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MultiZone® Security SDK for Arm® Cortex®-M
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MultiZone® Security for Arm® Cortex®-M Processors

MultiZone® Security is the quick and safe way to add security and separation to your Arm Cortex-M processors. MultiZone software can retrofit existing designs. If you don’t have TrustZone, or if you require finer granularity than one secure world, you can take advantage of high security separation without the need for hardware and software redesign, eliminating the complexity associated with managing a hybrid hardware/software security scheme. Cortex-M legacy designs lack the physical resources to provide the necessary separation, thus leading to larger attack surface and increased likelihood of vulnerability. To shield critical functionality from untrusted third-party components, MultiZone provides hardware-enforced, software-defined separation of multiple equally secure worlds. Unlike traditional solutions, MultiZone is self-contained, presents an extremely small attack surface, and it is policy driven, meaning that no coding is required – or in fact even allowed.

MultiZone works with any Cortex-M0+, Cortex‑M3, Cortex‑M4, and Cortex‑M7 processors.

This version of the GNU-based SDK supports the following development boards:

SDK Installation

The MultiZone SDK works with any versions of Linux, Windows, and Mac capable of running Java 1.8 or greater. The directions in this readme are specific to a fresh installation of Ubuntu 18.04.4 LTS. Other Linux distros are similar.

Linux prerequisites

sudo apt update
sudo apt install make default-jre gtkterm

Note: GtkTerm is optional and required only to connect to the reference application via UART. It is not required to build, debug, and load the MultiZone software. Any other serial terminal application of choice would do.

GNU Arm Embedded Toolchain

Hex Five reference version: 8-2019-q3-update Linux 64-bit July 10, 2019

cd ~
tar -xvf gcc-arm-none-eabi-8-2019-q3-update-linux.tar.bz2

OpenOCD on-chip debugger

Hex Five reference build: GNU MCU Eclipse 0.10.0

cd ~
tar -xvf gnu-mcu-openocd-20190827.tar.xz

Linux USB udev rules

sudo vi /etc/udev/rules.d/99-openocd.rules

# STMicroelectronics ST-LINK/V2.1
SUBSYSTEM=="tty", ATTRS{idVendor}=="0483",ATTRS{idProduct}=="374b", MODE="664", GROUP="plugdev"
SUBSYSTEM=="usb", ATTRS{idVendor}=="0483",ATTRS{idProduct}=="374b", MODE="664", GROUP="plugdev"

# Atmel Corp. Xplained Pro board debugger and programmer
SUBSYSTEM=="tty", ATTRS{idVendor}=="03eb",ATTRS{idProduct}=="2111", MODE="664", GROUP="plugdev"
SUBSYSTEM=="usb", ATTRS{idVendor}=="03eb",ATTRS{idProduct}=="2111", MODE="664", GROUP="plugdev"

SUBSYSTEM=="tty", ATTRS{idVendor}=="0d28",ATTRS{idProduct}=="0204", MODE="664", GROUP="plugdev"
SUBSYSTEM=="usb", ATTRS{idVendor}=="0d28",ATTRS{idProduct}=="0204", MODE="664", GROUP="plugdev"

# CMSIS-DAP compatible adapters
ATTRS{product}=="*CMSIS-DAP*", MODE="664", GROUP="plugdev"

Reboot for these changes to take effect.

MultiZone Security SDK

cd ~

Build & load the MultiZone reference application

Connect the target board to the development machine as indicated in its user manual.

'ls bsp' shows the list of supported targets: ATSAME70 EKRA6M3 IMXRT1020 STM32F767.

Assign one of these values to the BOARD variable - default is STM32F767.

cd ~/multizone-sdk-arm
export GNU_ARM=~/gcc-arm-none-eabi-8-2019-q3-update/bin
export OPENOCD=~/gnu-mcu-openocd-20190827
make load

Run the MultiZone reference application

Connect the board UART port as indicated in its user manual.

Start the serial terminal console (GtkTerm) and connect to /dev/ttyACM0 at 115200-8-N-1

Hit the enter key a few times until the cursor 'Z1 >' appears on the screen

Enter 'restart' to display the splash screen

Hit enter again to show the list of available commands

      	             Hex Five MultiZone® Security                    
    Copyright© 2020 Hex Five Security, Inc. - All Rights Reserved    
This version of MultiZone® Security is meant for evaluation purposes 
only. As such, use of this software is governed by the Evaluation    
License. There may be other functional limitations as described in   
the evaluation SDK documentation. The commercial version of the      
software does not have these restrictions.                           
Implementer    : 0x41, Arm.
Variant        : 0x1, Revision 1.
PartNo         : 0xC27, Cortex-M7.
Revision       : 0x1, Patch 1.

Z1 > 
Commands: yield send recv mpu load store exec stats timer restart


Technical Specs

Up to 8 separated equally secure worlds – hardware-enforced, software-defined
Up to 16 memory-mapped resources per zone – i.e. flash, ram, rom, i/o, etc.
Scheduler: preemptive, cooperative, round robin, configurable tick
Secure interzone communications based on messages – no shared memory
Built-in trap & emulation for privileged instructions – SVC, MRS, MSR, CPS, WFE, WFI
Support for secure user-mode interrupt handlers mapped to zones – up to 128 sources
Support for Wait For Interrupt and CPU suspend mode for low power applications
Formally verifiable runtime ~2KB, 100% written in assembly, no 3rd-party dependencies
C library wrapper for protected mode execution – optional for high speed / low-latency
Hardware requirements: Arm Cortex-M0+/M3/M4/M7 processor w/ Memory Protection Unit
System requirements: 4KB for program, 2KB for data - CPU overhead < 0.01%
Development environment: any versions of Linux, Windows, Mac running Java 1.8

Additional Resources


Please remember that export/import and/or use of strong cryptography software, providing cryptography hooks, or even just communicating technical details about cryptography software is illegal in some parts of the world. So when you import this software to your country, re-distribute it from there or even just email technical suggestions or even source patches to the authors or other people you are strongly advised to pay close attention to any laws or regulations which apply to you. Hex Five Security, Inc. and the authors of the software included in this repository are not liable for any violations you make here. So be careful, it is your responsibility.

MultiZone is a registered trademark of Hex Five Security, Inc.

MultiZone is patent pending US 16450826, PCT US1938774.

Arm, Cortex, and TrustZone are registered trademarks of Arm Limited.

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