Now that we have addressed basic cryptography and cryptographic modules, it is necessary to delve into the topic of cryptographic key management. Cryptographic modules can be considered cryptographically secured islands in larger systems, each module containing cryptographic algorithms, keys, and other assets needed to protect sensitive data. Deploying cryptographic modules securely, however, requires secure key management. Planning key management for an embedded device and/or full scale IoT enterprise is essential to securing and rolling out IoT systems. This requires organizations to normalize the types of cryptographic material within their IoT devices and ensure they work across systems and organizations. Key management is the art and science of protecting cryptographic keys within devices (crypto modules) and their interactions across the enterprise. It is an arcane technical discipline that was initially developed and evolved by the US Department of Defense long before most commercial companies had an inkling of what it was or had any need for cryptography in the first place. Now, more than ever, it is a subject that organizations must get right in order to secure connected things in our world.
The fallout from the Walker spy ring led to the creation of many of the key management systems and techniques widely used by the Department of Defense (DoD) and NSA today. Starting in 1968, US Navy officer John Walker began selling classified cryptographic key material to the Soviet intelligence services. Because this internal compromise was not discovered for many years (he was not caught until 1985), the total damage to US national security was severe. To prevent crypto key material being compromised and maintain a highly accountable system of tracking keys, various DoD services (the Navy and the Air Force) began creating their own key management systems that were eventually folded into what is today known as the NSA's Electronic Key Management System (EKMS). The EKMS is now being modernized to be more network-centric and have distributed architectures (https://en.wikipedia.org/wiki/John_Anthony_Walker).
The topic of cryptographic key management is frequently misunderstood, often more so than cryptography itself. Cryptography and key management are siblings; the security provided by each depends enormously on the other. Key management is often not implemented at all or is implemented insecurely. Either way, unauthorized disclosure and compromise of cryptographic keys through poor key management renders the use of cryptography moot. Necessary privacy and assurance of information integrity and origin are lost.
It is also important to note that many of the cryptographic services you use today, namely PKIs, are key management systems. Regarding the IoT, it is important for organizations to understand the basic principles of key management because not all IoT devices will interact with and consume PKI certificates (that is, be able to benefit from third-party key management services). A variety of other cryptographic key types—symmetric and asymmetric—will be utilized in the IoT whether it's administering devices (SSH), providing cryptographic gateways (TLS/IPSec), or just performing simple integrity checks on IoT messages (using MACs).
Why is key management important? Disclosure of many types of cryptographic variables can lead to catastrophic data loss even years or decades after the cryptographic transaction has taken place. Today's internet is replete with people, systems, and software performing a variety of man-in-the-middle attacks, ranging from simple network monitoring to full-scale nation state attacks and compromises of hosts and networks. One can collect or re-route otherwise encrypted, protected traffic and store it for months, years, or decades. In the meantime, the collectors can clandestinely work for long periods of time to exploit people (human intelligence, as in John Walker) and technology (this usually requires a cryptanalyst) to acquire the keys that were used to encrypt the collected transactions. Within IoT devices, centralized key generation and distribution sources or storage systems, key management systems, and processes perform the dirty work of ensuring cryptographic keys are not compromised during machine or human handling.
Key management addresses a number of cryptographic key handling topics pertinent to the devices and the systems in which they operate. These topics are indicated in the following relational diagram:
