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Original Publication Date: 2001-Apr-13
Included in the Prior Art Database: 2001-Apr-13
Document File: 3 page(s) / 9K

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Yung Weng Fan: AUTHOR [+1]



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by Yung Weng Fan and Se Toh Wai Tuck


Phone cloning and illegal modification is a problem in many mobile phone markets throughout the world. Due to market segmentation and price discrimination strategies, the prices of a phone of the same make and model can vary greatly in different regions and countries.

Mobile phones are then bought from markets where they are cheaper (e.g., Europe) and re-exported to another market (e.g., China) where a higher selling price may be obtained for the mobile phone.

Such mobile phones are sold after they have modified to support local languages. To accomplish this an Asian Character Font Memory chip (CGROM) is installed in the mobile phone, and the mobile phone is reconfigured via Flexing.

There are two known methods of countering alleviating these problems. The first method is to create different PCB layouts for mobile phone models that are intended for sale in for example China.

For instance, non-Chinese market phones will not support CGROM in the layout. A separate PCB layout is created to cater for the CGROM. This method is costly and requires substantial engineering, manufacturing, and distribution effort.

The second method is to incorporate the Asian fonts into the same Flash memory that is used to store the code. This method makes cloning more difficult but does not prevent it.

A new method is described herein that may reduce the problem without incurring additional cost to the mobile phone.


Two existing hardware components are used in this new design. They are a IIM (IC Identification Module) and a Protection Register. The IIM consists of a 128-bits Unique ID register that is programmed to a unique value (UID) for each die produced.

It is laser programmed in the factory. Once programmed, it is not reversible. The IIM module is embedded in a Baseband IC in the mobile phone. The IIM register is readable by the micro controller unit (MCU) in the mobile phone.

The protection register is a 64-bits, lockable register in a Flash memory in the mobile phone. The process is irreversible. Once it is locked, the content of the flash memory cannot be changed.

The overview of the design is shown in Figure 1. A key generation process is implemented to generate a new 128-bits unique key from the UID (IIM). The new key will be used to identify the type of fonts (CGROM) supported by the phone.

This new key will be referred to as the Font Identification Key hereafter. The Font Identification Key generator can either be an encryption, convolution, or an orthogonal process. The objective is to create a unique and hidden key in every phone.

Since each phone has its own Font Identification Key, it will be difficult to crack. The UID (IIM) can be read by the MCU. Hence, it is not used as the Font Identification Key directly...