the time of construction of the chip. Once constructed, the bit patterns stored in read-only memory cannot be altered. So, if the stored program that provides the instructions that the processor can execute is stored in that memory, then that program cannot be altered after the construction of the integrated circuit. With proper techniques, this form of construction allows to render the program stored in read-only memory at least very difficult to read and essentially impossible to modify without destroying the electronic module itself. From this property, the Subscriber Identity Module derives the intrinsic characteristics of tamper-resistant and tamper-evident. Taken together, these characteristics ensure a significant degree of trust in the code embedded in the SIM. So, from this position of trust, the SIM gains credence as a secure information storage platform and a secure computation platform. The operations that it provides are strongly protected from modification by forces external or internal to the electronic module. These two characteristics, secure information and secure program, give us what we can term a trusted computer platform. It is this characterization from which we will draw the direct connection of personal electronic devices to religion; both are seminally grounded in the concept and realization of trust. The subsequent implementation of a policy infrastructure, whether it is for a religion, or for a personal electronic device, is totally grounded in trust. The trust conveyed to the personal electronic device by the Subscriber Identity Module derives from: (a) a monolithic structure of processor and memory, (b) immutable code, (c) personal possession by the phone owner, and (d) a simple, well defined and highly constrained input/output channel. It should be a useful exercise to consider further these physiological features.

Since it is the trusted core of more than two billion cellular phones, the Subscriber Identity Module is designed for deployment in high volumes at low cost. It is intended to be placed inside the cellular phone and used to facilitate secure transactions as required and desired by the person and by the telephone system operator. It is a token that can, through a variety of identity authentication protocols, establish a strong likelihood that it is acting on behalf of the person using it. From these rather straightforward requirements, one can derive an applicable manufacturing technology for the construction of Subscriber Identity Modules: specifically, small size, low cost and high reliability. Meeting these requirements translates into using established computer technology whenever possible. Correspondingly, the central processing units used in Subscriber Identity Modules have tended to be technologies that are less powerful than the best central processing units at any specific point in time. However, for some specific functions, like special arithmetic operations needed for the most secure transactions, they are often more advanced than those central processing units. At the present time, high performance Subscriber Identity Module central processing units make use of internal bus structures that can address binary addresses that are 32-bits in length. They operate at very high clock speeds and consequently can obtain very high execution speed for programs that they run.

Computers require electrical power to function. The evolution of the computer in the electronic age has given us different schemes for providing power to the processor. These schemes bridge the expanse from large scale, fixed location computers to personal computers and then personal electronic devices.

The current incarnations of the Subscriber Identity Modules do not incorporate an on-card power source. Consequently, the power to run the electronic module of the SIM must be supplied by the phone. This obviously impacts the derived level of trust of the SIM.

If you look at the Subscriber Identity Module in your phone, you’ll find that there are 8 contacts showing on its surface. Two of these contacts are used by the phone to provide power to the chip; the others can be used for several functions, of which one is communication between the phone

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