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Freescale Semiconductor
Application Note
© Freescale Semiconductor, Inc., 2012, 2013. All rights reserved.
1 Introduction
1.1 Purpose
The purpose of this application note is to explain how to
perform a secure boot on i.MX28 applications processors
with High Assurance Boot version 4 (HAB v4). This
includes steps on how to generate signed images and
configure the IC to run securely using freely available tools
provided by Freescale.
Executing trusted and authentic code on an applications
processor starts with secure boot provided by the on-chip
boot ROM. The i.MX family of applications processors
provides this capability with the High Assurance Boot
(HAB) component of the on-chip ROM. HAB provides
services to the ROM to authenticate software that executes
immediately after ROM, which is usually a bootloader, using
Document Number: AN4555
Rev. 1, 05/2013
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. i.MX28 security architecture overview . . . . . . . . . . . . 4
3. Designing for code signing . . . . . . . . . . . . . . . . . . . . . 8
4. Signed U-Boot and Linux kernel example . . . . . . . . 17
5. Encrypted boot and Elftosb . . . . . . . . . . . . . . . . . . . . 22
6. Manage the electrical fuses . . . . . . . . . . . . . . . . . . . . 23
7. Development and debug tips . . . . . . . . . . . . . . . . . . . 25
8. Example CSF text files for reference . . . . . . . . . . . . 26
9. Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Secure Boot with i.MX28 HAB Version 4
