Abstract: The present invention relates to multi-application, secure operating systems for small, secure devices, such as smart card microcontrollers. In particular, the present invention relates to mechanisms for secure runtime upload of applications onto small devices, authorisation mechanisms and the ability for authorised execution of multiple applications on the devices, where an application may be potentially larger than the microcontroller memory size. The mechanism simplifies life-cycle smart card management aspects related to post-issuance application (“applet”) upload and upgrade. Mechanisms to prepare applications (i.e. compiler techniques) using a common set of project files in one compiler toolset, for execution in a dual host & chip processor environment are described. These help automising the programming of the communication interfaces between the host and chip applications.

Abstract: Software code of a software program is executed in a multi-processor computer environment. The software code includes a first portion and a second portion. The first portion is executed in a computer. The second portion is executed in one or more tamper-resistant external devices which are in communication with the computer. The second portion includes a plurality of different blocks of code. At least some of the blocks have sequence data associated therewith. If sequence data exists in the current block of code to be executed in the one or more external devices, then the sequence data is used to determine if execution of the block of code is permissible or should be inhibited. The sequence data includes predecessor data and successor data.