Bernardo Rodrigues
Dec 30, 2019 · 7 min read

IOTA Masked Authenticated Messaging on OpenSTLinux of STMicroelectronics Discovery Kit

This is the third tutorial on my series of IOTA based projects on OpenEmbedded hardware. It is another Proof of Concept meant to show the exciting possibilities that the meta-iota OE layer create.

This time I decided to move in the direction of Industrial IoT Hardware. STMicroelectronics is a leading Integrated Device Manufacturer delivering solutions that are key to Smart Driving, Smart Industry, Smart Home & City and Smart Things. The IOTA Foundation recenlty published “IOTA Links with STMicroelectronics to Accelerate IoT Technology Integration”. The cornerstone of this cooperation was the integration of the IOTA Tangle into STM32Cube expansion software for the industry-leading STM32 32-bit MCU (Cortex-M*) ecosystem, the X-CUBE-IOTA1. And now meta-iota is adding a new path for this collaboration, for the OpenSTLinux side of things. OpenSTLinux is a Linux distribution based on the OpenEmbedded build framework, and you can find information about it on its official OpenSTLinux Wiki.

So let’s talk about the hardware. The STM32MP157C-DK2 Discovery Kit leverages the capabilities of STM32MP1 Series microprocessors to allow users easily develop OpenSTLinux applications for the ARM Dual Cortex A7 main processor, as well as STM32CubeMP1 software for the Cortex M4 coprocessor. While the X-CUBE-IOTA1 toolkit is useful for the M4 coprocessor, we’re going to focus on the OpenSTLinux of the Cortex A7.

STMicroelectronics STM32MP157C-DK2 Discovery Kit

For this Proof of Concept, we’re going to send Masked Authenticated Messages (MAM) from OpenSTLinux into the Tangle. We will use the MAM examples provided in the EnTangle’d repository, although I’m hosting them in my own repository to ease the integration into its BitBake recipe.

MAM is the result of a research collaboration between the IOTA Foundation and the Belarusian State University (BSU). In a nutshell, MAM acts as a second layer data communication protocol that adds functionality to send and receive encrypted data streams over the Tangle. MAM aims at the important need for integrity and privacy in the IoT industry because how the IOTA consensus protocol encapsulates those message streams. For more in-depth explanations of MAM, please refer to:

For this tutorial we will take a different workflow, when compared to the previous ones. Instead of building a whole image, we will use the stock distribution provided by ST with the board. It already contains a prebuilt image of the OpenSTLinux distribution. You can also download it from ST’s website and flash it into the SD card. We will build .deb packages of entangled-mam-examples and its dependencies, and install them on the OpenSTLinux environment.

Preparing the STM32MP157C-DK2 board

When you purchase the STM32MP157C-DK2 board, it comes with an SD Card pre-flashed with OpenSTLinux. But you can always follow the steps described in the Getting Started section of the STM32 MPU Wiki to get OpenSTLinux installed in the SD Card of the board.

Start by connecting minicom to the /dev/ttyACM0 device so you can interact with the board via UART through the ST-LINK/V2–1 cable (microUSB). Make sure the board has an Ethernet cable connected to your LAN router. After turning the board on, wait until Linux finishes booting up, and then find out the board’s local IPv4 address with the ifconfig command (look for eth0 device). In my case, it’s

BitBaking the .deb packages

Now we’re going to use BitBake to generate .deb packages of entangled-mam-examples and its dependencies. We’re going to set everything up so the resulting packages are matching with the OpenSTLinux distribution running on the board, so we can install them with the dpkg package manager.

1. Prepare your workstation for Yocto/OpenEmbedded development. Refer to Yocto’s official documentation for more details on setting up.

Assuming you are using Ubuntu 18.04:

$ sudo apt-get install sed wget curl cvs subversion git-core coreutils unzip texi2html texinfo docbook-utils gawk python-pysqlite2 diffstat help2man make gcc build-essential g++ desktop-file-utils chrpath libxml2-utils xmlto docbook bsdmainutils iputils-ping cpio python-wand python-pycryptopp python-crypto libsdl1.2-dev xterm corkscrew nfs-common nfs-kernel-server device-tree-compiler mercurial u-boot-tools libarchive-zip-perl ncurses-dev bc linux-headers-generic gcc-multilib libncurses5-dev libncursesw5-dev lrzsz dos2unix lib32ncurses5 repo libssl-dev

2. Clone and initialize the repositories for OpenSTLinux. We are using Google’s repo tool for that:

$ mkdir ${HOME}/stm32
$ cd ${HOME}/stm32
$ repo init -u -b refs/tags/openstlinux-4.19-thud-mp1-19-02-20 && repo sync
$ ls layers/
meta-openembedded meta-qt5 meta-st meta-timesys openembedded-core

3. Clone meta-iota into the layers subdirectory:

$ cd ${HOME}/stm32/layers
$ git clone
$ ls
meta-iota meta-qt5 meta-timesys
meta-openembedded meta-st openembedded-core

4. Start the build environment:

$ cd ${HOME}/stm32/
$ DISTRO=openstlinux-weston MACHINE=stm32mp1-disco source layers/meta-st/scripts/

5. Add meta-iota to the BASELAYERS variable of conf/bblayers.conf. This will inform BitBake that we will also work with the meta-iota layer.

