By: Steve Jarmusz
An accessory could be really anything that works with a host or base system. It could be a power charger, pair of speakers, cable, or as I mentioned, anything. There are number of reasons why you would want to authenticate your accessories, to guard them against cloning and counterfeiting. You may want to protect your brand or company’s reputation. Apple does this with the “MFI” policy that they have initiated. You might want to protect customer safety. Having a cloned surgical instrument or medical device that does not possess the same quality as the authentic product could be risky. There have been a number of cases publicized where the cloned product does not perform as well as the original. A battery in cell phones and portable devices is one that comes to mind. You can get really cheap knockoffs on E-Bay, but they may not last or have the storage capability as the OEM versions. There are a number of authentication schemes that could be used to perform the accessory authentication sequence. The most popular method that we have found is the Random Challenge Response method.
By adding an Atmel ATSHA204 CryptoAuthentication device to the host, the system is able to generate a Random Challenge for the client on the fly. In addition, by generating the challenge internally with the host’s ATSHA204 device, the response is unknown to the system, allowing the use of an unsecured processor without the threat that an attacker will be able to learn the system secrets. This dramatically limits the ability of an unauthorized device from producing the correct response. You could also do this without a hardware device on the host, but the downside is less security. Security is also very critical in many other applications. To learn more, check out this white paper on the technology and various use cases.