Security device for camera sensor?

Question

I am currently designing a raspberry pi interface board and while I was looking at the documentation for MIPI CSI camera ports I bumped into this sentence:

Camera sensors supported by the official Raspberry Pi firmware are: the OmniVision OV5647, Sony IMX219 and Sony IMX477, no security device is required on Compute Module devices to use these camera sensors.

I tried to find information about this mysterious "Security device" required to operate a camera sensor, but I found nothing. Google didn't helped me much with "camera sensor security device chip"...

So, I am wondering what are these security devices?

Answer 1

I you look at the Raspberry PI Camera Module v2 schematic. You can notice the I2C bus is routed to two ICs: the IMX219 sensor and an ATSHA204A (Microchip CryptoAuthentication) (used to be from Atmel). On page 5 you can read this:

The device can also be used to validate (authenticate) a software/firmware module or memory storage element.

I suppose camera modules are considered sensitive elements. Since they are usually exposed in such a way a hacker could discreetly substitute them.

From another topic from Hackaday the following can be read:

But when you remove the ATSHA204A the board stops working. Which means it is meant to make sure the Pi Camera Drivers will not work with cloned boards unless they have a ATSHA204A with the correct secrets programmed in!

This topic also provide some information.