
         14 . The method of  claim 1 , wherein the comparing the response with the expected response includes using a statistical correlation between the response and the expected response. 
     
     
         15 . In an imaging system having an imaging device and a supply item, each with a security device chip having first and second analog circuits and available memory, a method of determining authenticity of the supply item installed in the imaging device and having the security device chips of the imaging device and the supply item connected to one another, comprising
 by either of the security device chips of the imaging device or supply item, generating one or more random numbers;   identifying one or more parameters stored in the memory based on the one or more random numbers; and   by one of the analog circuits of said either of the security device chips of the imaging device or supply item, generating a random analog signal based on the one or more parameters and using the random analog signal as an authentication challenge to the other of said either of the security device chips of the imaging device or supply item.   
     
     
         16 . The method of  claim 15 , wherein the generating the random analog signal includes generating a signal that is random in at least one of amplitude, frequency, and duration. 
     
     
         17 . The method of  claim 16 , further including transmitting over a shared bus between the security device chips of the imaging device and the supply item the authentication challenge from said either of the security device chips of the imaging device or the supply item to said other of said either of the security device chips of the imaging device or supply item. 
     
     
         18 . The method of  claim 17 , by the security device chip of said other of said either of the security device chips of the imaging device or supply item, receiving the authentication challenge and by another of the analog circuits generating one or more digital values based on the random analog signal and capturing a derivative. 
     
     
         19 . The method of  claim 18 , further including providing a response based on the captured derivative and authenticating the security device chip of the supply item based on the response. 
     
     
         20 . The method of  claim 18 , wherein at least one of the analog circuits of both of the security device chips of the imaging device and supply item are operative to generate digital values from the random analog signal during a measurement interval beginning with a programmable start condition of said either of the security device chips.