transfer ownership from the company to the individual customer, who will start to pair with the thermostat that they bought. However, the lifecycle of the product moves on, for example when a house is sold, the thermostat is sold with it, so what happens to the certificate? This is where revoke and rotate come in. Revocation and renewal go hand in hand. If we simply revoke the certificate, the device is essentially dead. With a renewal system you can push a new identity to the thermostat and pair it with a new user. There is also another use case that illustrates the need for rotation. This is the short-term rental market, when we can imagine a door lock that needs to be opened by a renter for a week, following which, a different renter will need access. Ideally the owner of the house would want the different renters to have different passwords, which may need to change every week of the year. This is where certifi cate rotation can be used, synchronized to the calendar of the short-term rental companies to give that user experience. Everything is synchronized to how well you revoke and renew those certifi cates.
Once the attestation of that new keeper is done so that the new keeper can be trusted by the platform, thanks to the managed certifi cate chain, the chain of trust is preserved. The result is the generation of a new keeper that the device management platform can take over and control depending on their customer needs or customer requirements or the situation.
The Microchip ATECC608 TrustFLEX and another similar device the TA100 both address this device management use case. They also go beyond device management, offering secure authentication, secure boot and OTA verifi cation. The key attestation needs to be inside that secure boundary of the silicon, which allows key rotation because the keys are attested. There are also many other use cases of access or disposable authentication.
www.cieonline.co.uk.
Managing change
The above describes device management from the perspective of the secure element. The market sees the secure element as locked, allowing nothing to move, but this is not totally true. We can set policies to allow things to change in the confi guration. This is exactly how the TrustFLEX is confi gured. It allows those things to happen and the TA100 is probably even more powerful because of the variety of rights and permissions it can handle. If we look at challenges, there is a challenge of skills, - how do you implement that device management across the regions of the world? How do you implement device management during the prototyping phase, during the production phase? What happens when your product is released and what occurs after that?
When you want to remove the product from the market, you need to deactivate it, so a way is needed to terminate the usage of the product on the market. This allows companies to manage their warranties in a very controlled way, one that is better than just returning it with nobody knowing what happens to it afterwards. A company could apply a revocation at the time the device is returned to the store and then knows that that certifi cate is associated with a product that was a warranty return.
There is also the issue of acquisitions. If we imagine our thermostat company growing and acquiring another thermostat company, what happens to the fi rst certifi cate architecture. How do you grow it to acquire that next company? Device management services can help deal with these issues of scale. At Microchip, we would encourage our customers to implement device management for several reasons. Legislation standards, transfer of ownership, scalability and end-of- life of the product warranty are all drivers that are encouraging the market to adopt device management.
https://www.microchip.com/en-us/ Components in Electronics July/August 2023 33
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