${OEROOT}/layers/meta-openembedded/meta-oe \
${OEROOT}/layers/meta-openembedded/meta-gnome \
${OEROOT}/layers/meta-openembedded/meta-xfce \
${OEROOT}/layers/meta-openembedded/meta-initramfs \
${OEROOT}/layers/meta-openembedded/meta-multimedia \
${OEROOT}/layers/meta-openembedded/meta-networking \
${OEROOT}/layers/meta-openembedded/meta-webserver \
${OEROOT}/layers/meta-openembedded/meta-filesystems \
${OEROOT}/layers/meta-openembedded/meta-perl \
${OEROOT}/layers/meta-openembedded/meta-python \
${OEROOT}/layers/meta-iota/meta-tangle \

7. Start building the entangled-mam-examples package:

$ bitbake entangled-mam-examples

Grab a coffee and watch BitBake do its magic. This will probably take a while.

8. Copy the packages from tmp-glibc/deploy/deb/cortexa7t2hf-neon-vfpv4 to the board (entangled-mam-examples and its dependencies):

$ cd tmp-glibc/deploy/deb/cortexa7t2hf-neon-vfpv4
$ scp entangled-mam-examples_git-r0_armhf.deb \
libcjson1_1.7.10-r0_armhf.deb \
libhttp-parser2.8_2.8.1-r0_armhf.deb \
mbedtls_2.13.0-r0_armhf.deb \

9. On the ssh connection with the board, install the packages into OpenSTLinux with the dpkg utility:

# dpkg -i libcjson1_1.7.10-r0_armhf.deb
# dpkg -i libhttp-parser2.8_2.8.1-r0_armhf.deb
# dpkg -i mbedtls_2.13.0-r0_armhf.deb
# dpkg -i entangled-mam-examples_git-r0_armhf.deb

Running the MAM examples on OpenSTLinux

It’s finally time to run the MAM examples on OpenSTLinux! Run the following commands on the ssh connection with the board.

1. First, let’s create a disposable random seed. Remember, this is just an illustrative example! Seeds should never be exposed in plaintext, source code, or command line history! This example code is just meant to show how the MAM library is used, and real production scenarios must handle seeds with the appropriate security measures.

# cat /dev/urandom |tr -dc A-Z9|head -c${1:-81}

2. Let’s run the send-header example. This command will send a header, meaning it will declare a new message. These are the parameters that the executable expects:

# iota_mam_send_header 
usage: send-header <host> <port> <seed> <msg_public_key_type> (0 - on channel, 1 - on endpoint, 2 - announce channel, 3 - announce endpoint)

So let’s use as host (node address), 14265 as port (HTTP API), ARDNWTPEAYOYQRDYPUACNWIWZPP9AHADVAJEAUBKDTLDMMHRNTLLHCSN9ODRFL9PHBTWQAXICOPS9YBII as seed, and 0 for public key type.


3. Now, let’s run the send-packet example. This command will send a packet to the message we created with the previous send-header example. These are the parameters that the executable expects:

# iota_mam_send_packet 
usage: send-packet <host> <port> <seed> <msg_id> <payload> <last_packet>

So let’s use as host, 14265 as port, ARDNWTPEAYOYQRDYPUACNWIWZPP9AHADVAJEAUBKDTLDMMHRNTLLHCSN9ODRFL9PHBTWQAXICOPS9YBII as seed, the same msg_id we got from running send-header (IONONZOXVGTNGVEOCXPUI), "Test123" for payload, and yes for last packet (meaning we won’t send any other packets to this message).


4. Now let’s run the send-msg example. This command will send a header followed by a packet, which is the same behavior as running send-header and send-packet in sequence. These are the parameters that the executable expects:

# iota_mam_send_msg 
usage: send-msg <host> <port> <seed> <payload> <last_packet>

So let’s use as host, 14265 as port, ARDNWTPEAYOYQRDYPUACNWIWZPP9AHADVAJEAUBKDTLDMMHRNTLLHCSN9ODRFL9PHBTWQAXICOPS9YBII as seed, (IONONZOXVGTNGVEOCXPUI), "Test123" for payload, and yes for last packet.


5. Finally, let’s run the recv example. This command will read the message from some specific bundle. These are the parameters that the executable expects:

# iota_mam_recv 
usage: recv <host> <port> <bundle> <chid> (optional)

Let’s use as host, 14265 as port, the same bundle that was output from the last send-msg example (SLPCJIRDW9KUGPBXOFD99YIWPIAJKLQXHJOIPTDAEDHVEQVKRFETSABQZEGDWKAVEFZOU9YXVIS9NLGZX), and nothing for chid since it’s optional.

Payload: Test123

And voilà! We got the same payload ("Test123") that we had sent with send_msg!


This was another article to show the possibilities of the meta-iota OpenEmbedded layer.

I wanted to show how hardware that is commonly used for Industrial IoT applications can interact with the Tangle, this time by sending Masked Authenticated Messages. Like all the other tutorials, there should be enough flexibility so the steps listed here could be easily adapted into other kinds of hardware supported by the Yocto Project and OpenEmbedded.

If you have any questions or feedback, feel free to write a comment below, DM me on Discord (bernardoar#8478) or send me an email (


Bernardo Rodrigues

Written by

Embedded Software Developer & System Integrator. Yocto Project + OpenEmbedded + IOTA

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