Controlling access to device-specific information

A method for accessing to a device-specific function implemented in a device comprising:

• in a first mode, providing a first value to the device, and accepting a third value from the device, the third value being the device-specific function applied to a second value that is determined from the first value;
• in a second mode, providing the second value to the device, and accepting a fourth value from the device that depends on the third value;
• and
• preventing disclosure of the third value in response to providing the second value to the device.

A method for operating a device comprising:

• in a first mode, accepting a first value at the device, and providing a third value from the device, the third value being a device-specific function applied to a second value that is determined from the first value;
• in a second mode, accepting the second value at the device, and providing a fourth value from the device that depends on the third value;
• and
• preventing disclosure of the third value from the device in response to providing the second value to the device.

An integrated circuit comprising:

• first circuitry including second circuitry;
• the second circuitry implementing a device-specific function;
• and
• the first circuitry being configured to control access to the second circuitry, including being configured to permit verification of the device-specific function for one or more input values without permitting disclosure of the value of applying the device-specific function to the one or more input values.

An integrated circuit comprising:

• first circuitry configured to accept an input value and provide an output value, such that when a first value is input, a third value is output, the third value being the device-specific function applied to a second value that is determined from the first value;
• and
• second circuitry configured to accept an input value and provide an output value, such that when the second value is accepted as input a fourth value depends on the third value is provided as output;
• wherein the first and second circuitry are configured to prevent disclosure of the third value in response to the second value being provided to the circuitry.