1. A method for enabling a trusted execution environment (TrEE) in computing devices without a hardware trusted platform module (TPM) component, comprising steps for: retrieving an fTPM (firmware-based TPM) software module from a firmware component of a computing device, said fTPM providing a software-based interface to security extension functionality integral to one or more processors in the computing device; retrieving a software-based Monitor module from the firmware component of the computing device; instantiating the fTPM and the Monitor into a Secure World environment within protected memory of the computing device prior to booting an operating system (OS) on the computing device; wherein one or more of the processors use an ARM (advanced RISC machine)-based processor architecture, and wherein the security extension functionality integral to the ARM-based processors includes TrustZone-type security extensions and security primitives that are used by fTPM following instantiation of the fTPM; and enabling a TrEE on the computing device by allowing a Caller in a Normal World environment to access the security functionality of the one or more processors via a Secure Monitor Call to the Monitor, said Monitor then passing instructions relating to the Secure Monitor Call to the fTPM in the Secure World.