July 2011

Doc ID 019008 Rev 1

1/5

AN3429

Application note

STM32 proprietary code protection overview

Introduction

Software providers are developing complex middleware solutions (Intellectual Propriety (IP)

code), which needs to be protected.

This IP code must be available as a plug-in in the end-user applications to build the

complete solution. The global protection mechanism limits access to it via a dedicated

application programming interface (API), while preventing any read access.

This application note provides an overview of the mechanism used to protect proprietary

code from possible read out by the end-user code, debugger tools or RAM Trojan code. This

mechanism provides a full API so the IP code can be easily called by the end-user

application and still be protected against direct access to the IP code itself.

The proposed solution is based on the MPU features and a special memory and peripheral

management mechanism from the end-user application and the IP code.

In the STM32 proprietary code protection method, two levels of protection are used:

●

Global Read Out Protection (Global ROP): IP code and end user code are protected

against direct reading (by debugger tools or RAM Trojan code) through STM32 ROP.

●

IP code Read Out Protection (IP ROP): IP code protected against end user code

(possible Trojan code) through the MPU.

As, once the global ROP is activated, the user no longer has full control of the Flash for

programming, the primary application (IP code) must also embed an IAP Layer. This IAP

allows loading the end-user application without compromising the protected code area.

For more details about the complete solution, please contact your local ST sales

representative.

www.st.com