![]() ![]() This digest is then sent to the authentication chip as the challenge. #CALIBRE DOWNLOAD CHIP CODE#A hacker might be able to change the contents of the flash, but without knowing the secret, can’t generate a new validation value.ĭuring execution of the code in the boot ROM, the microprocessor generates in real time a digest of the executable program stored in the flash memory (see Figure 1). A hash algorithm such as Secure Hash Algorithm 1 (SHA-1) or SHA-2 is used to generate the program digest. This is computed by combining a digest of the program with a secret, a copy of which is stored in the authentication chip. Prior to system shipment, the OEM stores a validating value in the flash memory alongside the program. This boot ROM can be easily reprogrammed to work with an external authentication chip. System-on-Chip (SoC) devices often include a small boot ROM that contains the program used to initialize chip operation prior to executing the contents of the external flash memory. The second, anti-cloning, prevents unauthorized system builds or outright copies of the design. The first, secure boot, provides a way to ensure that only authentic programs are executed while still permitting upgrades to happen. #CALIBRE DOWNLOAD CHIP SOFTWARE#While these chips can be used in all sorts of ways to add security to a system, two software protection features are of particular interest. Depending on how securely the chip stores the secret, it can be very difficult to copy a personalized chip like this. The algorithm implemented inside the chip is chosen in such a way that an observer looking at the bus who can see both the challenge and the response can’t determine the value of the secret. The response is then sent back to the system. The system microprocessor sends a challenge to the chip, then the chip uses a cryptographic algorithm to combine the challenge with a secret that is securely stored in nonvolatile memory. The way these chips work is pretty straightforward. Hardware authentication chips, on the other hand, are turnkey devices that do not require internal programming or detailed knowledge of cryptographic algorithms and are modestly priced. Programmable, highly secure smart card processors have been available for some time but require additional firmware to be written and can add unacceptable costs to the system. Hardware security chips can help bring control back to the OEM. In the case of systems like medical devices, the OEM might even be exposed to liability concerns. If malware is downloaded into a system, the OEM’s reputation might be affected. It’s not just lost revenue to be worried about, however. The downside is that the OEM loses control over the contents of the flash, potentially allowing unauthorized copies or modification. This is great because it allows easy flash memory expansion and software modification, perhaps in the manufacturing line as a customer download or during a maintenance operation. Many systems use external standard flash memory chip(s) to store the operating program for processors that do not include embedded nonvolatile program storage. ![]()
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