Secure firmware update in embedded systems

Great numbers of embedded devices are performing safety critical operations, which means it is very important to keep them operating without interference. Update is the weak point that could be exploited by potential attackers to gain access to the system, sabotage it or to simply steal someone else's intellectual property. This paper presents an implementation of secure update process for embedded systems which prevents man-in-the-middle attacks. By using a combination of hash functions, symmetric and asymmetric encryption algorithms it demonstrates how to achieve integrity, authenticity and confidentiality of the update package that is sent to the target hardware. It covers implementation starting from key exchange, next explaining update package encryption process and then decryption on the target hardware. It does not go into a detail about specific encryption algorithms that could be used. It presents a generalized model for secure update that could be adjusted to specific needs.