Initially Posted A Little Less Than a Year Ago "An Exploration of ARM TrustZone Technology" Is A Good Technical Read

ARM TrustZone technology has been around for almost a decade. It was introduced at a time when the controversial discussion about trusted platform-modules (TPM) on x86 platforms was in full swing (TCPA, Palladium). Similar to how TPM chips were meant to magically make PCs "trustworthy", TrustZone aimed at establishing trust in ARM-based platforms. In contrast to TPMs, which were designed as fixed-function devices with a predefined feature set, TrustZone represented a much more flexible approach by leveraging the CPU as a freely programmable trusted platform module. To do that, ARM introduced a special CPU mode called "secure mode" in addition to the regular normal mode, thereby establishing the notions of a "secure world" and a "normal world".